{"id":71,"date":"2021-12-02T07:39:45","date_gmt":"2021-12-02T07:39:45","guid":{"rendered":"http:\/\/www.devblog.cn\/?p=71"},"modified":"2025-03-07T14:11:09","modified_gmt":"2025-03-07T06:11:09","slug":"71","status":"publish","type":"post","link":"http:\/\/www.devblog.cn\/?p=71","title":{"rendered":"Jetpack-LiveData\u6e90\u7801\u89e3\u6790"},"content":{"rendered":"

LiveData\u6e90\u7801\u89e3\u6790<\/h1>\n

\n \u6e90\u7801\u7248\u672c\uff1a
\n * \u6e90\u7801\u7248\u672c<\/strong>\uff1a2.8.7
\n * \u66f4\u65b0\u65f6\u95f4<\/strong>\uff1a2025-3\u6708
\n * \u9700\u4f1a\u4f7f\u7528<\/strong>\uff1aLifecycle<\/code><\/p>\n

\u5bfc\u822a\uff1a<\/strong>
\n * Jetpack-Lifecycle\u6e90\u7801\u89e3\u6790<\/a>
\n * Jetpack-LiveData\u6e90\u7801\u89e3\u6790<\/a>
\n * Jetpack-ViewModel\u6e90\u7801\u8be6\u89e3<\/a>
\n * \u66f4\u591a\u7684\u6587\u7ae0\u770b\u8fd9\u91cc\uff1a\u4e3b\u9875<\/a>\n<\/p><\/blockquote>\n

\u4f7f\u7528<\/h1>\n

\u76d1\u542c\u503c<\/h2>\n
val liveData = MutableLiveData<Int>()\nval observer = object : Observer<Int> {\n    override fun onChanged(value: Int) {\n        \/\/ \u6570\u636e\u6539\u53d8\n    }\n}\nliveData.observe(this, observer) \/\/ \u751f\u547d\u5468\u671f\u611f\u77e5\u89c2\u5bdf\nliveData.observeForever(observer) \/\/ \u6c38\u8fdc\u89c2\u5bdf\n<\/code><\/pre>\n
\u8bbe\u7f6e\u503c<\/h2>\n
liveData.setValue(value) \/\/ \u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b\nliveData.postValue(value) \/\/ \u5728\u540e\u53f0\u7ebf\u7a0b\n<\/code><\/pre>\n
\u83b7\u53d6\u503c<\/h2>\n
liveData.getValue() \/\/ \u83b7\u53d6\u503c\n<\/code><\/pre>\n
\u79fb\u9664\u76d1\u542c<\/h2>\n
liveData.removeObserver(observer) \/\/ \u79fb\u9664\u6307\u5b9a\u7684\u67d0\u4e2aObserver\nliveData.removeObservers(this) \/\/ \u79fb\u9664\u6307\u5b9aLifecycle\u7ed1\u5b9a\u7684\u6240\u6709Observer\n<\/code><\/pre>\n
\u662f\u5426<\/h2>\n
val initialized = liveData.isInitialized \/\/ \u662f\u5426\u521d\u59cb\u5316\nval hasObservers = liveData.hasObservers() \/\/ \u662f\u5426\u6709\u89c2\u5bdf\u8005\nval hasActiveObservers = liveData.hasActiveObservers() \/\/ \u662f\u5426\u6709\u6d3b\u8dc3\u7684\u89c2\u5bdf\u8005\n<\/code><\/pre>\n
\u6e90\u7801<\/h1>\n
\u6210\u5458\u53d8\u91cf<\/h2>\n
\/\/ \u6570\u636e\u9501\nfinal Object mDataLock = new Object();\n\/\/ \u5f00\u59cb\u7248\u672c\u53f7\nstatic final int START_VERSION = -1;\n\/\/ \u6ca1\u6709\u8bbe\u7f6e\u6570\u636e\u7684\u9ed8\u8ba4\u503c\nstatic final Object NOT_SET = new Object();\n\/\/ \u6240\u6709\u7684Observer\uff0ckey\u4e3a\u539f\u59cbObserver\uff0cvalue\u4e3a\u5305\u88c5\u540e\u7684Observer\u3002\nprivate SafeIterableMap<Observer<? super T>, ObserverWrapper> mObservers =\n        new SafeIterableMap<>();\n\/\/ \u6d3b\u52a8Observer\u7684\u6570\u91cf\nint mActiveCount = 0;\n\/\/ \u662f\u5426\u6d3b\u8dc3\u72b6\u6001\u6539\u53d8\u4e2d\nprivate boolean mChangingActiveState;\n\/\/ \u5f53\u524d\u6570\u636e\nprivate volatile Object mData;\n\/\/ \u5ef6\u8fdf\u7684\u6570\u636e\nvolatile Object mPendingData = NOT_SET;\n\/\/ \u5f53\u524d\u7248\u672c\u53f7\nprivate int mVersion;\n\n\/\/ \u662f\u5426\u503c\u5206\u53d1\u4e2d\nprivate boolean mDispatchingValue;\n\/\/ \u662f\u5426\u5206\u53d1\u65e0\u6548\nprivate boolean mDispatchInvalidated;\n\/\/ \u5ef6\u8fdf\u7684\u8d4b\u503c\uff0c\u8be6\u7ec6\u770b\u540e\u9762\u7684postValue()\u65b9\u6cd5\u6e90\u7801\u3002\nprivate final Runnable mPostValueRunnable = new Runnable() {\n    @SuppressWarnings(\"unchecked\")\n    @Override\n    public void run() {\n        Object newValue;\n        synchronized (mDataLock) {\n            newValue = mPendingData;\n            mPendingData = NOT_SET;\n        }\n        setValue((T) newValue);\n    }\n};\n<\/code><\/pre>\n
\u521b\u5efaLiveData<\/h2>\n
\/\/ \u6709\u9ed8\u8ba4\u503c\npublic LiveData(T value) {\n    \/\/ \u8bb0\u5f55\u8bbe\u7f6e\u7684\u503c\n    mData = value;\n    \/\/ \u7248\u672c\u53f7\u52a01\uff0c\u4ee5\u6807\u8bb0\u6b64LivaData\u7684\u6570\u636e\u7248\u672c\u8981\u6bd4Observer\u5305\u88c5\u8005\u7684\u6570\u636e\u7248\u672c\u8981\u9ad8\uff08\u65b0\uff09\uff0c\u4ee5\u8fdb\u884c\u901a\u77e5\u89c2\u5bdf\u8005Observer\u503c\u6539\u53d8\u3002\n    mVersion = START_VERSION + 1;\n}\n\n\/\/ \u65e0\u9ed8\u8ba4\u503c\npublic LiveData() {\n    \/\/ \u8bbe\u7f6e\u7684\u503c\u4e3a\u9ed8\u8ba4\n    mData = NOT_SET;\n    \/\/ \u7248\u672c\u53f7\u548cObserver\u5305\u88c5\u8005\u7684\u7248\u672c\u76f8\u540c\uff0c\u4ee5\u4e0d\u8fdb\u884c\u901a\u77e5\u89c2\u5bdf\u8005Observer\u503c\u6539\u53d8\u3002\n    mVersion = START_VERSION;\n}\n<\/code><\/pre>\n
\u76d1\u542c\u503c<\/h2>\n
observe()<\/h3>\n
@MainThread\npublic void observe(@NonNull LifecycleOwner owner, @NonNull Observer<? super T> observer) {\n    \/\/ \u65ad\u8a00\u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b\u8c03\u7528\uff0c\u5426\u5219\u629b\u5f02\u5e38\u3002\n    assertMainThread(\"observe\");\n    \/\/ \u5f53Lifecycle\u5904\u4e8eDESTROYED\u72b6\u6001\u65f6\uff0c\u518d\u89c2\u5bdf\u662f\u6ca1\u6709\u610f\u4e49\u7684\uff0c\u76f4\u63a5\u8fd4\u56de\u3002\n    if (owner.getLifecycle().getCurrentState() == DESTROYED) {\n        \/\/ ignore\n        return;\n    }\n    \/\/ \u521b\u5efa\u65b0\u7684Observer\u5305\u88c5\u8005LifecycleBoundObserver\uff0c\u8ba9\u5176\u76d1\u542c\u751f\u5468\u5468\u671f\u53d8\u5316\uff0c\u5e76\u5904\u7406\u3002\n    LifecycleBoundObserver wrapper = new LifecycleBoundObserver(owner, observer);\n    \/\/ mObservers\u662f\u4e00\u4e2aMap\uff0ckey\u4e3aObserver\uff0cvalue\u4e3aObserverWrapper\uff0c\u6301\u6709\u591a\u4e2a\u89c2\u5bdf\u8005\u5305\u88c5\u8005\u3002\n    \/\/ putIfAbsent\uff0c\u5982\u679c\u4f20\u5165key\u5bf9\u5e94\u7684value\u5df2\u7ecf\u5b58\u5728\uff0c\u5c31\u8fd4\u56de\u5b58\u5728\u7684value\uff0c\u4e0d\u8fdb\u884c\u66ff\u6362\u3002\u5982\u679c\u4e0d\u5b58\u5728\uff0c\u5c31\u6dfb\u52a0key\u548cvalue\uff0c\u5e76\u8fd4\u56denull\u3002\n    ObserverWrapper existing = mObservers.putIfAbsent(observer, wrapper);\n    if (existing != null && !existing.isAttachedTo(owner)) {\n        \/\/ \u8be5Observer\u5bf9\u8c61\u5df2\u7ecf\u88ab\u8be5LiveData\u6301\u6709\uff0c\u4e14\u8be5\u503cObserverWrapper\u5bf9\u8c61\u6ca1\u4f9d\u9644\u5230\u53c2\u6570owner\u7684Lifecycle\uff0c\n        \/\/ \u8bf4\u660e\u8be5Observer\u4e4b\u524d\u5df2\u7ecf\u88ab\u5176\u5b83\u7684Lifecycle\u6dfb\u52a0\uff0c\u518d\u88ab\u5f53\u524d\u7684Lifecycle\u6dfb\u52a0\uff0c\u5219\u76f4\u63a5\u629b\u51fa\u5f02\u5e38\u3002\n        throw new IllegalArgumentException(\"Cannot add the same observer\"\n                + \" with different lifecycles\");\n    }\n    if (existing != null) {\n        \/\/ \u8be5Observer\u5bf9\u8c61\u5df2\u7ecf\u88ab\u8be5LiveData\u6301\u6709\uff0c\u4e14\u8be5\u503cObserverWrapper\u5bf9\u8c61\u4f9d\u9644\u5230\u53c2\u6570owner\u7684Lifecycle\uff0c\u8bf4\u660e\u8be5Observer\u4e4b\u524d\u5df2\u7ecf\u88ab\u5f53\u524d\u7684Lifecycle\u6dfb\u52a0\uff0c\u5219\u76f4\u63a5\u8fd4\u56de\u3002\n        return;\n    }\n    \/\/ \u4f7f\u7528Lifecycle\u63a7\u4ef6\uff0c\u89c2\u5bdf\u8be5ObserverWrapper\u5bf9\u8c61\u751f\u547d\u5468\u671f\u3002\n    owner.getLifecycle().addObserver(wrapper);\n}\n<\/code><\/pre>\n
