1 用法

（1）定義廣播接收者

 public class MyBroadcastReceiver extends BroadcastReceiver {
      @Override
      public void onReceive(Context context, Intent intent) {
          //TODO  
     }
 }

（2）註冊廣播

1 靜態註冊

<receiver android:name=".MyBroadcastReceiver" >
    <intent-filter>
        <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
    </intent-filter>
    <intent-filter>
        <action android:name="android.intent.action.BOOT_COMPLETED" />
    </intent-filter>
</receiver>

2 動態註冊

IntentFilter intentFilter = new IntentFilter();
 intentFilter.addAction(BROADCAST_ACTION);
 registerReceiver(mBroadcastReceiver, intentFilter);

（3）傳送廣播

Intent intent = new Intent();
intent.setAction(BROADCAST_ACTION);
intent.putExtra("name", "qqyumidi");
sendBroadcast(intent);

2 原始碼分析

1 ContextWrapper

 @Override
    public Intent registerReceiver(
        BroadcastReceiver receiver, IntentFilter filter) {
        return mBase.registerReceiver(receiver, filter);
    }

mBase是contextImpl，說過無數次了。

2 ContextImpl

@Override
    public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
            String broadcastPermission, Handler scheduler) {
        return registerReceiverInternal(receiver, getUserId(),
                filter, broadcastPermission, scheduler, getOuterContext());
    }
 

private Intent registerReceiverInternal(BroadcastReceiver receiver, int userId,
            IntentFilter filter, String broadcastPermission,
            Handler scheduler, Context context) {
        IIntentReceiver rd = null;
        if (receiver != null) {
            if (mPackageInfo != null && context != null) {
                if (scheduler == null) {
                    scheduler = mMainThread.getHandler();
                }
                rd = mPackageInfo.getReceiverDispatcher(
                    receiver, context, scheduler,
                    mMainThread.getInstrumentation(), true);
            } else {
                if (scheduler == null) {
                    scheduler = mMainThread.getHandler();
                }
                rd = new LoadedApk.ReceiverDispatcher(
                        receiver, context, scheduler, null, true).getIIntentReceiver();
            }
        }
        try {
            return ActivityManagerNative.getDefault().registerReceiver(
                    mMainThread.getApplicationThread(), mBasePackageName,
                    rd, filter, broadcastPermission, userId);
        } catch (RemoteException e) {
            return null;
        }
    }

因為註冊廣播是一個程序間通訊的過程，所以不能直接只用BroadcastReceiver。mPackageInfo.getReceiverDispatcher將broadcast轉化為一個binder，這個過程和service的

mPackageInfo.getServiceDispatcher型別。mPackageInfo是LoadedApk例項，下面看看getReceiverDispatcher

3 LoadedApk

public IIntentReceiver getReceiverDispatcher(BroadcastReceiver r,
            Context context, Handler handler,
            Instrumentation instrumentation, boolean registered) {
        synchronized (mReceivers) {
            LoadedApk.ReceiverDispatcher rd = null;
            ArrayMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher> map = null;
            if (registered) {
                map = mReceivers.get(context);
                if (map != null) {
                    rd = map.get(r);
                }
            }
       ......
                rd = new ReceiverDispatcher(r, context, handler,
                        instrumentation, registered);
            ......
            return rd.getIIntentReceiver();
        }
    }

這裡涉及到LoadedApk，ReceiverDispatcher，

private final ArrayMap<Context, ArrayMap<BroadcastReceiver, ReceiverDispatcher>> mReceivers
        = new ArrayMap<Context, ArrayMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher>>();

rd是一個ReceiverDispatcher例項，他呼叫了自己的getIIntentReceiver方法

 IIntentReceiver getIIntentReceiver() {
            return mIIntentReceiver;
        }

mIIntentReceiver是一個binder，下面就來看看怎麼把broadcastReceiver轉化為binder的

4  ReceiverDispatcher

ReceiverDispatcher(BroadcastReceiver receiver, Context context,
                Handler activityThread, Instrumentation instrumentation,
                boolean registered) {
            if (activityThread == null) {
                throw new NullPointerException("Handler must not be null");
            }

            mIIntentReceiver = new InnerReceiver(this, !registered);
            mReceiver = receiver;
            mContext = context;
            mActivityThread = activityThread;
            mInstrumentation = instrumentation;
            mRegistered = registered;
            mLocation = new IntentReceiverLeaked(null);
            mLocation.fillInStackTrace();
        }

ReceiverDispatcher例項化時建立了InnerReceiver，InnerReceiver就是一個binder，這裡就將broadcastReceiver“轉化“為binder了，其實這個過程和service轉化為binder一模一樣，可以結合service來比較。

5 InnerReceiver

  final static class InnerReceiver extends IIntentReceiver.Stub {
            final WeakReference<LoadedApk.ReceiverDispatcher> mDispatcher;
            final LoadedApk.ReceiverDispatcher mStrongRef;

            InnerReceiver(LoadedApk.ReceiverDispatcher rd, boolean strong) {
                mDispatcher = new WeakReference<LoadedApk.ReceiverDispatcher>(rd);
                mStrongRef = strong ? rd : null;
            }
            public void performReceive(Intent intent, int resultCode, String data,
                    Bundle extras, boolean ordered, boolean sticky, int sendingUser) {
              ......
            }
        }

6  ActivityManagerProxy(ActivityManager內部類)

回到第2步，接著執行了ActivityManagerNative.getDefault().registerReceiver，什麼不用說了，大家都懂，直接上程式碼。