Broadcast的使用

Android广播机制采用观察者模式

接收者

BroadcastReceiver

该类为广播接收器类，示例代码为：

public class MyBroadcastReceiver extends BroadcastReceiver {
    public static final String TAG = "MyBroadcastReceiver";
    @Override
    public void onReceive(Context context, Intent intent) {
        Log.i(TAG,"onReceive");
    }
}

当发送者发送广播时，onReceive方法会被触发执行

广播监听注册

静态注册

<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>

action android:name的值指定的是触发条件：

android.net.conn.CONNECTIVITY_CHANGE

指的是网络改变

android.intent.action.BOOT_COMPLETED

指的是系统启动

动态注册

public class MainActivity extends Activity {
    public static final String BROADCAST_ACTION = "grooters.github.io";
    private BroadcastReceiver mBroadcastReceiver;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mBroadcastReceiver = new MyBroadcastReceiver();
        IntentFilter intentFilter = new IntentFilter();
        //添加触发条件
        intentFilter.addAction(BROADCAST_ACTION);
        registerReceiver(mBroadcastReceiver, intentFilter);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        //注销该监听器
        unregisterReceiver(mBroadcastReceiver);
    }
}

当发送者发送的广播的Action为grooters.github.io时便会触发该监听器

发送者

Intent intent=new Intent();
intent.setAction(BROADCAST_ACTION);
//可在监听方法onReceiver的intent参数中取出数据
intent.putExtra("data","Hello");
sendBroadcast(intent);

广播类型

普通广播

系统广播

提供多个已存在的系统动作Action，如开机自启，网络改变，电量不足

有序广播

有顺序地接收不同的广播，顺序取决于priority的值，越大就越前

<intent-filter android:priority="1">

本地广播

只有本app能接收到该广播

//接收者
LocalBroadcastManager localBroadcastManager = LocalBroadcastManager.getInstance(this);
localBroadcastManager.registerReceiver(mBroadcastReceiver, intentFilter);
localBroadcastManager.unregisterReceiver(mBroadcastReceiver);

//发送者
Intent intent = new Intent();
intent.setAction(BROADCAST_ACTION);
intent.putExtra("data", "Hello");
localBroadcastManager.sendBroadcast(intent);

onReceive中的Context

镜头注册

context 具体指的是 ReceiverRestrictedContext

动态注册

context 具体指的是 Activity Context

本地广播

context 具体指的是 Application Context