使用

1. 自定義 BroadcastReveicer 子類

public class LocalBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context arg0, Intent intent) {
        Bitmap bitmap = intent.getParcelableExtra("bitmap");
        image.setImageBitmap(bitmap);
    }
    
} 

2. 注冊接收器

localReceiver = new LocalBroadcastReceiver();
LocalBroadcastManager.getInstance(this).registerReceiver(localReceiver, new IntentFilter(ACTION_LOCAL_SEND));

3. 發(fā)送廣播
   網(wǎng)絡(luò)請求成功

LocalBroadcastManager.getInstance(TestHttpURLConnection.this)
                            .sendBroadcast(new Intent(ACTION_LOCAL_SEND)
                            .putExtra("bitmap", bitmap));

4. 取消注冊

@Override
protected void onDestroy() {
    super.onDestroy();
    LocalBroadcastManager.getInstance(this).unregisterReceiver(localReceiver);
}

實現(xiàn)

public static LocalBroadcastManager getInstance(Context context) {
synchronized (mLock) {
    if (mInstance == null) {
        mInstance = new LocalBroadcastManager(context.getApplicationContext());
    }
    return mInstance;
}
}

private LocalBroadcastManager(Context context) {
mAppContext = context;
mHandler = new Handler(context.getMainLooper()) {

    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case MSG_EXEC_PENDING_BROADCASTS:
                executePendingBroadcasts();
                break;
            default:
                super.handleMessage(msg);
        }
    }
};
}

單例實現(xiàn)因而私有化構(gòu)造函數(shù)，基于主線程的 Looper 新建了一個 Handler，handleMessage
中會調(diào)用接收器對廣播的消息進行處理

注冊接收器

HashMap<BroadcastReceiver, ArrayList<IntentFilter>> mReceivers
        = new HashMap<BroadcastReceiver, ArrayList<IntentFilter>>();
HashMap<String, ArrayList<ReceiverRecord>> mActions
        = new HashMap<String, ArrayList<ReceiverRecord>>();

public void registerReceiver(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);
    for (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);
    }
}
} 

mReceivers 存儲廣播和過濾器信息，以BroadcastReceiver作為 key，IntentFilter鏈表作為 value。
mReceivers 是接收器和IntentFilter的對應(yīng)表，主要作用是方便在unregisterReceiver(…)取消注冊，同時作為對象鎖限制注冊接收器、發(fā)送廣播、取消接收器注冊等幾個過程的并發(fā)訪問。

mActions 以Action為 key，注冊這個Action的BroadcastReceiver鏈表為 value。mActions 的主要作用是方便在廣播發(fā)送后快速得到可以接收它的BroadcastReceiver。

發(fā)送廣播

先根據(jù)Action從mActions中取出ReceiverRecord列表，循環(huán)每個ReceiverRecord判斷 filter 和 intent 中的action、type、scheme、data、categoried 是否 match，是的話則保存到receivers列表中，發(fā)送 what 為MSG_EXEC_PENDING_BROADCASTS的消息，通過 Handler 去處理。

消息處理

private void executePendingBroadcasts() {
while (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++) {
            br.receivers.get(j).receiver.onReceive(mAppContext, br.intent);
        }
    }
}
}

mPendingBroadcasts轉(zhuǎn)換為數(shù)組BroadcastRecord，循環(huán)每個receiver，調(diào)用其onReceive函數(shù)

取消注冊

從mReceivers及mActions中移除相應(yīng)元素。