蓝牙低功耗设备扫描失败并出现异常

Question

我指的是开发者文档来扫描 BLE 设备 -

http://developer.android.com/guide/topics/connectivity/bluetooth-le.html

在我的活动类LookUpActivity 中，我在单击按钮时调用了一个方法findBLE()-

//This will scan BLE devices
public void findBLE()
{
    Intent intent = new Intent(LookUpActivity.this, DeviceScanActivity.class);
    startActivity(intent);
}

但出现以下异常 -

Could not find class 'com.testapp.main.DeviceScanActivity$1', 
referenced from method com.testapp.main.DeviceScanActivity.<init>


com.testapp.main fatal error : com.testapp.main.DeviceScanActivity$1
java.lang.NoClassDefFoundError: com.testapp.main.DeviceScanActivity$1   
at com.testapp.main.DeviceScanActivity.<init>(DeviceScanActivity.java:179)

DeviceScanActivity.java ---

/**
 * Activity for scanning and displaying available Bluetooth LE devices.
 */
@SuppressLint("NewApi")
public class DeviceScanActivity extends ListActivity {
    private LeDeviceListAdapter mLeDeviceListAdapter;
    private BluetoothAdapter mBluetoothAdapter;
    private boolean mScanning;
    private Handler mHandler;

    private static final int REQUEST_ENABLE_BT = 1;
    // Stops scanning after 10 seconds.
    private static final long SCAN_PERIOD = 10000;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mHandler = new Handler();
    }

    @Override
    protected void onResume() {
        super.onResume();

        // Ensures Bluetooth is enabled on the device.  If Bluetooth is not currently enabled,
        // fire an intent to display a dialog asking the user to grant permission to enable it.
        if (!mBluetoothAdapter.isEnabled()) {
            if (!mBluetoothAdapter.isEnabled()) {
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
            }
        }

        // Initializes list view adapter.
        mLeDeviceListAdapter = new LeDeviceListAdapter();
        setListAdapter(mLeDeviceListAdapter);
        scanLeDevice(true);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        // User chose not to enable Bluetooth.
        if (requestCode == REQUEST_ENABLE_BT && resultCode == Activity.RESULT_CANCELED) {
            finish();
            return;
        }
        super.onActivityResult(requestCode, resultCode, data);
    }

    @Override
    protected void onPause() {
        super.onPause();
        scanLeDevice(false);
        mLeDeviceListAdapter.clear();
    }

    private void scanLeDevice(final boolean enable) {
        if (enable) {
            // Stops scanning after a pre-defined scan period.
            mHandler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    mScanning = false;
                    mBluetoothAdapter.stopLeScan(mLeScanCallback);
                }
            }, SCAN_PERIOD);

            mScanning = true;
            mBluetoothAdapter.startLeScan(mLeScanCallback);
        } else {
            mScanning = false;
            mBluetoothAdapter.stopLeScan(mLeScanCallback);
        }
    }

    // Adapter for holding devices found through scanning.
    private class LeDeviceListAdapter extends BaseAdapter {
        private ArrayList<BluetoothDevice> mLeDevices;
        private LayoutInflater mInflator;

        public LeDeviceListAdapter() {
            super();
            mLeDevices = new ArrayList<BluetoothDevice>();
            mInflator = DeviceScanActivity.this.getLayoutInflater();
        }

        public void addDevice(BluetoothDevice device) {
            if(!mLeDevices.contains(device)) {
                mLeDevices.add(device);
            }
        }

        public BluetoothDevice getDevice(int position) {
            return mLeDevices.get(position);
        }

        public void clear() {
            mLeDevices.clear();
        }

        @Override
        public int getCount() {
            return mLeDevices.size();
        }

        @Override
        public Object getItem(int i) {
            return mLeDevices.get(i);
        }

        @Override
        public long getItemId(int i) {
            return i;
        }

        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {
            ViewHolder viewHolder;
            // General ListView optimization code.
            if (view == null) {
                view = mInflator.inflate(R.layout.mapentries, null);
                viewHolder = new ViewHolder();
                viewHolder.deviceAddress = (TextView) view.findViewById(R.id.entriestitle);
                //viewHolder.deviceName = (TextView) view.findViewById(R.id.device_name);
                view.setTag(viewHolder);
            } else {
                viewHolder = (ViewHolder) view.getTag();
            }

            BluetoothDevice device = mLeDevices.get(i);
            final String deviceName = device.getName();
           /* if (deviceName != null && deviceName.length() > 0)
                viewHolder.deviceName.setText(deviceName);
            else
                viewHolder.deviceName.setText(R.string.unknown_device);*/

            viewHolder.deviceAddress.setText(device.getAddress());

            return view;
        }
    }

    // Device scan callback.
    private BluetoothAdapter.LeScanCallback mLeScanCallback =
            new BluetoothAdapter.LeScanCallback() { //This is line 179 causing error...

        @Override
        public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    mLeDeviceListAdapter.addDevice(device);
                    mLeDeviceListAdapter.notifyDataSetChanged();
                }
            });
        }
    };

    static class ViewHolder {
        //TextView deviceName;
        TextView deviceAddress;
    }
}

更新：

为了更具体，我从 --- 下载了 BLE 的确切项目代码

http://developer.android.com/samples/BluetoothLeGatt/project.html

即使使用项目中提到的代码，也再次遇到相同的异常。

这次是错误控制台--

FATAL EXCEPTION: main
java.lang.NoClassDefFoundError:   
com.example.android.bluetoothlegatt
.DeviceScanActivity$1
at com.example.android.bluetoothlegatt.DeviceScanActivity.
<init>  (DeviceScanActivity.java:250)

Answer 1

您必须执行全面检查以查看设备是否支持蓝牙低功耗 (BLE)。该设备可能运行 Android 4.3 或更高版本，但缺少 BLE 所需的硬件。 Nexus 7 (2012) 就是这种设备的一个例子。代码如下：

  private boolean bleCheck() {
    boolean result = false;
    if (getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
      mBluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
      if (mBluetoothManager != null) {
        mBluetoothAdapter = mBluetoothManager.getAdapter();
        if (mBluetoothAdapter != null) {
          if (mBluetoothAdapter.isEnabled()) {
            result = true;
          }
        }
      }
    }
    return result;
  }