observe()<\/code>\u65b9\u6cd5\uff0c\u5c31\u662f\u628a\u6211\u4eec\u7684Observer<\/code>\u5bf9\u8c61\u5305\u88c5\u6210LifecycleBoundObserver<\/code>\u540e\u5b58\u5165mObservers<\/code>\u4e2d\uff0c\u5e76\u5c06\u5176\u6dfb\u52a0\u5230\u53c2\u6570owner<\/code>\u7684Lifecycle<\/code>\u4e2d\uff0c\u4ee5\u76d1\u542c\u751f\u547d\u5468\u671f\u53d8\u5316\u3002\u5b83\u7ee7\u627fObserverWrapper<\/code>\u5e76\u5b9e\u73b0\u4e86LifecycleEventObserver<\/code>\u3002<\/p>\n
\n  \u8bf4\u660e\uff1a<\/p>\n
    \n
  1. observe()<\/code>\u65b9\u6cd5\uff0c\u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b<\/strong>\u8c03\u7528\u3002<\/li>\n
  2. \u5f53Lifecycle<\/code>\u5904\u4e8eDESTROYED<\/code>\u72b6\u6001\u65f6\uff0c\u6b64\u65f6\u4e0d\u4f1a\u6dfb\u52a0<\/strong>\u3002<\/li>\n
  3. \u540c\u4e00\u4e2aLiveData<\/code>\uff0c\u65e0\u6cd5<\/strong>\u6dfb\u52a0\u5177\u6709\u4e0d\u540c\u7684<\/strong>Lifecycle<\/code>\u7684\u540c\u4e00\u4e2a<\/strong>Observer<\/code>\u3002<\/li>\n<\/ol>\n<\/blockquote>\n
    \u63a5\u4e0b\u6765\uff0c\u6211\u4eec\u5148\u770b\u4e00\u4e0bLifecycleBoundObserver<\/code>\u7684\u7236\u7c7b<\/strong>ObserverWrapper<\/code>\uff0c\u6700\u540e\u518d\u770b\u5b83\u3002<\/p>\n
    ObserverWrapper\u7c7b<\/strong><\/p>\n
    private abstract class ObserverWrapper {\n    \/\/ \u4f20\u5165\u7684\u539f\u59cb\u89c2\u5bdf\u8005\u5bf9\u8c61\n    final Observer<? super T> mObserver;\n    \/\/ \u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u662f\u5426\u5904\u4e8e\u6d3b\u8dc3\u72b6\u6001\uff0c\u53ea\u6709\u6d3b\u8dc3\u72b6\u6001\u7684\u65f6\u5019\u624d\u53ef\u4ee5\u88ab\u901a\u77e5\u3002\n    boolean mActive;\n    \/\/ \u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u6570\u636e\u7684\u7248\u672c\u53f7\u3002\n    int mLastVersion = START_VERSION;\n\n    ObserverWrapper(Observer<? super T> observer) {\n        \/\/ \u8bb0\u5f55\u4f20\u5165\u7684\u539f\u59cb\u89c2\u5bdf\u8005\u5bf9\u8c61\n        mObserver = observer;\n    }\n\n    \/\/ \u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u662f\u5426\u5904\u4e8e\u6d3b\u8dc3\u72b6\u6001\u3002\n    abstract boolean shouldBeActive();\n\n    \/\/ \u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u662f\u5426\u4f9d\u9644\u5230LifecycleOwner\u4e2d\u3002\n    boolean isAttachedTo(LifecycleOwner owner) {\n        return false;\n    }\n\n    \/\/ \u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u5206\u79bbObserver\uff0c\u5373\u4e0d\u518d\u89c2\u5bdf\u6b64ObserverWrapper\u3002\n    void detachObserver() {\n    }\n\n    \/\/ \u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u6d3b\u8dc3\u72b6\u6001\u6539\u53d8\u3002\n    void activeStateChanged(boolean newActive) {\n        if (newActive == mActive) {\n            \/\/ \u65b0\u72b6\u6001\u548c\u73b0\u6709\u72b6\u6001\u76f8\u540c\uff0c\u5219\u4e0d\u5904\u7406\u3002\n            return;\n        }\n        \/\/ \u7acb\u5373\u8bbe\u7f6e\u6d3b\u52a8\u72b6\u6001\uff0c\u8fd9\u6837\u6211\u4eec\u5c31\u6c38\u8fdc\u4e0d\u4f1a\u5411\u975e\u6d3b\u52a8\u6240\u6709\u8005\u5206\u6d3e\u4efb\u4f55\u5185\u5bb9\u3002\n        mActive = newActive;\n        \/\/ \u6539\u53d8\u6d3b\u8dc3\u89c2\u5bdf\u8005\u7684\u6570\u91cf\uff0c\u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u53d8\u6d3b\u8dc3+1\uff0c\u53d8\u975e\u6d3b\u8dc3-1\u3002\n        changeActiveCounter(mActive ? 1 : -1);\n        if (mActive) {\n            \/\/ \u6d3b\u8dc3\u72b6\u6001\u4e0b\uff0c\u8fdb\u884c\u5206\u53d1\u503c\u3002\n            dispatchingValue(this);\n        }\n    }\n}\n<\/code><\/pre>\n
    ObserverWrapper<\/code>\u7c7b\uff0c\u662f\u62bd\u8c61\u7c7b<\/strong>\uff0c\u4e3aObserver<\/code>\u7684\u5305\u88c5\u8005\uff0c\u5176\u5185\u90e8\u5bf9\u5176\u539f\u59cbObserver<\/code>\uff08observe()<\/code>\u3001observeForever()<\/code>\u4f20\u5165\uff09\u8fdb\u884c\u4e86\u5305\u88c5\u3002<\/p>\n
    \n  \u8bf4\u660e\uff1a<\/p>\n
      \n
    1. ObserverWrapper<\/code>\u5185\u90e8\u8fd8\u542b\u6709mLastVersion<\/code>\uff08\u6b64ObserverWrapper<\/code>\u6570\u636e\u7684\u7248\u672c\u53f7\uff09\uff0c\u7528\u4e8e\u5224\u65ad\u662f\u5426\u9700\u8981\u901a\u77e5\u6b64<\/strong>ObserverWrapper<\/code>\u6570\u636e\u6539\u53d8<\/strong>\uff0c\u8be6\u7ec6\u770b\u540e\u9762\u7684dispatchingValue()<\/code>\u65b9\u6cd5\u6e90\u7801\u3002 <\/li>\n
    2. activeStateChanged()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u6d3b\u8dc3\u72b6\u6001\u6539\u53d8\uff0c\u5185\u90e8\u5224\u65ad\u4e86\u5982\u679c\u65b0\u72b6\u6001<\/strong>\u548c\u73b0\u6709\u72b6\u6001<\/strong>\u76f8\u540c\u5219\u4e0d\u5904\u7406\uff0c\u5e76\u4e14\u5176\u5185\u90e8\u4ec5\u4f1a\u5728\u6d3b\u8dc3\u72b6\u6001<\/strong>\u4e0b\u8c03\u7528dispatchingValue()<\/code>\u65b9\u6cd5\u4ee5\u8fdb\u884c\u5206\u53d1\u6b64<\/strong>ObserverWrapper<\/code>\u7684\u503c\u3002<\/li>\n<\/ol>\n<\/blockquote>\n
      \u63a5\u4e0b\u6765\uff0c\u6211\u4eec\u770b\u4e0bLifecycleBoundObserver<\/code>\u7c7b\uff0c\u7136\u540e\u518d\u4f9d\u6b21\u770b\u4e0a\u9762\u7528\u5230\u7684changeActiveCounter()<\/code>\u3001dispatchingValue()<\/code>\u65b9\u6cd5\u3002<\/p>\n
      LifecycleBoundObserver\u7c7b<\/strong><\/p>\n
