Java 如何知道手机是否正在充电

我需要（通过我的应用程序）知道Android设备是否正在充电。有什么想法吗？谢谢

以下是有效的代码：

Intent bat = loader.registerReceiver(null, new
        IntentFilter(Intent.ACTION_BATTERY_CHANGED));
int level = bat.getIntExtra("level", 0);
int scale = bat.getIntExtra("scale", 100);
return level * 100 / scale; 

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我发现的一件事是，如果你的手机电池电量为100%，你就不会收到充电通知。有些人指的是充电，而另一些人指的是当它有外部电源时，不管是不是100%。我把它们归为一个，如果任何条件为真，那么我返回真

public static boolean isPhonePluggedIn(Context context){
    boolean charging = false;

    final Intent batteryIntent = context.registerReceiver(null, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
    int status = batteryIntent.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
    boolean batteryCharge = status==BatteryManager.BATTERY_STATUS_CHARGING;

    int chargePlug = batteryIntent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
    boolean usbCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_USB;
    boolean acCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_AC;

    if (batteryCharge) charging=true;
    if (usbCharge) charging=true;
    if (acCharge) charging=true; 

    return charging;
}

public static boolean isPhonePluggedIn(Context context){
    boolean charging = false;

    final Intent batteryIntent = context.registerReceiver(null, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
    int status = batteryIntent.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
    boolean batteryCharge = status==BatteryManager.BATTERY_STATUS_CHARGING;

    int chargePlug = batteryIntent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
    boolean usbCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_USB;
    boolean acCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_AC;

    if (batteryCharge) charging=true;
    if (usbCharge) charging=true;
    if (acCharge) charging=true; 

    return charging;
}