How to get the battery level after connect to the BLE device?

I am developing an application where I have to connect to Bluetooth device on Android 4.3.

And I want to get the battery level by using Battery_Service and Battery_Level.

public class BluetoothLeService extends Service {

    private static final UUID Battery_Service_UUID =
                UUID.fromString("0000180F-0000-1000-8000-00805f9b34fb");

    private static final UUID Battery_Level_UUID =
                UUID.fromString("00002a19-0000-1000-8000-00805f9b34fb");


    public void getbattery() {

        BluetoothGattService batteryService = mBluetoothGatt.getService(Battery_Service_UUID);
        if(batteryService == null) {
            Log.d(TAG, "Battery service not found!");
            return;
        }

        BluetoothGattCharacteristic batteryLevel = batteryService.getCharacteristic(Battery_Level_UUID);
        if(batteryLevel == null) {
            Log.d(TAG, "Battery level not found!");
            return;
        }

         mBluetoothGatt.readCharacteristic(batteryLevel);
    　　　　　// What should I do that I can get the battery level ??
         Log.d(TAG, "Battery level " + mBluetoothGatt.readCharacteristic(batteryLevel););
    }

}

But the value of mBluetoothGatt.readCharacteristic(batteryLevel); is not the battery level value

How to read the battery?

I have solved this problem.

public class BluetoothLeService extends Service {

    private static final UUID Battery_Service_UUID = UUID.fromString("0000180F-0000-1000-8000-00805f9b34fb");
    private static final UUID Battery_Level_UUID = UUID.fromString("00002a19-0000-1000-8000-00805f9b34fb");

    public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {

        if(status == BluetoothGatt.GATT_SUCCESS) {
            broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
        }
    }


    private void broadcastUpdate(final String action, final BluetoothGattCharacteristic characteristic) {

        final Intent intent = new Intent(action);   
        Log.v(TAG, "characteristic.getStringValue(0) = " + characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_UINT8, 0));
        intent.putExtra(DeviceControl.EXTRAS_DEVICE_BATTERY, characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_UINT8, 0));  
        sendBroadcast(intent);
    }

    public void getbattery() {

        BluetoothGattService batteryService = mBluetoothGatt.getService(Battery_Service_UUID);
        if(batteryService == null) {
            Log.d(TAG, "Battery service not found!");
            return;
        }

        BluetoothGattCharacteristic batteryLevel = batteryService.getCharacteristic(Battery_Level_UUID);
        if(batteryLevel == null) {
            Log.d(TAG, "Battery level not found!");
            return;
        }
        mBluetoothGatt.readCharacteristic(batteryLevel);
        Log.v(TAG, "batteryLevel = " + mBluetoothGatt.readCharacteristic(batteryLevel));
    }
}

When you call the function getbattery() , it will call onCharacteristicRead. and onCharacteristicRead will call broadcastUpdate and transmit the characteristic and action to it.

And the characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_UINT8, 0) in broadcastUpdate is the battery value of the BLE device.