      class LifecycleBoundObserver extends ObserverWrapper implements LifecycleEventObserver {\n    \/\/ \u4f20\u5165\u7684Lifecycle\u6301\u6709\u8005\u5bf9\u8c61\n    @NonNull\n    final LifecycleOwner mOwner;\n\n    LifecycleBoundObserver(@NonNull LifecycleOwner owner, Observer<? super T> observer) {\n        super(observer);\n        mOwner = owner;\n    }\n\n    \/\/ \u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u662f\u5426\u5e94\u8be5\u5904\u4e8e\u6d3b\u8dc3\u72b6\u6001\u3002\n    @Override\n    boolean shouldBeActive() {\n        \/\/ onStart\uff0conResume\uff0conPause\u8fd9\u4e09\u4e2a\u72b6\u6001\u5904\u4e8e\u6d3b\u8dc3\u72b6\u6001\uff0c\u5176\u5b83\u5904\u4e8e\u975e\u6d3b\u8dc3\u72b6\u6001\u3002\n        return mOwner.getLifecycle().getCurrentState().isAtLeast(STARTED);\n    }\n\n    \/\/ LifecycleEventObserver\u63a5\u53e3\u5b9e\u73b0\u65b9\u6cd5\uff0c\u751f\u547d\u5468\u671f\u72b6\u6001\u6539\u53d8\u7684\u65f6\u5019\u4f1a\u6536\u5230\u901a\u77e5\u3002\n    @Override\n    public void onStateChanged(@NonNull LifecycleOwner source,\n            @NonNull Lifecycle.Event event) {\n        Lifecycle.State currentState = mOwner.getLifecycle().getCurrentState();\n        if (currentState == DESTROYED) {\n            \/\/ \u5f53\u751f\u547d\u5468\u671f\u72b6\u6001\u4e3adestroyed\u7684\u65f6\u5019\uff0c\u628a\u8be5\u89c2\u5bdf\u8005\u81ea\u52a8\u79fb\u9664\u3002\n            \/\/ -\u8bf4\u660e\uff1a\u5728removeObserver\u5185\u90e8\uff0c\u4f1a\u8c03\u7528\u4e0b\u9762\u7684detachObserver\u65b9\u6cd5\uff0c\u5c06\u6b64ObserverWrapper\u4eceLifecycle\u4e2d\u79fb\u9664\uff0c\n            \/\/ -\u5e76\u8c03\u7528\u7236\u7c7b\u7684activeStateChanged\u65b9\u6cd5\uff0c\u901a\u77e5\u6d3b\u8dc3\u72b6\u6001\u6539\u4e3a\uff1a\u975e\u6d3b\u8dc3\u7684\u3002\n            removeObserver(mObserver);\n            return;\n        }\n        \/\/ \u751f\u547d\u5468\u671f\u72b6\u6001\u6539\u53d8\uff0c\u901a\u77e5\u6d3b\u8dc3\u72b6\u6001\u6539\u53d8\u3002\n        \/\/ \u8bf4\u660e\uff1a\u52a0While\u5faa\u73af\u7684\u76ee\u7684\uff0c\u9632\u6b62\u6267\u884cactiveStateChanged\u7684\u65f6\u5019\uff0cmOwner\u7684\u751f\u547d\u5468\u671f\u7684\u72b6\u6001\u66f4\u6539\u3002\n        Lifecycle.State prevState = null;\n        while (prevState != currentState) {\n            prevState = currentState;\n            \/\/ \u901a\u77e5\u6d3b\u8dc3\u72b6\u6001\u6539\u53d8\n            activeStateChanged(shouldBeActive());\n            \/\/ \u8bb0\u5f55\u5f53\u524d\u72b6\u6001\n            currentState = mOwner.getLifecycle().getCurrentState();\n        }\n    }\n\n    \/\/ \u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u662f\u5426\u4f9d\u9644\u5230LifecycleOwner\u4e2d\u3002\n    @Override\n    boolean isAttachedTo(LifecycleOwner owner) {\n        \/\/ \u5982\u679c\u6301\u6709\u7684\uff08observe()\u65b9\u6cd5\u4f20\u5165\u7684\uff09mOwner\u4e0e\u8981\u6bd4\u8f83\u7684owner\u76f8\u540c\uff0c\u5219\u8ba4\u4e3a\u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u5df2\u7ecf\u4f9d\u9644\u5230\u4f20\u5165\u7684LifecycleOwner\u4e2d\u3002\n        return mOwner == owner;\n    }\n\n    \/\/ \u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u5206\u79bbObserver\uff0c\u5373\u4e0d\u518d\u89c2\u5bdf\u6b64ObserverWrapper\u3002\n    @Override\n    void detachObserver() {\n        \/\/ Lifecycle\u79fb\u9664\u6b64ObserverWrapper\n        mOwner.getLifecycle().removeObserver(this);\n    }\n}\n<\/code><\/pre>\n
      LifecycleBoundObserver<\/code>\u7c7b\uff0c\u662fObserverWrapper<\/code>\u5b50\u7c7b\uff0c\u5185\u90e8\u5b9e\u73b0\u4e86LifecycleEventObserver<\/code>\uff08\u5b9e\u73b0\u4e86\u6b64\u624d\u80fd\u88abobserve()<\/code>\u65b9\u6cd5\u5185\u7684Lifecycle<\/code>\u6dfb\u52a0\uff0c\u7528\u4e8e\u76d1\u542cLifecycle<\/code>\u72b6\u6001\u6539\u53d8\uff09\uff0c\u4e3a\u548c\u751f\u547d\u5468\u671f\u7ed1\u5b9a<\/strong>\u7684Observer<\/code>\u3002<\/p>\n
      \n  \u8bf4\u660e\uff1a<\/p>\n
        \n
      1. \u6b64\u7c7b\u5185\u90e8\u542b\u6709LifecycleOwner<\/code>\uff0c\u4e3aobserve()<\/code>\u65b9\u6cd5owner<\/code>\u53c2\u6570\u4f20\u5165\u3002<\/li>\n
      2. shouldBeActive()<\/code>\u65b9\u6cd5\uff0c\u7528\u4e8e\u5224\u65ad\u6b64ObserverWrapper<\/code>\u662f\u5426\u5904\u4e8e\u6d3b\u8dc3<\/strong>\u72b6\u6001\uff0c\u5176\u5185\u90e8\u5224\u65ad\u4e3a\u6b64Lifecycle<\/code>\u7684\u5f53\u524d\u751f\u547d\u5468\u671f\u72b6\u6001<\/strong>\u5927\u4e8e\u7b49\u4e8eSTARTED<\/code>\u5373\u4e3a\u6d3b\u8dc3<\/strong>\u72b6\u6001\uff08\u5373\uff1aonStart<\/code>\uff0conResume<\/code>\uff0conPause<\/code>\u4e3a\u6d3b\u8dc3\u72b6\u6001<\/strong>\uff0c\u5176\u5b83\u4e3a\u975e\u6d3b\u8dc3\u72b6\u6001<\/strong>\uff09\u3002<\/li>\n
      3. onStateChanged()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u5f53\u751f\u547d\u5468\u671f\u72b6\u6001\u6539\u53d8<\/strong>\u7684\u65f6\u5019\uff0c\u901a\u77e5\u6b64\u65b9\u6cd5\u3002\n
          \n
        1. \u72b6\u6001\u4e3adestroyed<\/code>\u7684\u65f6\u5019\uff0c\u4f1a\u8c03\u7528removeObserver()<\/code>\u65b9\u6cd5\u5220\u9664\u3002\u6b64\u65b9\u6cd5\u5185\u90e8\u8c03\u7528\u4e86\u6b64ObserverWrapper<\/code>\u7684detachObserver()<\/code>\u65b9\u6cd5\uff0c\u5c06\u6b64Observer<\/code>\u4eceLifecycle<\/code>\u4e2d\u79fb\u9664\uff0c\u8fd8\u4f1a\u8c03\u7528\u6b64ObserverWrapper<\/code>\u7684activeStateChanged()<\/code>\u65b9\u6cd5\uff0c\u901a\u77e5\u6d3b\u8dc3\u72b6\u6001\u4e3a\u975e\u6d3b\u8dc3\u7684<\/strong>\u3002removeObserver()<\/code>\u76f8\u5173\uff0c\u8bf7\u770b\u4e0b\u9762\u7684\u79fb\u9664\u76d1\u542c<\/strong>–removeObserver()<\/code>\u3002<\/li>\n
        2. \u72b6\u6001\u4e3a\u5176\u5b83<\/strong>\u7684\u65f6\u5019\uff0c\u4f1a\u8c03\u7528activeStateChanged()<\/code>\u65b9\u6cd5\uff0c\u901a\u77e5\u6d3b\u8dc3\u72b6\u6001\u6539\u53d8<\/strong>\uff0c\u6b64\u65b9\u6cd5\u4ec5\u4f1a\u5728\u6d3b\u8dc3\u72b6\u6001<\/strong>\u4e0b\u8fdb\u884c\u5206\u53d1\u503c\u3002<\/li>\n<\/ol>\n<\/li>\n
        3. \u7531\u4e8eLifecycle<\/code>\u5728\u589e\u52a0LifecycleEventObserver<\/code>\u65f6\uff0c\u4f1a\u5728onStateChanged()<\/code>\u7acb\u5373\u6536\u5230\u63a5\u6536\u5230\u5f53\u524d\u7684\u72b6\u6001\uff0c\u6240\u4ee5\u540c\u4e00\u4e2a<\/strong>LiveData<\/code>\uff0c\u5728observe()<\/code>\u4e4b\u524d\u53d1\u7684\u6570\u636e\uff0c\u5728\u91cd\u65b0observe()<\/code>\u65f6\u4e5f\u4f1a\u63a5\u6536\u5230\u4e4b\u524d\u53d1\u7684\uff0c\u6b64\u4e3a\u7c98\u6027\u6548\u679c<\/strong>\uff08\u4e4b\u524d\u53d1\u9001\u7684\u6570\u636e\uff0c\u5728\u91cd\u65b0\u8ba2\u9605\u540e<\/strong>\uff0c\u4f1a\u91cd\u65b0\u83b7\u53d6\u5230\uff09\u3002<\/li>\n<\/ol>\n<\/blockquote>\n
          \u63a5\u4e0b\u6765\uff0c\u6211\u4eec\u6765\u770b\u4e00\u4e0bObserverWrapper<\/code>\u7c7bactiveStateChanged()<\/code>\u65b9\u6cd5\u7528\u5230\u7684changeActiveCounter()<\/code>\u65b9\u6cd5\u3002<\/p>\n
          LiveData –> changeActiveCounter()\u65b9\u6cd5<\/strong><\/p>\n
