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。

 1 private BroadcastReceiver batteryInfoReceiver = new BroadcastReceiver() {
 2         @Override
 3         public void onReceive(Context context, Intent intent) {
 4             if(intent.getAction().equals(Intent.ACTION_BATTERY_CHANGED)){
 5                 int level = intent.getIntExtra("level", 0);
 6                 int scale = intent.getIntExtra("scale", 100);
 7                 batteryView.setText("BatteryLevel " + String.valueOf(level*100/scale)+"%");
 8             }
 9         }
10     };

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

 1 public class MainActivity extends AppCompatActivity {
 2 
 3     private TextView batteryView;
 4     private BroadcastReceiver batteryInfoReceiver = new BroadcastReceiver() {
 5         @Override
 6         public void onReceive(Context context, Intent intent) {
 7             if(intent.getAction().equals(Intent.ACTION_BATTERY_CHANGED)){
 8                 int level = intent.getIntExtra("level", 0);
 9                 int scale = intent.getIntExtra("scale", 100);
10                 batteryView.setText("BatteryLevel " + String.valueOf(level*100/scale)+"%");
11             }
12         }
13     };
14 
15     @Override
16     protected void onCreate(Bundle savedInstanceState) {
17         super.onCreate(savedInstanceState);
18         setContentView(R.layout.activity_main);
19 
20         batteryView = (TextView) this.findViewById(R.id.batteryView);
21     }
22 
23     @Override
24     protected void onResume(){
25         super.onResume();
26         registerReceiver(batteryInfoReceiver, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
27     }
28 
29     @Override
30     protected void onPause(){
31         super.onPause();
32         unregisterReceiver(batteryInfoReceiver);
33     }
34 }