在蓝牙 LE 连接中使用 ScanFilter 时没有回调

Question

我想设置一个 ScanFilter 以根据其广告数据扫描 BLE 设备：名称、服务 UUID 及其制造数据的第一个字符。问题是：当我使用 ScanFilter 时，没有回调，这意味着没有调用 .onScanResult()。

设备名称是正确的，因为我已经通过在回调中找到设备进行了测试。当我不使用 ScanFilter 时，有回调，可以通过名称找到设备。并且可以成功连接到设备。

这是我有问题的代码。你能帮忙指出它的问题吗？

另外，我还有一个问题：.setManufacturerData()的三个参数如何输入？

protected void scan(){

    List<ScanFilter> filters = new ArrayList<>();
    ScanFilter filterName = new ScanFilter.Builder().setDeviceName(this.mDeviceName).build();
    filters.add(filterName);
    //ScanFilter filterUUID = new ScanFilter.Builder().setServiceUuid(ParcelUuid.fromString("00001814-0000-1000-8000-00805F9B34FB")).build();
    //filters.add(filterUUID);
    //ScanFilter filterManu = new ScanFilter.Builder().setManufacturerData().build();
    //filters.add(filterManu);

    ScanSettings settings = (new Builder()).setScanMode(2).build();
    this.mBluetoothLeScanner.startScan(filters, settings, this);
    this.mScanning = true;
}

@Override
    public void onScanResult(int callbackType, ScanResult result) {
        super.onScanResult(callbackType, result);
        BluetoothDevice _device = result.getDevice();
                Log.i("onScanResult", " callback function is being called");

        // find device by name
        if (_device != null && _device.getName() != null && _device.getName().matches(this.mDeviceName) ) {
            this.stopScan();
            this.mDevice = _device;
            Log.i(TAG, "mac address : " + this.mDevice.getAddress() + ", name : " + this.mDevice.getName());
            this.mDeviceFoundLatch.countDown();
        }

        long m = mDeviceFoundLatch.getCount();
        Log.i("onResultscallbackLatch", String.valueOf(m));

    }

我遇到了这些错误：

E/ScanRecord: unable to parse scan record: [2, 1, 6, 3, 2, 20, 24, 2, -1, 82, 20, 9, 83, 116, 114, 105, 100, 97, 108, 121, 122, 101, 114, 32, 73, 78, 83, 73, 71, 72, 84, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

E/BluetoothServiceJni: An exception was thrown by callback 'btgattc_scan_result_cb'.

E/BluetoothServiceJni: java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object java.util.Map.get(java.lang.Object)' on a null object reference
        at android.bluetooth.le.ScanRecord.getServiceData(ScanRecord.java:121)
        at android.bluetooth.le.ScanFilter.matches(ScanFilter.java:305)
        at com.android.bluetooth.gatt.GattService.matchesFilters(GattService.java:659)
        at com.android.bluetooth.gatt.GattService.onScanResult(GattService.java:611)

这是正确的运行代码。我可以用它来找到设备。但我想通过制造数据过滤设备。扫描时是否必须设置过滤器？这里有没有根据制造数据过滤设备的方法？

protected void scan(){    
        ScanSettings settings = (new Builder()).setScanMode(2).build();
        this.mBluetoothLeScanner.startScan(null, settings, this);
        this.mScanning = true;
    }

    @Override
        public void onScanResult(int callbackType, ScanResult result) {
            super.onScanResult(callbackType, result);
            BluetoothDevice _device = result.getDevice();
            if (_device != null && _device.getName() != null && _device.getName().matches(this.mDeviceName) ) {
                this.stopScan();
                this.mDevice = _device;
                this.mDeviceFoundLatch.countDown();
            }
        }

Answer 1

确实是设备发送的数据无效。格式基本上是一个序列：

数据长度（包括字段类型）
字段类型
数据

所以如果我们拆分数据，我们得到：

2: length 2 bytes
1: field type "flags"
6: data (flags)

3: length 3 bytes
2: field type "partial 16 bit UUID"
20, 24: data (UUID bytes 0x14 0x18, that will be converted into the full UUID 00001814-0000-1000-8000-00805F9B34FB)

2: length 2 bytes
-1 (or 0xff): field type "manufacturer data"
82: data (manufacturer data)

20: length 20 bytes
9: field type "local name complete"
83, 116, 114, 105, 100, 97, 108, 121, 122, 101, 114, 32, 73, 78, 83, 73, 71, 72, 84: data (local name, decoded as "Stridalyzer INSIGHT")
0, 0, ...: ignored data

很遗憾，制造商数据无效。它至少需要 3 个字节（类型字段为 4 个字节），并以制造商 ID 的 2 个字节开头。所以在这一点上，Android 放弃解析并创建一个 ScanResult，根本没有数据。

所以你不会对过滤器有任何好感。相反，您需要自己过滤它。

Answer 2

终于成功了！这是我的解决方案：

由于制造商数据无效（见上面@code的解释），我们不能直接使用Android-provided函数-scanRecord.getManufacturerSpecificData()。相反，我使用以下代码手动解析广告：

@Override
public void onScanResult(int callbackType, ScanResult result) {
    super.onScanResult(callbackType, result);


    BluetoothDevice _device = result.getDevice();
    ScanRecord scanRecord = result.getScanRecord();
    byte[] byte_ScanRocord = scanRecord.getBytes();
    int isLeft = byte_ScanRocord[9];//the 9th byte stores the information that can be used to filter the device
    String byte_ScanRocord_str = Arrays.toString(byte_ScanRocord);
    Log.i("onScanRecordAdv",byte_ScanRocord_str);
    Log.i("onScanRecordisLeft",String.valueOf(isLeft));

    if (_device != null && _device.getName() != null && _device.getName().matches(this.mDeviceName) && isLeft == 76 ) {
        this.stopScan();
        this.mDevice = _device;
        Log.i("InsoleScanner", "mac address : " + this.mDevice.getAddress() + ", name : " + this.mDevice.getName());
        this.mDeviceFoundLatch.countDown();
    }
}

在蓝牙 LE 连接中使用 ScanFilter 时没有回调

no callback when using ScanFilter in Bluetooth LE Connection

android

bluetooth