我正在尝试简单地从银河S3读取和写入Hello World到连接到虚拟串行端口的blueradio软件狗.但我越来越

Unhandled exception: java.lang.NullPointerException

每当我打电话

gatt.readCharacteristic(characteristic);

我用它来定义特征

private static final UUID MY_UUID = UUID.fromString("00001801-0000-1000-8000-00805f9b34fb");
private static final UUID charUUID = UUID.fromString("00002a01-0000-1000-8000-00805f9b34fb");
characteristic = gatt.getService(MY_UUID).getCharacteristic(charUUID);

当我这样调用discoverServices()时,我从LogCat中获取了UUID

D/BluetoothGatt(7083): discoverServices() - device: EC:FE:7E:11:12:A4
D/BluetoothGatt(7083): onGetService() - Device=EC:FE:7E:11:12:A4 UUID=00001800-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetService() - Device=EC:FE:7E:11:12:A4 UUID=00001801-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetService() - Device=EC:FE:7E:11:12:A4 UUID=0000180f-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetService() - Device=EC:FE:7E:11:12:A4 UUID=da2b84f1-6279-48de-bdc0-afbea0226079
D/BluetoothGatt(7083): onGetCharacteristic() - Device=EC:FE:7E:11:12:A4 UUID=00002a00-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetCharacteristic() - Device=EC:FE:7E:11:12:A4 UUID=00002a01-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetCharacteristic() - Device=EC:FE:7E:11:12:A4 UUID=00002a02-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetCharacteristic() - Device=EC:FE:7E:11:12:A4 UUID=00002a03-0000-1000-8000-00805f9b34fb

这是我不确定我是否做对的地方,我不知道如何为特性和服务获取正确的UUID

Beloiw是我的完整回调函数

private BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {

    public void testFunction(BluetoothGatt gatt){
        Log.d(TAG, "In Test Function");
        gatt.readRemoteRssi();
        BluetoothGattCharacteristic characteristic;
        characteristic = gatt.getService(MY_UUID).getCharacteristic(charUUID);
        characteristic.setValue("Hello World");
        gatt.readCharacteristic(characteristic);
    }
     @Override
    public void onConnectionStateChange(BluetoothGatt gatt, int status,
            int newState) {


            gatt.discoverServices();


    }


@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
    Log.d(TAG, "Services Discovered: "+ status);
    //mHandler.sendMessage(Message.obtain(null, MSG_PROGRESS, "Enabling Sensors..."));
    /*
     * With services discovered, we are going to reset our state machine and start
     * working through the sensors we need to enable
     */
            testFunction(gatt);
}


public void     onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic){
    Log.d(TAG, "Characteristic Changed: "+ characteristic.getValue());
}

public void     onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status){
    Log.d(TAG, "Characteristic Read: "+ status);
}

public void     onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status){
    Log.d(TAG, "Characteristic Write: "+ status);
}



public void     onDescriptorRead(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status){
    Log.d(TAG, "Descriptor Read: "+ status);
}

public void     onDescriptorWrite(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status){
    Log.d(TAG, "Descriptor Write: "+ status);
}

public void     onReadRemoteRssi(BluetoothGatt gatt, int rssi, int status){
    Log.d(TAG, "Read Rssi: "+ status);
}

public void     onReliableWriteCompleted(BluetoothGatt gatt, int status){
    Log.d(TAG, "Reliable Write: "+ status);
}


};

解决方法:

UUID由bluetooth.org预定义,它定义了前缀,例如00001800,最后一部分“ 0000-1000-8000-00805f9b34fb”相同.

请参阅预定义的UUID here列表.