          @MainThread\nvoid changeActiveCounter(int change) {\n    \/\/ \u8bb0\u5f55\u4e4b\u524d\u6d3b\u8dc3\u7684\u6570\u91cf\n    int previousActiveCount = mActiveCount;\n    \/\/ \u8bb0\u5f55\u73b0\u5728\u7684\u6d3b\u8dc3\u7684\u6570\u91cf\uff0cchange\uff1a\u6d3b\u8dc3\u72b6\u6001\u4e3a+1\uff0c\u975e\u6d3b\u8dc3\u72b6\u6001\u4e3a-1\u3002\n    mActiveCount += change;\n    if (mChangingActiveState) {\n        \/\/ \u5982\u679c\u662f\u6539\u53d8\u4e2d\uff0c\u5219\u8fd4\u56de\uff0c\u56e0\u4e3a\u6709\u4e0b\u9762\u7684while\u5904\u7406\u53d8\u5316\u3002\n        return;\n    }\n    \/\/ \u6807\u8bb0\u4e3a\u6539\u53d8\u4e2d\n    mChangingActiveState = true;\n    try {\n        \/\/ \u4e4b\u524d\u7684\u6d3b\u8dc3\u6570\u91cf\u548c\u73b0\u5728\u7684\u6d3b\u8dc3\u6570\u91cf\u4e0d\u4e00\u81f4\uff0c\u90a3\u4e48\u5c06\u6267\u884c\u4e0b\u9762\u7684\u901a\u77e5onActive()\u6216\u8005onInactive()\u3002\n        \/\/ \u8bf4\u660e\uff1a\u52a0while\u7684\u539f\u56e0\uff0c\u56e0\u4e3a\u5f53\u6267\u884c\u4e0b\u9762\u5224\u65ad\u903b\u8f91\u7684\u65f6\u5019\uff0cchangeActiveCounter()\u65b9\u6cd5\u518d\u6b21\u8c03\u7528\uff0c\u5bfc\u81f4mActiveCount\u503c\u66f4\u6539\uff0c\u6240\u4ee5\u52a0while\u4f7f\u5176\u4fdd\u6301\u4e00\u81f4\u3002\n        while (previousActiveCount != mActiveCount) {\n            \/\/ \u4e4b\u524d\u7684\u6d3b\u8dc3\u6570\u91cf\u4e3a0\uff0c\u5e76\u4e14\u73b0\u5728\u7684\u6d3b\u8dc3\u6570\u91cf\u5927\u4e8e0\uff0c\u5373\u8bf4\u660e\u4e4b\u524d\u662f\u975e\u6d3b\u8dc3\u72b6\u6001\uff0c\u7136\u540e\u73b0\u5728\u662f\u6d3b\u8dc3\u72b6\u6001\uff0c\u5219\u9700\u8981\u8c03\u7528onActive()\u65b9\u6cd5\u3002\n            boolean needToCallActive = previousActiveCount == 0 && mActiveCount > 0;\n            \/\/ \u4e4b\u524d\u7684\u6d3b\u8dc3\u6570\u91cf\u662f\u5927\u4e8e0\uff0c\u5e76\u4e14\u73b0\u5728\u7684\u6d3b\u8dc3\u6570\u91cf\u4e3a0\uff0c\u5373\u8bf4\u660e\u4e4b\u524d\u662f\u6d3b\u8dc3\u72b6\u6001\uff0c\u7136\u540e\u73b0\u5728\u662f\u975e\u6d3b\u8dc3\u72b6\u6001\uff0c\u5219\u9700\u8981\u8c03\u7528onInactive()\u65b9\u6cd5\u3002\n            boolean needToCallInactive = previousActiveCount > 0 && mActiveCount == 0;\n            \/\/ \u66f4\u65b0\u4e4b\u524d\u7684\u4e3a\u73b0\u5728\u7684\n            previousActiveCount = mActiveCount;\n            if (needToCallActive) {\n                \/\/ \u9700\u8981\u8c03\u7528onActive()\u65b9\u6cd5\uff0c\u5b83\u662f\u7a7a\u65b9\u6cd5\uff0c\u53ef\u4ee5\u81ea\u5b9a\u4e49LiveData\u8986\u76d6\u5b9e\u73b0\u3002\n                onActive();\n            } else if (needToCallInactive) {\n                \/\/ \u9700\u8981\u8c03\u7528onInactive()\u65b9\u6cd5\uff0c\u5b83\u662f\u7a7a\u65b9\u6cd5\uff0c\u53ef\u4ee5\u81ea\u5b9a\u4e49LiveData\u8986\u76d6\u5b9e\u73b0\u3002\n                onInactive();\n            }\n        }\n    } finally {\n        \/\/ \u6807\u8bb0\u4e3a\u6539\u53d8\u7ed3\u675f\n        mChangingActiveState = false;\n    }\n}\n<\/code><\/pre>\n
          changeActiveCounter()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u6539\u53d8\u6d3b\u8dc3\u89c2\u5bdf\u8005<\/strong>\u7684\u6570\u91cf\uff0c\u5e76\u4f1a\u901a\u77e5\u6b64LiveData<\/code>\u7684onActive()<\/code>\uff08\u4e0d\u6d3b\u8dc3\u53d8\u6d3b\u8dc3\uff09\u6216\u8005onInactive()<\/code>\uff08\u6d3b\u8dc3\u53d8\u4e0d\u6d3b\u8dc3\uff09\u3002<\/p>\n
          \u63a5\u4e0b\u6765\uff0c\u6211\u4eec\u6765\u770b\u4e00\u4e0bObserverWrapper<\/code>\u7c7bactiveStateChanged()<\/code>\u65b9\u6cd5\u7528\u5230\u7684dispatchingValue()<\/code>\u65b9\u6cd5\u3002<\/p>\n
          LiveData –> dispatchingValue()\u65b9\u6cd5<\/strong><\/p>\n
          void dispatchingValue(@Nullable ObserverWrapper initiator) {\n    if (mDispatchingValue) {\n        \/\/ \u5206\u53d1\u503c\u4e2d\uff0c\u5219\u6807\u8bb0\u5206\u53d1\u5931\u6548\uff0c\u5e76\u8fd4\u56de\uff08\u56e0\u4e3a\u6709\u4e0b\u9762\u7684do-while\u5904\u7406\u53d8\u5316\uff09\u3002\n        mDispatchInvalidated = true;\n        return;\n    }\n    \/\/ \u6807\u8bb0\u5206\u53d1\u503c\u4e2d\n    mDispatchingValue = true;\n    do {\n        \/\/ \u6e05\u7a7a\u5206\u53d1\u5931\u6548\u7684\u6807\u8bb0\n        mDispatchInvalidated = false;\n        if (initiator != null) {\n            \/\/ initiator\u4e0d\u4e3a\u7a7a\uff0c\u4e3aactiveStateChanged()\u65b9\u6cd5\u8c03\u7528\u4f20\u5165\uff0c\u5219\u53ea\u901a\u77e5\u8be5ObserverWrapper\u3002\n            \/\/ \u8003\u8651\u901a\u77e5\n            considerNotify(initiator);\n            \/\/ \u76f4\u63a5\u6e05\u7a7a\u6807\u8bb0\n            initiator = null;\n        } else {\n            \/\/ initiator\u4e3a\u7a7a\uff0c\u4e3asetValue()\u65b9\u6cd5\u8c03\u7528\uff0c\u5219\u901a\u77e5\u6240\u6709\u7684ObserverWrapper\u3002\n            for (Iterator<Map.Entry<Observer<? super T>, ObserverWrapper>> iterator =\n                    mObservers.iteratorWithAdditions(); iterator.hasNext(); ) {\n                \/\/ \u8003\u8651\u901a\u77e5\n                considerNotify(iterator.next().getValue());\n                \/\/ \u5728\u904d\u5386\u8fc7\u7a0b\u4e2d\uff0c\u5982\u679c\u9047\u5230\u503c\u66f4\u65b0\uff08dispatchingValue()\u8c03\u7528\uff09\uff0c\u5219\u7acb\u5373\u9000\u51fa\u5f53\u524d\u5206\u53d1\uff0c\u5219\u7ee7\u7eed\u8d70while\uff0c\u518d\u6267\u884cdo\u4e2d\u903b\u8f91\u3002\n                if (mDispatchInvalidated) {\n                    break;\n                }\n            }\n        }\n    } while (mDispatchInvalidated);\n    \/\/ \u6807\u8bb0\u5206\u53d1\u503c\u7ed3\u675fLiveData\u6e90\u7801\u89e3\u6790\n    mDispatchingValue = false;\n}\n<\/code><\/pre>\n
          dispatchingValue()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u5206\u53d1\u503c<\/strong>\u65b9\u6cd5\uff0c\u5982\u679c\u53c2\u6570initiator<\/code>\u4e0d\u4e3a\u7a7a<\/strong>\u5219\u53ea\u901a\u77e5<\/strong>\u6b64ObserverWrapper<\/code>\u5206\u53d1\u503c\uff0c\u5982\u679c\u53c2\u6570initiator<\/code>\u4e3a\u7a7a<\/strong>\u5219\u901a\u77e5\u6b64LiveData<\/code>\u6240\u6709<\/strong>\u7684ObserverWrapper<\/code>\u5206\u53d1\u503c\u3002<\/p>\n
          \u63a5\u4e0b\u6765\uff0c\u6211\u4eec\u6765\u770b\u4e00\u4e0bdispatchingValue()<\/code>\u65b9\u6cd5\u7528\u5230\u7684considerNotify()<\/code>\u65b9\u6cd5\u3002<\/p>\n
          LiveData –> considerNotify\u65b9\u6cd5<\/strong><\/p>\n
          @SuppressWarnings(\"unchecked\")\nprivate void considerNotify(ObserverWrapper observer) {\n    if (!observer.mActive) {\n        \/\/ \u975e\u6d3b\u8dc3\u72b6\u6001\uff08\u4ec5setValue()\u901a\u77e5\u6240\u6709ObserverWrapper\u5206\u53d1\u4f20\u5165\uff0c\u624d\u4f1a\u6709\u6b64\u4e3a\u4e0d\u6d3b\u8dc3\u72b6\u6001\uff09\uff0c\u5219\u4e0d\u8fdb\u884c\u540e\u7eed\u5904\u7406\u3002\n        return;\n    }\n    if (!observer.shouldBeActive()) {\n        \/\/ shouldBeActive()\u4e3a\u975e\u6d3b\u8dc3\u72b6\u6001\uff0c\u4e0d\u8fdb\u884c\u540e\u7eed\u5904\u7406\u3002\n        observer.activeStateChanged(false);\n        return;\n    }\n    if (observer.mLastVersion >= mVersion) {\n        \/\/ \u6b64Observer\u6570\u636e\u7684\u7248\u672c\u53f7[\u5927\u4e8e\u7b49\u4e8e]\u5f53\u524dLiveData\u6570\u636e\u7684\u7248\u672c\u53f7\uff0c\u5219\u8bf4\u660e\u6570\u636e\u5df2\u7ecf\u540c\u6b65\uff0c\u5219\u4e0d\u8fdb\u884c\u540e\u7eed\u5904\u7406\u3002\n        return;\n    }\n    \/\/ \u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u66f4\u65b0\u7248\u672c\u53f7\u3002\n    observer.mLastVersion = mVersion;\n    \/\/ \u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u901a\u77e5\u4f20\u5165\u7684\u89c2\u5bdf\u8005\uff0c\u6570\u636e\u6539\u53d8\u3002\n    observer.mObserver.onChanged((T) mData);\n}\n<\/code><\/pre>\n
