Android4.4开发之电池低电量告警提示原理与实现方法分析

public void start() {
......
  //注册intent, 主要关注的是ACTION_BATTERY_CHANGED消息。
  // Register for Intent broadcasts for...
  IntentFilter filter = new IntentFilter();
  filter.addAction(Intent.ACTION_BATTERY_CHANGED);
  filter.addAction(Intent.ACTION_SCREEN_OFF);
  filter.addAction(Intent.ACTION_SCREEN_ON);
  mContext.registerReceiver(mIntentReceiver, filter, null, mHandler);
}

private BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
  @Override
  public void onReceive(Context context, Intent intent) {
    String action = intent.getAction();
    if (action.equals(Intent.ACTION_BATTERY_CHANGED)) {
      ......
      mBatteryStatus = intent.getIntExtra(BatteryManager.EXTRA_STATUS,
          BatteryManager.BATTERY_STATUS_UNKNOWN);
      ......
      if (!plugged
          && (bucket < oldBucket || oldPlugged) && mBatteryStatus != BatteryManager.BATTERY_STATUS_UNKNOWN && bucket < 0) { showLowBatteryWarning(); ...... } } };