Android BLE -读取字符

Question

我的建筑连接到一个切割硬件BLE ap。我使用的是三星Galaxy S3,Android版本4.3进行测试。我已经成功连接到远程设备，并且能够列出该设备的所有服务。问题是，我似乎无法阅读任何服务的特征。下面是displayGattServices函数的代码(直接取自Google的示例代码)——

// Demonstrates how to iterate through the supported GATT Services/Characteristics.
// In this sample, we populate the data structure that is bound to the ExpandableListView
// on the UI.
private void displayGattServices(List<BluetoothGattService> gattServices) {
    if (gattServices == null) return;
    String uuid = null;
    String unknownServiceString = getResources().getString(R.string.unknown_service);
    String unknownCharaString = getResources().getString(R.string.unknown_characteristic);
    ArrayList<HashMap<String, String>> gattServiceData = new ArrayList<HashMap<String, String>>();
    ArrayList<ArrayList<HashMap<String, String>>> gattCharacteristicData
            = new ArrayList<ArrayList<HashMap<String, String>>>();
    mGattCharacteristics = new ArrayList<ArrayList<BluetoothGattCharacteristic>>();
    // Loops through available GATT Services.
    for (BluetoothGattService gattService : gattServices) {
        HashMap<String, String> currentServiceData = new HashMap<String, String>();
        uuid = gattService.getUuid().toString();
        currentServiceData.put(
                LIST_NAME, SampleGattAttributes.lookup(uuid, unknownServiceString));
        currentServiceData.put(LIST_UUID, uuid);
        gattServiceData.add(currentServiceData);
        ArrayList<HashMap<String, String>> gattCharacteristicGroupData =
                new ArrayList<HashMap<String, String>>();
        List<BluetoothGattCharacteristic> gattCharacteristics =
                gattService.getCharacteristics();
        ArrayList<BluetoothGattCharacteristic> charas =
                new ArrayList<BluetoothGattCharacteristic>();
        // Loops through available Characteristics.
 for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) {
            charas.add(gattCharacteristic);
            HashMap<String, String> currentCharaData = new HashMap<String, String>();
            uuid = gattCharacteristic.getUuid().toString();
            currentCharaData.put(
                    LIST_NAME, SampleGattAttributes.lookup(uuid, unknownCharaString));
            currentCharaData.put(LIST_UUID, uuid);
            gattCharacteristicGroupData.add(currentCharaData);
        }
        mGattCharacteristics.add(charas);
        gattCharacteristicData.add(gattCharacteristicGroupData);
    }
    SimpleExpandableListAdapter gattServiceAdapter = new SimpleExpandableListAdapter(
            this,
            gattServiceData,
            android.R.layout.simple_expandable_list_item_2,
            new String[] {LIST_NAME, LIST_UUID},
            new int[] { android.R.id.text1, android.R.id.text2 },
            gattCharacteristicData,
            android.R.layout.simple_expandable_list_item_2,
            new String[] {LIST_NAME, LIST_UUID},
            new int[] { android.R.id.text1, android.R.id.text2 }
    );
    mGattServicesList.setAdapter(gattServiceAdapter);
}

这是服务代码-

   private void broadcastUpdate(final String action,
                             final BluetoothGattCharacteristic characteristic) {
    final Intent intent = new Intent(action);
    // This is special handling for the Heart Rate Measurement profile.  Data parsing is
    // carried out as per profile specifications:
    // http://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.heart_rate_measurement.xml
    if (UUID_HEART_RATE_MEASUREMENT.equals(characteristic.getUuid())) {
        int flag = characteristic.getProperties();
        int format = -1;
        if ((flag & 0x01) != 0) {
            format = BluetoothGattCharacteristic.FORMAT_UINT16;
            Log.d(TAG, "Heart rate format UINT16.");
        } else {
            format = BluetoothGattCharacteristic.FORMAT_UINT8;
            Log.d(TAG, "Heart rate format UINT8.");
        }
        final int heartRate = characteristic.getIntValue(format, 1);
        Log.d(TAG, String.format("Received heart rate: %d", heartRate));
        intent.putExtra(EXTRA_DATA, String.valueOf(heartRate));
    } else {
        // For all other profiles, writes the data formatted in HEX.
        final byte[] data = characteristic.getValue();
        if (data != null && data.length > 0) {
            final StringBuilder stringBuilder = new StringBuilder(data.length);
            for(byte byteChar : data)
                stringBuilder.append(String.format("%02X ", byteChar));
            intent.putExtra(EXTRA_DATA, new String(data) + "n" + stringBuilder.toString());
        }
    }
    sendBroadcast(intent);
}

    @Override
    public void onCharacteristicRead(BluetoothGatt gatt,
                                     BluetoothGattCharacteristic characteristic,
                                     int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
        }
    }
    @Override
    public void onCharacteristicChanged(BluetoothGatt gatt,
                                        BluetoothGattCharacteristic characteristic) {
        broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
    }
};

每当我尝试检索字符时，gattService.getCharacteristics()返回一个空列表。我做得对吗，是硬件出了问题，还是我遗漏了什么?

谢谢

Answer 1

每当我尝试检索字符时，gattService.getCharacteristics()返回一个空列表。

您收到空列表，因为支持BLE芯片的远端设备不支持任何特性。

问题是硬件

这不是Galaxy S3设备的问题，实际上问题出在支持BLE芯片(固件端)的远程设备上，比如Galaxy Gear…如果Galaxy Gear设备不支持任何特性，您的Galaxy S3将无法找到任何特性。

p/s:你从样本代码得到的代码是好的。

Answer 2

您的代码似乎是正确的。

看不见特征可能有两个原因:

1)硬件不支持任何特性。测试这一点的最好方法，可能是安装一些扫描应用程序，允许您探索BLE设备。(android上有很多可用的，例如SensorTag，它也可以扫描其他设备)或者更好的一些iOS，那里的BLE堆栈更稳定。

2) android BLE堆栈不完全稳定(正如在这里的许多线程中讨论的那样)-你做了一些事情，在内部崩溃了，出路是尝试禁用和启用BT，或者，如果这没有帮助，重新启动设备。但在本例中，这是不可能的，因为您可以看到服务。