在连接到GATT服务器时从未调用过onServicesDiscovered

Question

我有一个蓝牙耳机,它与我的Nexus 5X(运行Android 7.1)配对,我想连接到耳机的GATT服务器.我用以下代码尝试了它:

private BluetoothGattCallback btleGattCallback = new BluetoothGattCallback() {
    @Override
    public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
        Log.d(TAG, "onConnectionStateChange: " + status + ", " + newState);

        if(newState == STATE_CONNECTED) {
            Log.d(TAG, "Device connected");
            boolean ans = gatt.discoverServices();
            Log.d(TAG, "Discover Services started: " + ans);
        }
    }

    @Override
    public void onServicesDiscovered(BluetoothGatt gatt, int status) {
            Log.d(TAG, "Number of Services: " + gatt.getServices().size());
    }
};

public void onDeviceClicked(BluetoothDevice device) {
    BluetoothGatt gatt = device.connectGatt(this, false, btleGattCallback);
    Log.d(TAG, "Connected to GATT: " + gatt.connect());
}

如果我在我的UI中单击耳机,onDeviceClicked则会调用此日志输出:

<!-- language: lang-none -->
Connected to GATT: true
onConnectionStateChange: 0, 2    // GATT_SUCCESS, STATE_CONNECTED
Device connected
Discover Services started: true

你可以看到onServicesDiscovered永远不会被解雇.我试着打电话connectGatt给TRANSPORT_LE(参考),但后来我得到了onConnectionStateChange: 133, 0.我也发现了这个问题,这就是我gatt.connect()在答案二中提到的方法.

你有什么想法我没有得到onServicesDiscovered回调吗？

Answer 1

Android上的BLE可能有点挑剔.

确保在UI线程上调用mBluetoothGatt.discoverServices().

if(newState == STATE_CONNECTED) {
    Log.d(TAG, "Device connected");
    new Handler(Looper.getMainLooper()).post(new Runnable() {
        @Override
        public void run() {
            boolean ans = mBluetoothGatt.discoverServices();
            Log.d(TAG, "Discover Services started: " + ans);
        }
    });
}

还可以尝试创建BluetoothGatt gatt字段变量而不是局部变量.

如果您正在进行任何重要工作,请尝试使用掩盖所有特性的库,以便您可以专注于高级逻辑. https://github.com/Polidea/RxAndroidBle.

这是一个如何阅读特征的例子.

        connectionObservable
                .flatMap(rxBleConnection -> rxBleConnection.readCharacteristic(characteristicUuid))
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(bytes -> {
                    readOutputView.setText(new String(bytes));
                    readHexOutputView.setText(HexString.bytesToHex(bytes));
                    writeInput.setText(HexString.bytesToHex(bytes));
                }, this::onReadFailure);

或者使用Java 7语法

        connectionObservable
                .flatMap(new Func1<RxBleConnection, Observable<byte[]>>() {
                    @Override
                    public Observable<byte[]> call(RxBleConnection rxBleConnection) {
                        return rxBleConnection.readCharacteristic(characteristicUuid);
                    }
                })
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Subscriber<byte[]>() {
                    @Override
                    public void onCompleted() {

                    }

                    @Override
                    public void onError(Throwable e) {
                        onReadFailure(e);
                    }

                    @Override
                    public void onNext(byte[] bytes) {
                        readOutputView.setText(new String(bytes));
                        readHexOutputView.setText(HexString.bytesToHex(bytes));
                        writeInput.setText(HexString.bytesToHex(bytes));
                    }
                });

Answer 2

对我来说真正有用的东西是在建立连接后等待大约600ms,然后开始服务发现.