使用Android RemoteCallbackList简化远端接口跨进程回调

RemoteCallbackList

负责维护远程接口列表的繁琐工作，通常用于执行从Service到其客户端的回调

跟踪一组已注册的IInterface回调，注意通过唯一的IBinder来识别它们（通过调用IInterface#asBinder.)
给每个注册的接口附加一个IBinder.DeathRecipient，这样，如果它的进程消失，就可以从列表中清理.
执行对底层接口列表的锁定，以处理多线程传入的调用，并以线程安全的方式迭代该列表的快照，而不持有其锁定。

如何使用?

要使用这个类，只需与你的服务一起创建一个实例，并调用它的register(E)和unregister(E)方法作为客户端注册和取消注册服务。要回调到注册的客户端，请使用 beginBroadcast()、getBroadcastItem(int)和finishBroadcast()。
如果一个已注册的回调进程消失了，这个类将负责自动将其从列表中删除。
如果你想在这种情况下做额外的工作，你可以创建一个子类来实现onCallbackDied(E)方法。

源码分析:

public class RemoteCallbackList<E extends IInterface> {private static final String TAG = "RemoteCallbackList";/*package*/ ArrayMap<IBinder, Callback> mCallbacks= new ArrayMap<IBinder, Callback>();private Object[] mActiveBroadcast;private int mBroadcastCount = -1;private boolean mKilled = false;private StringBuilder mRecentCallers;private final class Callback implements IBinder.DeathRecipient {final E mCallback;final Object mCookie;Callback(E callback, Object cookie) {mCallback = callback;mCookie = cookie;}//客户端回调死亡通知public void binderDied() {synchronized (mCallbacks) {mCallbacks.remove(mCallback.asBinder());}//可以复写此方法来在客户端回调进程挂掉做某些事情onCallbackDied(mCallback, mCookie);}}/*** Simple version of {@link RemoteCallbackList#register(E, Object)}* that does not take a cookie object.*/public boolean register(E callback) {return register(callback, null);}/*** 在列表中添加一个新的回调。这个回调将保留在列表中，直到调用{@link #unregister}或其托管进程消失。* 这个回调已经注册了（通过检查{@link IInterface#asBinder callback.asBinder()}对象是否已经在列表中存在），* 那么它将被重用。* @param callback 添加到列表中的回调接口 不能为null** @param cookie可选择与此回调关联的附加数据。* * @return 如果添加成功则返回true ,没有被添加成功则返回false* @see #unregister* @see #kill* @see #onCallbackDied*/public boolean register(E callback, Object cookie) {synchronized (mCallbacks) {if (mKilled) {return false;}// Flag unusual case that could be caused by a leak. b/36778087logExcessiveCallbacks();//获取回调的binderIBinder binder = callback.asBinder();try {Callback cb = new Callback(callback, cookie);//将每个回调的客户端注册死亡回调binder.linkToDeath(cb, 0);//防止反复实例化,节省空间mCallbacks.put(binder, cb);return true;} catch (RemoteException e) {return false;}}}/*** 从列表删除之前添加的回调** @param callback The callback to be removed from the list.  Passing* null here will cause a NullPointerException, so you will generally want* to check for null before calling.** @return Returns true if the callback was found and unregistered.  Returns* false if the given callback was not found on the list.** @see #register*/public boolean unregister(E callback) {synchronized (mCallbacks) {Callback cb = mCallbacks.remove(callback.asBinder());if (cb != null) {cb.mCallback.asBinder().unlinkToDeath(cb, 0);return true;}return false;}}/*** 禁用此回调列表。 * 所有已注册的回调都是未注册的，并且这个列表被禁用，这样以后调用{@link #register}就会失败。 * 这应该在服务停止时使用，以防止客户端在服务停止后注册回调。** @see #register*/public void kill() {synchronized (mCallbacks) {for (int cbi=mCallbacks.size()-1; cbi>=0; cbi--) {Callback cb = mCallbacks.valueAt(cbi);cb.mCallback.asBinder().unlinkToDeath(cb, 0);}mCallbacks.clear();mKilled = true;}}/*** Old version of {@link #onCallbackDied(E, Object)} that* does not provide a cookie.*/public void onCallbackDied(E callback) {}/*** Called when the process hosting a callback in the list has gone away.* The default implementation calls {@link #onCallbackDied(E)}* for backwards compatibility.* * @param callback The callback whose process has died.  Note that, since* its process has died, you can not make any calls on to this interface.* You can, however, retrieve its IBinder and compare it with another* IBinder to see if it is the same object.* @param cookie The cookie object original provided to* {@link #register(E, Object)}.* * @see #register*/public void onCallbackDied(E callback, Object cookie) {onCallbackDied(callback);}/*** 准备调用已经注册的回调,使用getBroadcastItem()检索回调* 注意:一次只能进行一次广播** <p>一个典型的循环广播看起来是这样的。*** @return Returns the number of callbacks in the broadcast, to be used* with {@link #getBroadcastItem} to determine the range of indices you* can supply.** @see #getBroadcastItem* @see #finishBroadcast*/public int beginBroadcast() {synchronized (mCallbacks) {if (mBroadcastCount > 0) {throw new IllegalStateException("beginBroadcast() called while already in a broadcast");}final int N = mBroadcastCount = mCallbacks.size();if (N <= 0) {return 0;}Object[] active = mActiveBroadcast;if (active == null || active.length < N) {mActiveBroadcast = active = new Object[N];}for (int i=0; i<N; i++) {active[i] = mCallbacks.valueAt(i);}return N;}}/*** 调用了beginBroadcast之后,调用此方法,获取回调列表里面的子项* ** @param index Which of the registered callbacks you would like to* retrieve.  Ranges from 0 to 1-{@link #beginBroadcast}.** @return Returns the callback interface that you can call.  This will* always be non-null.** @see #beginBroadcast*/public E getBroadcastItem(int index) {return ((Callback)mActiveBroadcast[index]).mCallback;}/*** Retrieve the cookie associated with the item* returned by {@link #getBroadcastItem(int)}.* * @see #getBroadcastItem*/public Object getBroadcastCookie(int index) {return ((Callback)mActiveBroadcast[index]).mCookie;}/*** Clean up the state of a broadcast previously initiated by calling* {@link #beginBroadcast}.  This must always be called when you are done* with a broadcast.** @see #beginBroadcast*/public void finishBroadcast() {synchronized (mCallbacks) {if (mBroadcastCount < 0) {throw new IllegalStateException("finishBroadcast() called outside of a broadcast");}Object[] active = mActiveBroadcast;if (active != null) {final int N = mBroadcastCount;for (int i=0; i<N; i++) {//将活动的callback 置为nullactive[i] = null;}}mBroadcastCount = -1;}}/*** Performs {@code action} on each callback, calling* {@link #beginBroadcast()}/{@link #finishBroadcast()} before/after looping** @hide*/public void broadcast(Consumer<E> action) {int itemCount = beginBroadcast();try {for (int i = 0; i < itemCount; i++) {action.accept(getBroadcastItem(i));}} finally {finishBroadcast();}}/*** Performs {@code action} for each cookie associated with a callback, calling* {@link #beginBroadcast()}/{@link #finishBroadcast()} before/after looping** @hide*/public <C> void broadcastForEachCookie(Consumer<C> action) {int itemCount = beginBroadcast();try {for (int i = 0; i < itemCount; i++) {action.accept((C) getBroadcastCookie(i));}} finally {finishBroadcast();}}/*** 返回注册的回调数量* ** @return The size.*/public int getRegisteredCallbackCount() {synchronized (mCallbacks) {if (mKilled) {return 0;}return mCallbacks.size();}}/*** 根据索引返回已注册的回调,线程不安全,会受到unregister的影响** @param index Index of which callback registration to return, from 0 to* {@link #getRegisteredCallbackCount()} - 1.** @return Returns whatever callback is associated with this index, or null if* {@link #kill()} has been called.*/public E getRegisteredCallbackItem(int index) {synchronized (mCallbacks) {if (mKilled) {return null;}return mCallbacks.valueAt(index).mCallback;}}/*** 根据索引返回当前注册回调的cookie* @param index Index of which registration cookie to return, from 0 to* {@link #getRegisteredCallbackCount()} - 1.** @return Returns whatever cookie object is associated with this index, or null if* {@link #kill()} has been called.*/public Object getRegisteredCallbackCookie(int index) {synchronized (mCallbacks) {if (mKilled) {return null;}return mCallbacks.valueAt(index).mCookie;}}
}

具体的使用例子请参考链接.

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使用Android RemoteCallbackList简化远端接口跨进程回调

RemoteCallbackList

负责维护远程接口列表的繁琐工作，通常用于执行从Service到其客户端的回调

如何使用?

源码分析:

具体的使用例子请参考链接.

使用Android RemoteCallbackList简化远端接口跨进程回调相关推荐

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