          considerNotify()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u8003\u8651\u901a\u77e5<\/strong>\u65b9\u6cd5\uff0c\u5176\u5185\u90e8\u5224\u65ad<\/strong>\u4e86\u6b64observer<\/code>\u975e\u6d3b\u8dc3\u72b6\u6001\u4e0d\u901a\u77e5<\/strong>\uff0c\u6b64observer<\/code>\u6570\u636e\u7248\u672c\u53f7<\/strong>\u5927\u4e8e\u7b49\u4e8e\u5f53\u524dLiveData<\/code>\u6570\u636e\u7684\u7248\u672c\u53f7\u4e0d\u901a\u77e5<\/strong>\uff08\u8bf4\u660e\u6b64observer<\/code>\u6570\u636e\u5df2\u7ecf\u662f\u6700\u65b0\u7684\uff09\uff0c\u5176\u4f59\u5219\u66f4\u65b0<\/strong>\u6b64observer<\/code>\u7684\u7248\u672c\u53f7<\/strong>\u4e3a\u5f53\u524d<\/strong>LiveData<\/code>\u6570\u636e\u6700\u65b0\u7684\u7248\u672c\u53f7<\/strong>\uff08\u4ee5\u6807\u8bb0\u5f53\u524dObserverWrapper<\/code>\u5df2\u7ecf\u6570\u636e\u6700\u65b0\uff09\u3001\u901a\u77e5<\/strong>\u53c2\u6570\u7684observer<\/code>\u6570\u636e\u6539\u53d8<\/strong>\uff08\u4f20\u5165\u6700\u65b0\u7684\u6570\u636e\uff09\u3002<\/p>\n
          \u5c0f\u7ed3<\/h4>\n
          \n  \u4ee3\u7801\u6d41\u7a0b\uff1a<\/p>\n
            \n
          1. LiveData<\/code>\u7684observe(owner, observer)<\/code>\u65b9\u6cd5\uff0c\u5c06\u53c2\u6570observer<\/code>\u5305\u88c5\u6210LifecycleBoundObserver<\/code>\u540e\u6dfb\u52a0\u5230mObservers<\/code>\uff0c\u5e76\u6dfb\u52a0\u5230\u53c2\u6570owner<\/code>\u7684Lifecycle<\/code>\u4e2d\uff0c\u4ee5\u76d1\u542c\u751f\u547d\u5468\u671f\u53d8\u5316<\/strong>\u3002<\/li>\n
          2. \u5f53\u751f\u547d\u5468\u671f\u72b6\u6001\u6539\u53d8<\/strong>\u7684\u65f6\u5019\uff0c\u901a\u77e5LifecycleBoundObserver<\/code>\u7684onStateChanged<\/code>\u65b9\u6cd5\u3002\n
              \n
            1. \u72b6\u6001\u4e3adestroyed<\/code>\u7684\u65f6\u5019\uff0c\u5c06\u6b64LifecycleBoundObserver<\/code>\u4eceLifecycle<\/code>\u4e2d\u79fb\u9664\u3002<\/li>\n
            2. \u72b6\u6001\u4e3a\u5176\u5b83<\/strong>\u7684\u65f6\u5019\uff0c\u4f1a\u8c03\u7528LifecycleBoundObserver<\/code>\u7236\u7c7bObserverWrapper<\/code>\u7684activeStateChanged()<\/code>\u65b9\u6cd5\uff0c\u901a\u77e5\u6d3b\u8dc3\u72b6\u6001<\/strong>\u6539\u53d8\uff08onStart<\/code>\u3001onResume<\/code>\u3001onPause<\/code>\u4e3a\u6d3b\u8dc3<\/strong>\uff0c\u5176\u5b83\u4e3a\u975e\u6d3b\u8dc3<\/strong>\uff09\u3002<\/li>\n<\/ol>\n<\/li>\n
            3. ObserverWrapper<\/code>\u7684activeStateChanged()<\/code>\u65b9\u6cd5\uff0c\u4f1a\u5224\u65ad\u65b0\u72b6\u6001\u548c\u73b0\u6709\u72b6\u6001\u76f8\u540c<\/strong>\uff0c\u5219\u4e0d\u5904\u7406<\/strong>\u3002\u5e76\u8c03\u7528LiveData<\/code>\u7684changeActiveCounter()<\/code>\u65b9\u6cd5\uff08\u6539\u53d8\u6d3b\u8dc3\u89c2\u5bdf\u8005<\/strong>\u7684\u6570\u91cf\uff09\uff1b\u4ee5\u53ca\u5982\u679c\u901a\u77e5\u7684\u662f\u6d3b\u8dc3\u72b6\u6001<\/strong>\uff0c\u5219\u8c03\u7528LiveData<\/code>\u7684dispatchingValue()<\/code>\u65b9\u6cd5\uff08\u5206\u53d1\u503c\uff09\u3002\n
                \n
              1. LiveData<\/code>\u7684changeActiveCounter()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u6539\u53d8\u6d3b\u8dc3\u89c2\u5bdf\u8005<\/strong>\u7684\u6570\u91cf\uff0c\u5e76\u4f1a\u901a\u77e5\u6b64LiveData<\/code>\u7684onActive()<\/code>\uff08\u6d3b\u8dc3\uff09\u6216\u8005onInactive()<\/code>\uff08\u4e0d\u6d3b\u8dc3\uff09\u3002<\/li>\n
              2. LiveData<\/code>\u7684dispatchingValue(initiator)<\/code>\u65b9\u6cd5\uff0c\u4e3a\u5206\u53d1\u503c<\/strong>\u65b9\u6cd5\uff0c\u5982\u679c\u662f\u6d3b\u8dc3\u72b6\u6001\u6539\u53d8<\/strong>\u800c\u5206\u53d1\u503c\uff08\u53c2\u6570initiator<\/code>\u4e0d\u4e3a\u7a7a<\/strong>\uff09\uff0c\u5219\u76f4\u63a5\u8ba9\u6b64<\/strong>ObserverWrapper<\/code>\u8003\u8651\u901a\u77e5\uff08\u8c03\u7528LiveData<\/code>\u7684considerNotify()<\/code>\u65b9\u6cd5\uff09\u3002\u5982\u679c\u662fsetValue()<\/code>\u800c\u5206\u53d1\u503c\uff08\u53c2\u6570initiator<\/code>\u4e3a\u7a7a<\/strong>\uff09\uff0c\u5219\u8ba9\u6240\u6709\u7684<\/strong>ObserverWrapper<\/code>\u8003\u8651\u901a\u77e5\u3002<\/li>\n<\/ol>\n<\/li>\n
              3. LiveData<\/code>\u7684considerNotify(observer)<\/code>\u65b9\u6cd5\uff0c\u4f1a\u8fdb\u884c\u6700\u7ec8\u7684\u5224\u65ad\uff0c\u5982\u679c\u6b64observer<\/code>\u662f\u6d3b\u8dc3<\/strong>\u7684\uff0c\u5e76\u4e14\u6b64observer<\/code>\u7684\u6570\u636e\u7248\u672c\u53f7\u8fc7\u4f4e<\/strong>\uff0c\u5219\u8fdb\u884c\u901a\u77e5\u6570\u636e\u6539\u53d8<\/strong>\u5e76\u4f20\u5165\u6700\u65b0<\/strong>\u7684\u6570\u636e\u3002<\/li>\n<\/ol>\n
                  LiveData<\/code>\u7684observe(owner, observer)<\/code>\u65b9\u6cd5\u6ce8\u91ca\uff1a<\/p>\n
                  \n
                1. \u5728\u7ed9\u5b9a\u7684owner<\/code>\u7684\u751f\u547d\u5468\u671f\u5185\uff0c\u5c06\u7ed9\u5b9a\u7684observer<\/code>\u6dfb\u52a0\u5230\u89c2\u5bdf\u8005\u5217\u8868\u4e2d\u3002\u4e8b\u4ef6\u5728\u4e3b\u7ebf\u7a0b<\/strong>\u4e0a\u5206\u6d3e\u3002\u5982\u679cLiveData<\/code>\u5df2\u7ecf\u6709\u6570\u636e\u8bbe\u7f6e\uff0c\u5b83\u5c06\u88ab\u4f20\u9012\u7ed9\u6b64observer<\/code>\u3002observer<\/code>\u53ea\u6709\u5728owner<\/code>\u5904\u4e8eSTARTED<\/code>\u6216RESUMED<\/code>\u72b6\u6001\uff08\u6d3b\u52a8\uff09\u65f6\u624d\u4f1a\u63a5\u6536\u4e8b\u4ef6<\/strong>\u3002<\/li>\n
                2. \u5982\u679cowner<\/code>\u79fb\u52a8\u5230DESTROYED<\/code>\u72b6\u6001\uff0cobserver<\/code>\u5c06\u81ea\u52a8\u88ab\u79fb\u9664<\/strong>\u3002<\/li>\n
                3. \u5f53\u6570\u636e\u53d1\u751f\u53d8\u5316\u800cowner<\/code>\u4e0d\u6d3b\u52a8\u65f6\uff0c\u5b83\u5c06\u4e0d\u4f1a\u6536\u5230\u4efb\u4f55\u66f4\u65b0\u3002\u5982\u679c\u5b83\u518d\u6b21\u6fc0\u6d3b\uff0c\u5b83\u5c06\u81ea\u52a8\u63a5\u6536\u6700\u540e\u53ef\u7528\u7684\u6570\u636e<\/strong>\u3002<\/li>\n
                4. \u53ea\u8981\u7ed9\u5b9a\u7684LifecycleOwner<\/code>\u6ca1\u6709\u88ab\u9500\u6bc1\uff0cLiveData<\/code>\u5c31\u4f1a\u4fdd\u6301\u5bf9observer<\/code>\u548cowner<\/code>\u7684\u5f3a\u5f15\u7528\u3002\u5f53\u5b83\u88ab\u9500\u6bc1\u65f6\uff0cLiveData<\/code>\u4f1a\u5220\u9664\u5bf9observer<\/code>\u548cowner<\/code>\u7684\u5f15\u7528\u3002\u5982\u679c\u7ed9\u5b9a\u7684owner<\/code>\u5df2\u7ecf\u5904\u4e8eDESTROYED<\/code>\u72b6\u6001\uff0cLiveData<\/code>\u5ffd\u7565\u8c03\u7528\u3002<\/li>\n
