Android 中LocalBroadcastManager的使用方式

Android中BroadcastReceiver主要用途有

发送通知，更新UI或者数据，应用程序间相互通信，监听系统状态（比如开机，网络等）

Android中BroadcasetReceiver的注册方式

1. manifest清单文件中的全局注册

2. 按照生命周期，在Service或者Activity中使用代码注册

manifest的注册方式

<receiver android:name="com.sample.test.MyBroadcastReciever">  
            <intent-filter>  
                <action android:name="com.sample.test.ACTION_DO_SOMETHING"></action>
                <action android:name="android.intent.ACTION_WIFI_STATE_CHANGED"></action>  
            </intent-filter>  
  </receiver>

使用代码注册

SampleActivity

private  MyReceiver receiver;

@Override 
public void onStart() {
      super.onStart();  
    receiver = new MyReceiver();
    IntentFilter filter = new IntentFilter();
    filter.addAction("android.intent.action.MY_BROADCAST");
    registerReceiver(receiver, filter);
}
@Override
public void onStop(){
    super.onStop();
    unregisterReceiver(receiver);  
}

Android中发送广播的方式

普通广播：无论优先级大小，将发送给所有监听Action="com.test.sample.action"的广播,内容不可被修改，无传递性。

Intent intent = new Intent( "com.test.sample.action");
sendBroadcast(intent);

异步（黏性）广播: 当处理完之后的Intent ，依然存在，这时候registerReceiver(BroadcastReceiver, IntentFilter) 还能收到他的值，直到你把它去掉 , 无传递性 , 无法终止(abort())广播。

发这个广播需要权限<uses-permission android:name="android.permission.BROADCAST_STICKY" />

去掉是用这个方法removeStickyBroadcast(intent); 但别忘了在执行这个方法的应用里面 AndroidManifest.xml 同样要加上面的权限；

sendStickyOrderedBroadcast(intent, resultReceiver, scheduler,
       initialCode, initialData, initialExtras)

有序广播：

按照接收者的优先级顺序接收广播 , 优先级别在 intent-filter 中的 priority 中声明 ,-1000 到1000 之间 ，值越大 优先级越高 。可以终止广播意图的继续传播 ， 接收者可以篡改内容，具有传递性。

sendBroadcast(intent);

Android中的BroadcastReceiver可以用来发送信息到另一个广播，这种方式可实现程序或者进程间的通行。

上面回顾了一下Android的广播用例，总体来说安全性都不太好，因此只适用于安全性较低的数据传递，或者页面更新。

在android-support-v4.jar中引入了LocalBroadcastManager，称为局部通知管理器，这种通知的好处是安全性高，效率也高，适合局部通信，可以用来代替Handler更新UI

public class LocalServiceBroadcasterActivity extends Activity {
    static final String ACTION_STARTED = "com.example.android.supportv4.STARTED";
    static final String ACTION_UPDATE = "com.example.android.supportv4.UPDATE";
    static final String ACTION_STOPPED = "com.example.android.supportv4.STOPPED";

    LocalBroadcastManager mLocalBroadcastManager;
    BroadcastReceiver mReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        final TextView callbackData = (TextView) findViewById(R.id.callback);
        callbackData.setText("No broadcast received yet");
        mLocalBroadcastManager = LocalBroadcastManager.getInstance(this);

        IntentFilter filter = new IntentFilter();
        filter.addAction(ACTION_STARTED);
        filter.addAction(ACTION_UPDATE);
        filter.addAction(ACTION_STOPPED);
        
        mReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                if (intent.getAction().equals(ACTION_STARTED)) {
                    callbackData.setText("STARTED");
                } else if (intent.getAction().equals(ACTION_UPDATE)) {
                    callbackData.setText("Got update: " + intent.getIntExtra("value", 0));
                } else if (intent.getAction().equals(ACTION_STOPPED)) {
                    callbackData.setText("STOPPED");
                }
            }
        };
        mLocalBroadcastManager.registerReceiver(mReceiver, filter);

        
        Button button = (Button) findViewById(R.id.start);
        button.setOnClickListener(mStartListener);
        button = (Button) findViewById(R.id.stop);
        button.setOnClickListener(mStopListener);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mLocalBroadcastManager.unregisterReceiver(mReceiver);
    }

    private OnClickListener mStartListener = new OnClickListener() {
        public void onClick(View v) {
            startService(new Intent(LocalServiceBroadcasterActivity.this, LocalService.class));
        }
    };

    private OnClickListener mStopListener = new OnClickListener() {
        public void onClick(View v) {
            stopService(new Intent(LocalServiceBroadcasterActivity.this, LocalService.class));
        }
    };

    public static class LocalService extends Service {
        LocalBroadcastManager mLocalBroadcastManager;
        int mCurUpdate;

        static final int MSG_UPDATE = 1;

        Handler mHandler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                switch (msg.what) {
                case MSG_UPDATE: {
                    mCurUpdate++;
                    Intent intent = new Intent(ACTION_UPDATE);
                    intent.putExtra("value", mCurUpdate);
                    mLocalBroadcastManager.sendBroadcast(intent);
                    Message nmsg = mHandler.obtainMessage(MSG_UPDATE);
                    mHandler.sendMessageDelayed(nmsg, 1000);
                }
                    break;
                default:
                    super.handleMessage(msg);
                }
            }
        };

        @Override
        public void onCreate() {
            super.onCreate();
            mLocalBroadcastManager = LocalBroadcastManager.getInstance(this);
        }

        public int onStartCommand(Intent intent, int flags, int startId) {
            // Tell any local interested parties about the start.
            mLocalBroadcastManager.sendBroadcast(new Intent(ACTION_STARTED));

            // Prepare to do update reports.
            mHandler.removeMessages(MSG_UPDATE);
            Message msg = mHandler.obtainMessage(MSG_UPDATE);
            mHandler.sendMessageDelayed(msg, 1000);
            return ServiceCompat.START_STICKY;
        }

        @Override
        public void onDestroy() {
            super.onDestroy();

            // Tell any local interested parties about the stop.
            mLocalBroadcastManager.sendBroadcast(new Intent(ACTION_STOPPED));

            // Stop doing updates.
            mHandler.removeMessages(MSG_UPDATE);
        }

        @Override
        public IBinder onBind(Intent intent) {
            return null;
        }
    }
}