Android学习手记(4) BroadcastReceiver监听电池信息

　　Android 中，Broadcast是一种在应用程序之间进行传输信息的机制。BroadcastReceiver对发送过来的Broadcast进行过滤和响应。根据这种机制，我们可以获取电池现有电量等信息。

1、实例化BroadcastReceiver

　　在接受信息的时候，可以通过intent.getAction().equals(Intent.ACTION_BATTERY_CHANGED)来判断接收的信息是否为电池电量变化信息。如果是，就获取此信息的详细情况。

private BroadcastReceiver batteryInfoReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
if(intent.getAction().equals(Intent.ACTION_BATTERY_CHANGED)){
int level = intent.getIntExtra("level", 0);
int scale = intent.getIntExtra("scale", 100);
batteryView.setText("BatteryLevel " + String.valueOf(level*100/scale)+"%");
}
}
};

2、注册消息接收器

　　在onResume方法内注册消息接收器用来接收消息

registerReceiver(batteryInfoReceiver, new intentFilter(Intent.ACTION_BATTERY_CHANGED));

3、注销消息接收器

　　在onPause方法内注销消息接收器

unregisterReceiver(batteryInfoReceiver);

4、完整代码

public class MainActivity extends AppCompatActivity {

private TextView batteryView;
private BroadcastReceiver batteryInfoReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
if(intent.getAction().equals(Intent.ACTION_BATTERY_CHANGED)){
int level = intent.getIntExtra("level", 0);
int scale = intent.getIntExtra("scale", 100);
batteryView.setText("BatteryLevel " + String.valueOf(level*100/scale)+"%");
}
}
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

batteryView = (TextView) this.findViewById(R.id.batteryView);
}

@Override
protected void onResume(){
super.onResume();
registerReceiver(batteryInfoReceiver, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
}

@Override
protected void onPause(){
super.onPause();
unregisterReceiver(batteryInfoReceiver);
}
}