                5. \u5982\u679c\u7ed9\u5b9a\u7684owner<\/code>\u89c2\u5bdf\u8005\u5143\u7ec4\u5df2\u7ecf\u5728\u5217\u8868\u4e2d\uff0c\u8c03\u7528\u5c06\u88ab\u5ffd\u7565\u3002\u5982\u679cobserver<\/code>\u5df2\u7ecf\u4e0e\u53e6\u4e00\u4e2aowner<\/code>\u5728\u5217\u8868\u4e2d\uff0cLiveData<\/code>\u629b\u51fa\u4e00\u4e2aIllegalArgumentException<\/code>\u3002<\/li>\n<\/ol>\n<\/blockquote>\n
                  observeForever()<\/h3>\n
                  @MainThread\npublic void observeForever(@NonNull Observer<? super T> observer) {\n    \/\/ \u65ad\u8a00\u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b\u8c03\u7528\uff0c\u5426\u5219\u629b\u5f02\u5e38\u3002\n    assertMainThread(\"observeForever\");\n    \/\/ \u521b\u5efa\u65b0\u7684Observer\u5305\u88c5\u8005AlwaysActiveObserver\uff0c\u8ba9\u5176\u5904\u7406\u3002\n    AlwaysActiveObserver wrapper = new AlwaysActiveObserver(observer);\n    ObserverWrapper existing = mObservers.putIfAbsent(observer, wrapper);\n    if (existing instanceof LiveData.LifecycleBoundObserver) {\n        \/\/ \u8be5Observer\u5bf9\u8c61\u5df2\u7ecf\u88ab\u8be5LiveData\u6301\u6709\uff0c\u4e14\u8be5ObserverWrapper\u662fLifecycleBoundObserver\u5bf9\u8c61\uff0c\u8bf4\u660e\u8be5Observer\u5df2\u7ecf\u88abLifecycle\u89c2\u5bdf\uff0c\u518d\u88abForever\u89c2\u5bdf\uff0c\u5219\u76f4\u63a5\u629b\u51fa\u5f02\u5e38\u3002\n        throw new IllegalArgumentException(\"Cannot add the same observer\"\n                + \" with different lifecycles\");\n    }\n    if (existing != null) {\n        \/\/ \u8be5Observer\u5bf9\u8c61\u5df2\u7ecf\u88ab\u8be5LiveData\u6301\u6709\uff0c\u4e14\u8be5ObserverWrapper\u662f\u975eLifecycleBoundObserver\u5bf9\u8c61\uff0c\u8bf4\u660e\u8be5Observer\u5df2\u7ecf\u88abobserve()\u89c2\u5bdf\uff0c\u518d\u88abForever\u89c2\u5bdf\uff0c\u5219\u76f4\u63a5\u8fd4\u56de\u3002\n        return;\n    }\n    \/\/ \u7acb\u5373\u901a\u77e5\u6d3b\u8dc3\u72b6\u6001\u4e3a\uff1a\u6d3b\u8dc3\u7684\u3002\n    wrapper.activeStateChanged(true);\n}\n<\/code><\/pre>\n
                  observeForever()<\/code>\u65b9\u6cd5\uff0c\u5c31\u662f\u628a\u6211\u4eec\u7684Observer<\/code>\u5bf9\u8c61\u5305\u88c5\u6210AlwaysActiveObserver<\/code>\u540e\u5b58\u5165mObservers<\/code>\u4e2d\uff0c\u5e76\u4f1a\u7acb\u5373\u901a\u77e5ObserverWrapper<\/code>\u6d3b\u8dc3\u72b6\u6001\u6539\u53d8<\/strong>\u4e3a\u6d3b\u8dc3<\/strong>\u7684\u3002<\/p>\n
                  \n  \u8bf4\u660e\uff1a<\/p>\n
                    \n
                  1. observeForever()<\/code>\u65b9\u6cd5\uff0c\u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b<\/strong>\u8c03\u7528\u3002<\/li>\n
                  2. \u540c\u4e00\u4e2aLiveData<\/code>\uff0c\u65e0\u6cd5<\/strong>\u6dfb\u52a0\u5177\u6709\u4e0d\u540c\u7684<\/strong>Lifecycle<\/code>\u7684\u540c\u4e00\u4e2a<\/strong>Observer<\/code>\u3002<\/li>\n<\/ol>\n<\/blockquote>\n
                    \u63a5\u4e0b\u6765\uff0c\u6211\u4eec\u5148\u770b\u4e00\u4e0bAlwaysActiveObserver<\/code>\u7c7b\u3002<\/p>\n
                    AlwaysActiveObserver\u7c7b<\/strong><\/p>\n
                    private class AlwaysActiveObserver extends ObserverWrapper {\n\n    AlwaysActiveObserver(Observer<? super T> observer) {\n        super(observer);\n    }\n\n    \/\/ \u6b64\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u662f\u5426\u5e94\u8be5\u5904\u4e8e\u6d3b\u8dc3\u72b6\u6001\u3002\n    @Override\n    boolean shouldBeActive() {\n        \/\/ \u59cb\u7ec8\u5904\u4e8e\u6d3b\u8dc3\u72b6\u6001\uff0c\u6b64\u65b9\u6cd5\u53ea\u5728shouldBeActive()\u65b9\u6cd5\u5185\u8c03\u7528\u3002\n        return true;\n    }\n}\n<\/code><\/pre>\n
                    AlwaysActiveObserver<\/code>\u7c7b\uff0c\u662fObserverWrapper<\/code>\u5b50\u7c7b\uff0c\u5e76\u8986\u76d6\u4e86shouldBeActive()<\/code>\u65b9\u6cd5\u8ba9\u5176\u59cb\u7ec8\u5904\u4e8e\u6d3b\u8dc3\u72b6\u6001<\/strong>\u3002<\/p>\n
                    \u5c0f\u7ed3<\/h4>\n
                    \n  \u4ee3\u7801\u6d41\u7a0b\uff1a<\/p>\n
                      \n
                    1. LiveData<\/code>\u7684observeForever(observer)<\/code>\u65b9\u6cd5\uff0c\u5c06\u53c2\u6570observer<\/code>\u5305\u88c5\u6210AlwaysActiveObserver<\/code>\u540e\u6dfb\u52a0\u5230mObservers<\/code>\uff0c\u5e76\u4f1a\u7acb\u5373\u901a\u77e5ObserverWrapper<\/code>\u7684activeStateChanged()<\/code>\u65b9\u6cd5\u4e3a\u6d3b\u8dc3<\/strong>\u7684\u3002<\/li>\n
                    2. ObserverWrapper<\/code>\u7684activeStateChanged()<\/code>\u65b9\u6cd5\uff0c\u76f8\u5173\u4ecb\u7ecd\u53ca\u540e\u9762\u7684\u6d41\u7a0b\uff0c\u8bf7\u770b\u4e0a\u9762\u7684\uff1aobserve()-\u5c0f\u7ed3-\u4ee3\u7801\u6d41\u7a0b-\u6d41\u7a0b3<\/strong>\u3002<\/li>\n<\/ol>\n
                        LiveData<\/code>\u7684observeForever(observer)<\/code>\u65b9\u6cd5\u6ce8\u91ca\uff1a<\/p>\n
                        \n
                      1. \u5c06\u7ed9\u5b9a\u7684observer<\/code>\u6dfb\u52a0\u5230\u89c2\u5bdf\u8005\u5217\u8868\u4e2d\u3002\u8fd9\u4e2a\u8c03\u7528\u7c7b\u4f3c\u4e8e\u5e26\u6709\u4e00\u4e2a\u59cb\u7ec8\u5904\u4e8e\u6d3b\u8dc3\u72b6\u6001<\/strong>\u7684LifecycleOwner<\/code>\u7684observe(LifecycleOwner, Observer)<\/code>\u3002\u8fd9\u610f\u5473\u7740\u7ed9\u5b9a\u7684observer<\/code>\u5c06\u63a5\u6536\u6240\u6709\u4e8b\u4ef6\uff0c\u5e76\u4e14\u6c38\u8fdc\u4e0d\u4f1a\u88ab\u81ea\u52a8\u5220\u9664<\/strong>\u3002\u4f60\u5e94\u8be5\u624b\u52a8\u8c03\u7528removeObserver(Observer)<\/code>\u6765\u505c\u6b62\u89c2\u5bdf\u8fd9\u4e2aLiveData<\/code>\u3002\u867d\u7136LiveData<\/code>\u6709\u8fd9\u6837\u4e00\u4e2a\u89c2\u5bdf\u8005\uff0c\u4f46\u5b83\u5c06\u88ab\u8ba4\u4e3a\u662f\u6d3b\u8dc3<\/strong>\u7684\u3002<\/p>\n<\/li>\n
                      2. \u5982\u679cobserver<\/code>\u5df2\u7ecf\u6dfb\u52a0\u4e86\u4e00\u4e2aowner<\/code>\u5230\u8fd9\u4e2aLiveData<\/code>\uff0c LiveData<\/code>\u629b\u51fa\u4e00\u4e2aIllegalArgumentException<\/code>\u3002<\/p>\n<\/li>\n<\/ol>\n<\/blockquote>\n
                        \u8bbe\u7f6e\u503c<\/h2>\n
                        setValue()<\/h3>\n
                        @MainThread\nprotected void setValue(T value) {\n    \/\/ \u65ad\u8a00\u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b\u8c03\u7528\uff0c\u5426\u5219\u629b\u5f02\u5e38\u3002\n    assertMainThread(\"setValue\");\n    \/\/ \u5f53\u524dLiveData\u6570\u636e\u7684\u7248\u672c\u53f7\uff0c\u6bcf\u6b21\u6709\u65b0\u503c\u7248\u672c\u90fd\u4f1a+1\uff0c\u7528\u4e8e\u548c\u89c2\u5bdf\u8005\u5305\u88c5\u8005\u7684\u7248\u672c\u53f7\u8fdb\u884c\u6bd4\u8f83\uff0c\u5982\u679c\u89c2\u5bdf\u8005\u5305\u88c5\u8005\u7684\u7248\u672c\u53f7\u5c0f\u4e8e\u6b64\u503c\uff0c\u5219\u8fdb\u884c\u901a\u77e5\u66f4\u65b0\u3002\n    mVersion++;\n    \/\/ \u8bb0\u5f55\u9700\u8981\u5206\u53d1\u7684\u503c\n    mData = value;\n    \/\/ \u8fdb\u884c\u5206\u53d1\u503c\uff0c\u4f20null\u4ee3\u8868\u8003\u8651\u5206\u53d1\u7ed9\u6240\u6709\u7684\u89c2\u5bdf\u8005\u5305\u88c5\u8005\u3002\n    dispatchingValue(null);\n}\n<\/code><\/pre>\n
