广播的动作分别为：注册、发送、接收。

1. 定义接收器

public class MyReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        
    }
}

2. 注册广播

final MyReceiver[] receivers = {null};
        Button registerBroad = findViewById(R.id.registerBroadcast);
        registerBroad.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                receivers[0] = new MyReceiver();
                IntentFilter intentFilter = new IntentFilter();
                intentFilter.addAction("sendMSG");
                registerReceiver(receivers[0],intentFilter);
            }
        });

3. 发送广播

Button sendBroadcast = findViewById(R.id.sendBroadcast);
        sendBroadcast.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent();
                intent.setAction("sendMSG");
                intent.putExtra("msg","it is the Broadcast message");
                sendBroadcast(intent);
            }
        });

4. 定义接收到广播后的行为

public class MyReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Log.i("Test","MSG received"+intent.getStringExtra("msg"));
    }
}