BroadcastReceiver监听电量变化

　　用BroadcastReceiver监听电量的变化，可以实现BroadcastReceiver接收电量变化的广播，然后获取电量百分比信息。

　　BatteryChangedReceiver.java

public class BatteryChangedReceiver extends BroadcastReceiver{
    private static final String TAG="BatteryChangedReceiver";
    @Override
    public void onReceive(Context context,Intent intent){
        int currLevel=intent.getIntExtra(BatteryManager.EXTRA_LEVEL, 0);//当前电量
        int total=intent.getIntExtra(BatteryManager.EXTRA_SCALE, 1);//总电量
        int percent=currLevel*100/total;
        Log.i(TAG,"battery:"+percent+"%");
    }
}

　　在清单文件中注册广播接收者以及要拦截的Action：

<receiver android:name=".BatteryChangedReceiver">
    <intent-filter>
        <action android:name="android.intent.action.BATTERY_CHANGED"/>
    </intent-filter>
</receiver>

　　有些时候，我们需要立即获取电量，而不是等电量变化的广播，可以通过下面的方式：

Intent batteryIntent=getApplicationContext().registerReceiver(null,new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
int currLevel=batteryIntent.getIntExtra(BatteryManager.EXTRA_LEVEL,0);
int total=batteryIntent.getIntExtra(BatteryManager.EXTRA_SCALE,1);
int percent=currLevel*100/total;
Log.i("battery","battery:"+percent+"%");