                        setValue()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u8bbe\u7f6e\u503c\u65b9\u6cd5\uff0c\u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b<\/strong>\u8c03\u7528\uff0c\u5185\u90e8\u4f1a\u5347\u7ea7\u7248\u672c\u53f7<\/strong>\u4ee5\u53ca\u66f4\u65b0\u6700\u65b0\u7684\u6570\u636e<\/strong>\uff0c\u5e76\u4e14\u4f1a\u901a\u77e5\u6240\u6709\u7684\u89c2\u5bdf\u8005<\/strong>\u5206\u53d1\u6570\u636e\u3002<\/p>\n
                        \n  LiveData<\/code>\u7684setValue(value)<\/code>\u65b9\u6cd5\u6ce8\u91ca\uff1a<\/p>\n
                          \n
                        1. \u8bbe\u7f6e\u503c<\/strong>\u3002\u5982\u679c\u6709\u6d3b\u8dc3<\/strong>\u7684\u89c2\u5bdf\u8005\uff0c\u5219\u5c06\u503c\u5206\u53d1\u7ed9\u4ed6\u4eec\u3002<\/li>\n
                        2. \u6b64\u65b9\u6cd5\u5fc5\u987b\u4ece\u4e3b\u7ebf\u7a0b<\/strong>\u8c03\u7528\u3002\u5982\u679c\u4f60\u9700\u8981\u4ece\u540e\u53f0\u7ebf\u7a0b<\/strong>\u8bbe\u7f6e\u4e00\u4e2a\u503c\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528postValue(Object)<\/code>\u3002<\/li>\n<\/ol>\n<\/blockquote>\n
                          postValue()<\/h3>\n
                          protected void postValue(T value) {\n    \/\/ \u662f\u5426\u8981\u53d1\u9001\u4efb\u52a1\n    boolean postTask;\n    \/\/ \u52a0synchronized\uff0c\u9632\u6b62\u5e76\u53d1\uff0c\u4fdd\u8bc1\u7ebf\u7a0b\u5b89\u5168\u3002\n    synchronized (mDataLock) {\n        \/\/ \u662f\u5426\u8981\u53d1\u9001\uff0c\u5982\u679cmPendingData != NOT_SET\uff0c\u5373\u4e0a\u4e00\u6b21\u7684post\u8fd8\u6ca1\u6709\u6267\u884c\uff0c\u518d\u53d1\u9001\u65b0\u503c\uff0c\u5219\u4e0d\u518d\u53d1\u9001\u3002\n        postTask = mPendingData == NOT_SET;\n        \/\/ \u8bb0\u5f55\u8981\u5f85\u5904\u7406\u7684\u6570\u636e\n        mPendingData = value;\n    }\n    if (!postTask) {\n        \/\/ \u4e0d\u53d1\u9001\uff0c\u76f4\u63a5\u8fd4\u56de\u3002\n        return;\n    }\n    \/\/ \u4f7f\u7528Handler\uff0cpost\u5230\u4e3b\u7ebf\u7a0b\uff0c\u8bbe\u7f6e\u503c\u3002\n    ArchTaskExecutor.getInstance().postToMainThread(mPostValueRunnable);\n}\n<\/code><\/pre>\n
                          private final Runnable mPostValueRunnable = new Runnable() {\n    @SuppressWarnings(\"unchecked\")\n    @Override\n    public void run() {\n        \/\/ \u8bb0\u5f55\u65b0\u503c\uff0c\u9632\u6b62mPendingData\u66f4\u6539\n        Object newValue;\n        \/\/ \u52a0synchronized\uff0c\u9632\u6b62\u5e76\u53d1\uff0c\u4fdd\u8bc1\u7ebf\u7a0b\u5b89\u5168\u3002\n        synchronized (mDataLock) {\n            \/\/ \u8bb0\u5f55\u65b0\u503c\n            newValue = mPendingData;\n            \/\/ mPendingData\u91cd\u7f6e\uff0c\u6807\u8bb0\u6267\u884c\u5b8c\u6210\u3002\n            mPendingData = NOT_SET;\n        }\n        \/\/ \u8c03\u7528setValue\uff0c\u8bbe\u7f6e\u65b0\u503c\u3002\n        setValue((T) newValue);\n    }\n};\n<\/code><\/pre>\n
                          postValue()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u8bbe\u7f6e\u503c\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u4efb\u4f55\u7ebf\u7a0b<\/strong>\u8c03\u7528\uff0c\u5185\u90e8\u4f7f\u7528Handler<\/code>\u7684post()<\/code>\u4f7f\u5176\u5728\u4e3b\u7ebf\u7a0b<\/strong>\u8bbe\u7f6e\u503c\uff0c\u8bbe\u7f6e\u503c\u662f\u8c03\u7528\u4e86\u4e0a\u9762setValue()<\/code>\u3002<\/p>\n
                          \n  LiveData<\/code>\u7684postValue(value)<\/code>\u65b9\u6cd5\u6ce8\u91ca\uff1a<\/p>\n
                            \n
                          1. \u5c06\u4efb\u52a1\u53d1\u9001\u5230\u4e3b\u7ebf\u7a0b<\/strong>\u4ee5\u8bbe\u7f6e\u7ed9\u5b9a\u503c\u3002\u6240\u4ee5\u5982\u679c\u4f60\u5728\u4e3b\u7ebf\u7a0b<\/strong>\u4e2d\u6267\u884c\u4e86\u4e0b\u9762\u7684\u4ee3\u7801\uff1a\n
                              liveData.postValue(\"a\");<\/code>
                            \n   liveData.setValue(\"b\");<\/code><\/p>\n
                              \u9996\u5148\u8bbe\u7f6e\u503c”b”\uff0c\u7136\u540e\u4e3b\u7ebf\u7a0b<\/strong>\u5c06\u7528\u503c”a”\u8986\u76d6\u5b83\u3002<\/p>\n<\/li>\n
                          2. \n
                            \u5982\u679c\u5728\u4e3b\u7ebf\u7a0b<\/strong>\u6267\u884c\u63d0\u4ea4\u7684\u4efb\u52a1\u4e4b\u524d\u591a\u6b21\u8c03\u7528<\/strong>\u6b64\u65b9\u6cd5\uff0c\u5219\u53ea\u4f1a\u5206\u53d1\u6700\u540e\u4e00\u4e2a\u503c<\/strong>\u3002<\/p>\n<\/li>\n<\/ol>\n<\/blockquote>\n
                            \u83b7\u53d6\u503c<\/h2>\n
                            getValue()<\/h3>\n
                            public T getValue() {\n    Object data = mData;\n    if (data != NOT_SET) {\n        return (T) data;\n    }\n    return null;\n}\n<\/code><\/pre>\n
                            getValue()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u83b7\u53d6\u503c\u65b9\u6cd5\uff0c\u5982\u679c\u5f53\u524d\u6709\u8bbe\u7f6e\u8fc7\u503c\uff08LiveData(value)<\/code>\u3001setValue(value)<\/code>\u3001postValue(value)<\/code> \uff09\u5219\u8fd4\u56de\u6b64\u503c<\/strong>\uff0c\u5426\u5219\u8fd4\u56denull<\/code>\u3002<\/p>\n
                            \n  LiveData<\/code>\u7684getValue()<\/code>\u65b9\u6cd5\u6ce8\u91ca\uff1a<\/p>\n
                              \n
                            1. \u8fd4\u56de\u5f53\u524d\u503c<\/strong>\u3002<\/li>\n
                            2. \u8bf7\u6ce8\u610f\uff0c\u5728\u540e\u53f0\u7ebf\u7a0b<\/strong>\u4e2d\u8c03\u7528\u6b64\u65b9\u6cd5\u5e76\u4e0d\u80fd\u4fdd\u8bc1\u5c06\u63a5\u6536\u5230\u6700\u65b0\u8bbe\u7f6e\u7684\u503c\u3002<\/li>\n
                            3. \u8fd4\u56de\uff1a\u5f53\u524d\u503c<\/strong>\uff0c\u5982\u679cisInitialized()<\/code>\u4e3afalse<\/code>\u5219\u8fd4\u56denull<\/code>\u3002<\/li>\n<\/ol>\n<\/blockquote>\n
                              \u79fb\u9664\u76d1\u542c<\/h2>\n
                              removeObserver()<\/h3>\n
