Question

我在设备扫描活动中遇到问题。我想要scan附近的所有bluetooth devices并在UI上打印它们。但我得到的运行时错误与Receiving broadcast error for Bluetooth discovery相同。

public class MainActivity extends ActionBarActivity {

    BluetoothAdapter mBluetoothAdapter;
    private int REQUEST_ENABLE_BT = 1000;
    public ArrayList<String> deviceArrayList = new ArrayList<>();
    public ArrayList<BluetoothDevice> deviceList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        if (mBluetoothAdapter == null) {
            // Device does not support Bluetooth
            Toast.makeText(this, "Device Doesn't Support Bluetooth!!!", Toast.LENGTH_LONG).show();
            return;
        }
        if (!mBluetoothAdapter.isEnabled()) {
            Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT );
        }
        scanStart();
    }

    public void scanStart() {
        // TODO Auto-generated method stub

        //Adding Paired Devices into ArrayList
        addPairedDevices();

        if(mBluetoothAdapter.isDiscovering()){
            mBluetoothAdapter.cancelDiscovery();
        }
        if(mBluetoothAdapter.startDiscovery() == true){
            Toast.makeText(this, "Searching...", Toast.LENGTH_LONG).show();
        }
        else{
            Toast.makeText(this, "Bluetooth Adapter got Null Value", Toast.LENGTH_SHORT).show();
        }

        // Register the BroadcastReceiver
        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        this.registerReceiver(requestReciever, filter); // Don't forget to unregister during onDestroy  

        try {
            Thread.sleep(12000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        //Printing Device List on UI
        ListView lv = new ListView(this);
        ArrayAdapter<String> listAdapter = new ArrayAdapter<>(this, R.layout.print_device_list, deviceArrayList);
        lv.setAdapter(listAdapter);
        setContentView(lv);
        if(deviceArrayList.size()<=0){
            Toast.makeText(this, "No Devices Found...", Toast.LENGTH_LONG).show();
        }
    }


    public void addPairedDevices() {
        // TODO Auto-generated method stub
        // get paired devices
        Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
        // If there are paired devices
        if (pairedDevices.size() > 0) {
            // Loop through paired devices
            for (BluetoothDevice device : pairedDevices) {
                // Add the name and address to an array adapter to show in a ListView
                deviceArrayList.add(device.getName() + "\n" + device.getAddress() + "\n" + device.getUuids()[0].getUuid());
                deviceList.add(device);
            }
        }
    }


    private BroadcastReceiver requestReciever = new BroadcastReceiver(){

        public void onReceive(Context context, Intent intent) {
            if (intent == null) {
                return;
            }
            String action = intent.getAction();

            if(BluetoothDevice.ACTION_FOUND.equals(action)){
                Log.d("BT", "Device Found");
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                if(device!=null){
                    if(device.getName() != null && device.getName().length() > 0){
                        deviceArrayList.add(device.getName()+"\n"+device.getAddress()+"\n"+device.getUuids()[0].getUuid());
                        deviceList.add(device);
                    }
                }
            }
        };
    };


    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        // TODO Auto-generated method stub
        super.onActivityResult(requestCode, resultCode, data);

        if(requestCode == REQUEST_ENABLE_BT){
            if(resultCode == Activity.RESULT_CANCELED){
                Toast.makeText(this, "Uesr Doesn't want to switch on Bluetooth!!!", Toast.LENGTH_LONG).show();
                return;
            }
        }
    }



    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        if(mBluetoothAdapter != null){
            mBluetoothAdapter.cancelDiscovery();
        }
        if(requestReciever!=null)
            unregisterReceiver(requestReciever);
        Toast.makeText(this, "Bluetooth App Stopped", Toast.LENGTH_LONG).show();
    }
}

Answer 1

device.getUuids() - 这里你有一个Null，这就是你在这里有错误的原因。请使用它来检查此变量。

接收蓝牙发现的广播错误 - 通过startDiscovery（）方法接收意图的onReceive（）方法出错

1 个答案: