源码分析/* * Copyright (C) 2011 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the “License”); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an “AS IS” BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package android.support.v4.content;import java.util.ArrayList;import java.util.HashMap;import java.util.Set;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.content.IntentFilter;import android.net.Uri;import android.os.Handler;import android.os.Message;import android.util.Log;/** * Helper to register for and send broadcasts of Intents to local objects * within your process. This is has a number of advantages over sending * global broadcasts with {@link android.content.Context#sendBroadcast}: * <ul> * <li> You know that the data you are broadcasting won’t leave your app, so * don’t need to worry about leaking private data. * <li> It is not possible for other applications to send these broadcasts to * your app, so you don’t need to worry about having security holes they can * exploit. * <li> It is more efficient than sending a global broadcast through the * system. * </ul> */{{final IntentFilter filter;final BroadcastReceiver receiver;boolean broadcasting;ReceiverRecord(IntentFilter _filter, BroadcastReceiver _receiver) {filter = _filter;receiver = _receiver;}@Overridepublic String toString() {StringBuilder builder = new StringBuilder(128);builder.append(“Receiver{“);builder.append(receiver);builder.append(” filter=”);builder.append(filter);builder.append(“}”);return builder.toString();}}{final Intent intent;final ArrayList<ReceiverRecord> receivers;BroadcastRecord(Intent _intent, ArrayList<ReceiverRecord> _receivers) {intent = _intent;receivers = _receivers;}}String TAG = “LocalBroadcastManager”;DEBUG = false;private final Context mAppContext;HashMap<BroadcastReceiver, ArrayList<IntentFilter>> mReceivers= new HashMap<BroadcastReceiver, ArrayList<IntentFilter>>();private final HashMap<String, ArrayList<ReceiverRecord>> mActions= new HashMap<String, ArrayList<ReceiverRecord>>();mPendingBroadcasts存放即将要广播的action和对应的receiverprivate final ArrayList<BroadcastRecord> mPendingBroadcasts= new ArrayList<BroadcastRecord>();MSG_EXEC_PENDING_BROADCASTS = 1;Handler mHandler;Object mLock = new Object();private static LocalBroadcastManager mInstance;LocalBroadcastManager getInstance(Context context) {synchronized (mLock) {if (mInstance == null) {mInstance = new LocalBroadcastManager(context.getApplicationContext());}return mInstance;}}private LocalBroadcastManager(Context context) {mAppContext = context;// handler是和mainLooper关联的mHandler = new Handler(context.getMainLooper()) {(Message msg) {switch (msg.what) {case MSG_EXEC_PENDING_BROADCASTS:executePendingBroadcasts();break;default:super.handleMessage(msg);}}};}/*** Register a receive for any local broadcasts that match the given IntentFilter.** @param receiver The BroadcastReceiver to handle the broadcast.* @param filter Selects the Intent broadcasts to be received.** @see #unregisterReceiver*/(BroadcastReceiver receiver, IntentFilter filter) {synchronized (mReceivers) {ReceiverRecord entry = new ReceiverRecord(filter, receiver);ArrayList<IntentFilter> filters = mReceivers.get(receiver);if (filters == null) {filters = new ArrayList<IntentFilter>(1);mReceivers.put(receiver, filters);}filters.add(filter);(int i=0; i<filter.countActions(); i++) {String action = filter.getAction(i);ArrayList<ReceiverRecord> entries = mActions.get(action);if (entries == null) {entries = new ArrayList<ReceiverRecord>(1);mActions.put(action, entries);}entries.add(entry);}}}/*** Unregister a previously registered BroadcastReceiver. <em>All</em>* filters that have been registered for this BroadcastReceiver will be* removed.** @param receiver The BroadcastReceiver to unregister.