Broadcast Receiver 简单应用

标签（空格分隔）： Android

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概要

Broadcast Receiver,广播接收器，是 android四大组件之一，用于监听应用发出的广播，并做出适当响应
观察者模式
全局广播：

动态注册：

简单应用：
e.g.监听网络变化

1. 先建一个内部类，继承自BroadcastReceiver,重写父类的onReceive

 class NetworkChangeReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectionManager = (ConnectivityManager)
            getSystemService(Context.CONNECTIVITY_SERVICE);
           NetworkInfo networkInfo = connectionManager.getActiveNetworkInfo();
            if (networkInfo != null && networkInfo.isAvailable()) {
               Toast.makeText(context, "network is available",
                        Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(context, "network is unavailable",
                        Toast.LENGTH_SHORT).show();
            }

2. 创建一个IntentFiler实例，添加相应的action

       
intentFilter = new IntentFilter();
intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");     

3. 创建一个自定义的Receiver实例，调用registerReceiver，将IntentFiler实例和Receiver实例传入注册，这样该Receiver就能收到所有值为所添加的action的广播

networkChangeReceiver = new NetworkChangeReceiver();
registerReceiver(networkChangeReceiver, intentFilter);

注意：动态注册的广播必须在onDestroy中注销

@Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
        localBroadcastManager.unregisterReceiver(localReceiver);
    }

小技巧

@Override
public void onReceive(Context context, Intent intent) {
    ConnectivityManager connectionManager = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connectionManager.getActiveNetworkInfo();
    if (networkInfo != null && networkInfo.isAvailable()) {
               Toast.makeText(context, "network is available",Toast.LENGTH_SHORT).show();
          } else {
        Toast.makeText(context, "network is unavailable",Toast.LENGTH_SHORT).show();

• 通过getSystemService()方法得到ConnectivityManager的实例，调用它的getActiveNetwork-Info()得到NetWorkInfo的实例，接着调用NetworkInfo的isAvailable()，网络权限要注册。

静态注册

利用AS的设置，可以快速（不用在AndroidManifest中注册），补充对应的action及权限

注意：在 onReceive()方法中不允许开启子线程，如果onRecceive方法执行较长时间没有结束会报错

使用本地广播

    private LocalReceiver localReceiver;
    private LocalBroadcastManager localBroadcastManager;
    onCreate(){
    ……
    localBroadcastManager = LocalBroadcastManager.getInstance(this); // 获取实例
     Intent intent = new Intent("com.example.broadcasttest.LOCAL_BROADCAST");
                localBroadcastManager.sendBroadcast(intent); // 发送本地广播
                intentFilter = new IntentFilter();
        intentFilter.addAction("com.example.broadcasttest.LOCAL_BROADCAST");
        localReceiver = new LocalReceiver();
        localBroadcastManager.registerReceiver(localReceiver, intentFilter); // 注册本地广播监听器
        }
/*
记得在onDestory()里注销
*/
localBroadcastManager.unregisterReceiver(localReceiver);
         
 class LocalReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context, "received local broadcast", Toast.LENGTH_SHORT).show();
        }