                              @MainThread\npublic void removeObserver(@NonNull final Observer<? super T> observer) {\n    \/\/ \u65ad\u8a00\u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b\u8c03\u7528\uff0c\u5426\u5219\u629b\u5f02\u5e38\u3002\n    assertMainThread(\"removeObserver\");\n    \/\/ \u5c06observer\u4ecemObservers\u4e2d\u79fb\u9664\n    ObserverWrapper removed = mObservers.remove(observer);\n    if (removed == null) {\n        \/\/ removed\u4e3a\u7a7a\uff0c\u5219\u4ee3\u8868observer\u5c31\u6ca1\u6709\u88abmObservers\u6dfb\u52a0\uff0c\u76f4\u63a5\u8fd4\u56de\u3002\n        return;\n    }\n    \/\/ \u88ab\u79fb\u9664\u7684\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u5206\u79bbObserver\uff0c\u4e0d\u518d\u89c2\u5bdfObserverWrapper\u3002\n    removed.detachObserver();\n    \/\/ \u88ab\u79fb\u9664\u7684\u89c2\u5bdf\u8005\u5305\u88c5\u8005\uff0c\u901a\u77e5\u6d3b\u8dc3\u72b6\u6001\u6539\u4e3a\uff1a\u975e\u6d3b\u8dc3\u7684\u3002 \n    removed.activeStateChanged(false);\n}\n<\/code><\/pre>\n
                              removeObserver(observer)<\/code>\u65b9\u6cd5\uff0c\u4e3a\u4ece\u89c2\u5bdf\u8005\u5217\u8868<\/strong>\u4e2d\u79fb\u9664<\/strong>\u7ed9\u5b9a\u7684observer<\/code>\uff0c\u6b64\u65b9\u6cd5\u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b<\/strong>\u6267\u884c\uff0c\u5e76\u4e14\u4f1a\u5206\u79bb<\/strong>Observer<\/code>\u548c\u901a\u77e5\u6d3b\u8dc3\u72b6\u6001\u6539\u4e3a\u975e\u6d3b\u8dc3\u7684<\/strong>\u3002<\/p>\n
                              removeObservers()<\/h3>\n
                              @SuppressWarnings(\"WeakerAccess\")\n@MainThread\npublic void removeObservers(@NonNull final LifecycleOwner owner) {\n    \/\/ \u65ad\u8a00\u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b\u8c03\u7528\uff0c\u5426\u5219\u629b\u5f02\u5e38\u3002\n    assertMainThread(\"removeObservers\");\n    for (Map.Entry<Observer<? super T>, ObserverWrapper> entry : mObservers) {\n        if (entry.getValue().isAttachedTo(owner)) {\n            \/\/ \u53ea\u6709\u6240\u5c5e\u4e8eLifecycleOwner\u7684\u624d\u4f1a\u79fb\u9664\uff0c\u5982observeForever\u6dfb\u52a0\u7684\u4e0d\u4f1a\u79fb\u9664\u3002\n            removeObserver(entry.getKey());\n        }\n    }\n}\n<\/code><\/pre>\n
                              removeObservers(owner)<\/code>\u65b9\u6cd5\uff0c\u4e3a\u79fb\u9664<\/strong>\u4e0e\u7ed9\u5b9aLifecycleOwner<\/code>\u7ed1\u5b9a\u7684\u6240\u6709<\/strong>Observer<\/code>\uff08\u5982\uff1aobserveForever()<\/code>\u6dfb\u52a0\u7684\u6c38\u8fdc\u4e0d\u4f1a<\/strong>\u79fb\u9664\uff09\uff0c\u6b64\u65b9\u6cd5\u53ea\u80fd\u5728\u4e3b\u7ebf\u7a0b<\/strong>\u6267\u884c\uff0c\u5e76\u4e14\u6700\u7ec8\u4f1a\u8c03\u7528\u4e0a\u9762\u7684removeObserver(observer)<\/code>\u65b9\u6cd5\u8fdb\u884c\u5355\u4e2a\u79fb\u9664\u3002<\/p>\n
                              \u662f\u5426<\/h2>\n
                              isInitialized()<\/h3>\n
                              public boolean isInitialized() {\n    return mData != NOT_SET;\n}\n<\/code><\/pre>\n
                              isInitialized()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u6b64LiveData<\/code>\u662f\u5426\u521d\u59cb\u5316<\/strong>\u3002<\/p>\n
                              \n  LiveData<\/code>\u7684isInitialized()<\/code>\u65b9\u6cd5\u6ce8\u91ca\uff1a<\/p>\n
                                \n
                              1. \u8fd4\u56de<\/strong>\u662f\u5426\u5728\u6b64LiveData<\/code>\u4e0a\u8bbe\u7f6e\u4e86\u663e\u5f0f\u503c<\/strong>\u3002\u5982\u679c\u8fd4\u56detrue<\/code>\uff0c\u5219\u53ef\u4ee5\u4ecegetValue()<\/code>\u83b7\u53d6\u5f53\u524d\u503c\u3002<\/li>\n
                              2. \u8bf7\u6ce8\u610f\uff0c\u5373\u4f7f\u6b63\u5728\u5904\u7406\u5bf9postValue(Object)<\/code>\u7684\u8c03\u7528\uff0c\u5728\u540e\u53f0\u7ebf\u7a0b<\/strong>\u4e0a\u8c03\u7528\u6b64\u65b9\u6cd5\u4ecd\u53ef\u80fd\u5bfc\u81f4\u6b64\u65b9\u6cd5\u8fd4\u56defalse<\/code>\u3002<\/li>\n
                              3. \u8fd4\u56de\uff1a\u662f\u5426\u5728\u6b64LiveData<\/code>\u4e0a\u8bbe\u7f6e\u4e86\u663e\u5f0f\u503c<\/strong>\u3002<\/li>\n<\/ol>\n<\/blockquote>\n
                                hasObservers()<\/h3>\n
                                public boolean hasObservers() {\n    return mObservers.size() > 0;\n}\n<\/code><\/pre>\n
                                hasObservers()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u6b64LiveData<\/code>\u662f\u5426\u6709\u89c2\u5bdf\u8005<\/strong>\u3002<\/p>\n
                                hasActiveObservers()<\/h3>\n
                                public boolean hasActiveObservers() {\n    return mActiveCount > 0;\n}\n<\/code><\/pre>\n
                                hasActiveObservers()<\/code>\u65b9\u6cd5\uff0c\u4e3a\u6b64LiveData<\/code>\u662f\u5426\u6709\u6d3b\u8dc3\u7684\u89c2\u5bdf\u8005<\/strong>\u3002<\/p>\n
                                \u603b\u7ed3<\/h1>\n
                                \u4ee5\u4e0a\u5c31\u662f\u5168\u9762\u7684Jetpack-LiveData<\/code>\u6e90\u7801\u4e86\uff01\u6b22\u8fce\u5927\u5bb6\u70b9\u8d5e\u3001\u6536\u85cf<\/strong>\uff0c\u4ee5\u65b9\u4fbf\u60a8\u540e\u7eed\u67e5\u770b\uff0c\u4e4b\u540e\u4f1a\u51faJetpack<\/code>\u5176\u5b83\u6e90\u7801\u7cfb\u5217\uff0c\u8bf7\u53ca\u65f6\u5173\u6ce8\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
                                LiveData\u6e90\u7801\u89e3\u6790 \u6e90\u7801\u7248\u672c\uff1a * \u6e90\u7801\u7248\u672c\uff1a2.8.7 * \u66f4\u65b0\u65f6\u95f4\uff1a2025-3\u6708 * \u9700\u4f1a\u4f7f\u7528\uff1aL […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_lmt_disableupdate":"","_lmt_disable":"","_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[18,10],"tags":[22,23,20],"class_list":["post-71","post","type-post","status-publish","format-standard","hentry","category-source-jetpack","category-source","tag-jetpack","tag-livedata","tag-20"],"modified_by":"admin","jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"http:\/\/www.devblog.cn\/index.php?rest_route=\/wp\/v2\/posts\/71","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.devblog.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.devblog.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.devblog.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.devblog.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=71"}],"version-history":[{"count":9,"href":"http:\/\/www.devblog.cn\/index.php?rest_route=\/wp\/v2\/posts\/71\/revisions"}],"predecessor-version":[{"id":232,"href":"http:\/\/www.devblog.cn\/index.php?rest_route=\/wp\/v2\/posts\/71\/revisions\/232"}],"wp:attachment":[{"href":"http:\/\/www.devblog.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=71"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.devblog.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=71"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.devblog.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=71"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}