安卓开发学习笔记—————《第一行代码》第五章 广播机制

Android中的广播分为：标准广播（所有广播接收器几乎会在同一时刻接收到这条广播消息）和有序广播（同一时刻只有一个广播接收器能够收到这条广播消息。

广播接收器动态注册广播

如监听网络变化：

public class MainActivity extends AppCompatActivity {

    private IntentFilter intentFilter;
    private NetworkChangeReceiver networkChangeReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        intentFilter = new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        networkChangeReceiver = new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver, intentFilter);
    }

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

    class NetworkChangeReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context, "network changes", Toast.LENGTH_SHORT).show();
        }
    }
}