BroadCast Receiver的使用

Posted 2020-08-06 醉清风

定义

广播接收器分为标准广播和有序广播，标准广播是异步执行的广播，有序广播是同步执行的，同一时刻只有一个广播接收器会收到广播，执行结束后，广播才会继续传递。

静态注册

在androidmanifest.xml中添加<receiver>节点，并在代码中定义相应的类。在receiver字段里面可以指定priority来指定receiver的优先级，优先级高的会先接收到消息。如果不指定，后注册的receiver先接收到消息

        <receiver android:name=".BootCompleteReceiver">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            </intent-filter>
        </receiver>
    </application>
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>

public class BootCompleteReceiver extends BroadcastReceiver {
    //static registered in AndroidManifest.xml
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "Boot Complete", Toast.LENGTH_SHORT).show();
    }
}

动态注册

可以在代码中注册，这种方法比较灵活，可以自由的注册与注销，但是缺点是必须要程序启动才能收到广播。只需要创建一个BroadcastReceiver的子类并重写父类的onReceive函数就可以了。当有广播到来时，onReceive方法就会被执行。

public class MyReceiver extends BroadcastReceiver {

    public static final String ACTION = "com.wanxiang.www.learnbroadcastreceiver.intent.action.myReceiver";

case R.id.btnRegister:
                if (myReceiver == null){
                    myReceiver = new MyReceiver();
                    registerReceiver(myReceiver, new IntentFilter(MyReceiver.ACTION));
                }
                break;
            case R.id.btnUnRegister:
                if (myReceiver != null){
                    unregisterReceiver(myReceiver);
                    myReceiver =null;
                }
                break;

自定义广播

其他都同动态静态注册的broadcastreceiver一样，只是intent-filter写的是自己定义的broadcast,同样在类中也要写发送相应的broadcast(可能在一个button的click中)：

Intent intent = new Intent("com.wanxiang.www.broadcastreceiver.MY_BROADCAST");
//标准广播
sendBroadcast(intent);
//有序广播，可以被abortBroadcast()截断
sendOrderedBroadcast(intent,null)；

有序广播

发送的有序广播可以在BroadcastReceiver的onReceive函数中被截断：

sendOrderedBroadcast(i, null);

    @Override
    public void onReceive(Context context, Intent intent) {
        // TODO: This method is called when the BroadcastReceiver is receiving
        // an Intent broadcast.
        System.out.println("MyReceiver1接受到了消息");
        abortBroadcast();
    }

 

本地广播

只让broadcast在应用程序内部进行传递