** @see #registerReceiver*/(BroadcastReceiver receiver) {synchronized (mReceivers) {// 和注册广播时相比，取消注册就是取消action和receiver的映射// 先从mReceivers里remove对应的receiver，返回的actions用于后续操作ArrayList<IntentFilter> filters = mReceivers.remove(receiver);if (filters == null) {return;}// receiver对应的action存在，则从action对应的receiver里removefor (int i=0; i<filters.size(); i++) {IntentFilter filter = filters.get(i);for (int j=0; j<filter.countActions(); j++) {String action = filter.getAction(j);ArrayList<ReceiverRecord> receivers = mActions.get(action);if (receivers != null) {for (int k=0; k<receivers.size(); k++) {if (receivers.get(k).receiver == receiver) {// 找到了，则从action对应的receiver列表移除receivers.remove(k);k–;}}if (receivers.size() <= 0) {// 该action没有receiver了，则将这项removemActions.remove(action);}}}}}}/*** Broadcast the given intent to all interested BroadcastReceivers. This* call is asynchronous; it returns immediately, and you will continue* executing while the receivers are run.** @param intent The Intent to broadcast; all receivers matching this*Intent will receive the broadcast.** @see #registerReceiver*/(Intent intent) {// 异步发送广播，广播接收器的onReceive在主线程执行synchronized (mReceivers) {// 取出intent的相关属性,action,type,data,categoriesfinal String action = intent.getAction();final String type = intent.resolveTypeIfNeeded(mAppContext.getContentResolver());final Uri data = intent.getData();final String scheme = intent.getScheme();final Set<String> categories = intent.getCategories();final boolean debug = DEBUG ||((intent.getFlags() & Intent.FLAG_DEBUG_LOG_RESOLUTION) != 0);if (debug) Log.v(TAG, “Resolving type ” + type + ” scheme ” + scheme+ ” of intent ” + intent);// 根据action找出其对应的所有receiverArrayList<ReceiverRecord> entries = mActions.get(intent.getAction());if (entries != null) {if (debug) Log.v(TAG, “Action list: ” + entries);// 遍历该action对应的receiversArrayList<ReceiverRecord> receivers = null;for (int i=0; i<entries.size(); i++) {ReceiverRecord receiver = entries.get(i);if (debug) Log.v(TAG, “Matching against filter ” + receiver.filter);if (receiver.broadcasting) {// broadcasting是一个临时标志，用于防止重复加入if (debug) {Log.v(TAG, ” Filter’s target already added”);}continue;}// 对每个receiver和发送的intent做匹配，匹配过程在这里暂不展开int match = receiver.filter.match(action, type, scheme, data,categories, “LocalBroadcastManager”);if (match >= 0) {// 要广播的intent和该receiver的过滤器匹配if (debug) Log.v(TAG, ” Filter matched! match=0x” +Integer.toHexString(match));if (receivers == null) {receivers = new ArrayList<ReceiverRecord>();}// 先放入数组，并置标志位receivers.add(receiver);receiver.broadcasting = true;} else {if (debug) {// debug信息String reason;switch (match) {case IntentFilter.NO_MATCH_ACTION: reason = “action”; break;case IntentFilter.NO_MATCH_CATEGORY: reason = “category”; break;case IntentFilter.NO_MATCH_DATA: reason = “data”; break;case IntentFilter.NO_MATCH_TYPE: reason = “type”; break;default: reason = “unknown reason”; break;}Log.v(TAG, ” Filter did not match: ” + reason);}}}if (receivers != null) {// 找到了该intent对应的receiverfor (int i=0; i<receivers.size(); i++) {// 先清除标志receivers.get(i).broadcasting = false;}// 放入待广播容器mPendingBroadcastsmPendingBroadcasts.add(new BroadcastRecord(intent, receivers));if (!mHandler.hasMessages(MSG_EXEC_PENDING_BROADCASTS)) {//抛到主线程执行，，executePendingBroadcastsmHandler.sendEmptyMessage(MSG_EXEC_PENDING_BROADCASTS);}return true;}}}return false;}/*** Like {@link #sendBroadcast(Intent)}, but if there are any receivers for* the Intent this function will block and immediately dispatch them before* returning.*/(Intent intent) {if (sendBroadcast(intent)) {//同步执行，在哪个线程发送的广播，在哪个线程执行executePendingBroadcasts();}}() {// 真正发送的地方，操作的数据结构是mPendingBroadcastswhile (true) {BroadcastRecord[] brs = null;synchronized (mReceivers) {final int N = mPendingBroadcasts.size();if (N <= 0) {return;}brs = new BroadcastRecord[N];mPendingBroadcasts.toArray(brs);mPendingBroadcasts.clear();}for (int i=0; i<brs.length; i++) {BroadcastRecord br = brs[i];for (int j=0; j<br.receivers.size(); j++) {// 调用onReceivebr.receivers.get(j).receiver.onReceive(mAppContext, br.intent);}}}}}小结扩展在发送广播时，intentFilter是如何过滤出匹配的receiver的呢？
即使爬到最高的山上，一次也只能脚踏实地地迈一步。
