在Android上难以从BLE软件包中读取数据

目前,由于传感器不可用,我正在使用另一个安卓设备作为BLE广告客户。注意,我没有连接到设备,我只是阅读了广告包。

private void advertise() {
    BluetoothLeAdvertiser advertiser = BluetoothAdapter.getDefaultAdapter().getBluetoothLeAdvertiser();

    AdvertiseSettings settings = new AdvertiseSettings.Builder()
            .setAdvertiseMode( AdvertiseSettings.ADVERTISE_MODE_LOW_LATENCY )
            .setTxPowerLevel( AdvertiseSettings.ADVERTISE_TX_POWER_HIGH )
            .setConnectable(false)
            .build();

    ParcelUuid pUuid = new ParcelUuid( UUID.fromString( getString( R.string.ble_uuid ) ) );
    byte[] mdata = "Hello".getBytes(Charset.forName("UTF-8"));

    AdvertiseData data = new AdvertiseData.Builder()
            .setIncludeDeviceName( true )
            .addServiceUuid( pUuid )
            .addServiceData( pUuid, mdata )
            .build();

    AdvertiseCallback advertisingCallback = new AdvertiseCallback() {
        @Override
        public void onStartSuccess(AdvertiseSettings settingsInEffect) {
            super.onStartSuccess(settingsInEffect);
        }

        @Override
        public void onStartFailure(int errorCode) {
            Log.e( "BLE", "Advertising onStartFailure: " + errorCode );
            super.onStartFailure(errorCode);
        }
    };

这部分工作得很好,因为我使用BLE scanner应用程序接收的原始数据就是我想要发送的数据。

问题出在接受方。我要做的是:

private void discover() {
    List<ScanFilter> filters = new ArrayList<ScanFilter>();

    ScanFilter filter = new ScanFilter.Builder()
            .setServiceUuid( new ParcelUuid(UUID.fromString( getString(R.string.ble_uuid ) ) ) )
            .build();
    filters.add( filter );

    ScanSettings settings = new ScanSettings.Builder()
            .setScanMode( ScanSettings.SCAN_MODE_LOW_LATENCY )
            .build();

    mBluetoothLeScanner.startScan(filters, settings, mScanCallback);

    mHandler.postDelayed(new Runnable() {
        @Override
        public void run() {
            mBluetoothLeScanner.stopScan(mScanCallback);
        }
    }, 10000);
}

我的scanCallBack函数如下:

private ScanCallback mScanCallback = new ScanCallback() {
        @Override
        public void onScanResult(int callbackType, ScanResult result) {
            super.onScanResult(callbackType, result);
            if( result == null
                    || result.getDevice() == null
                    || TextUtils.isEmpty(result.getDevice().getName()) )
                return;

        StringBuilder builder = new StringBuilder( result.getDevice().getName());
        for(int j = 0; j < result.getScanRecord().getServiceUuids().size(); j++){
            builder.append("\n");
            builder.append("Result no. " + j);
            builder.append("\n");
            builder.append(result.getScanRecord().getServiceUuids().get(j));
            builder.append("\n");
            builder.append("Service data: ");
            builder.append("\n");
            builder.append(result.getScanRecord().getServiceData(result.getScanRecord().getServiceUuids().get(j)));
        }
        mText.setText(builder.toString());
    }

这段代码在我试图读取数据时总是返回null。

请在这件事上给我一些智慧。