Question

我正在尝试在屏幕关闭时保持蓝牙连接。所以我创建了一个应用程序，你可以发现周围的蓝牙设备，并从列表中选择。然后将选择的蓝牙设备传递给后台服务类，后者将处理其余部分。但是当我尝试从意图中获取设备时，我得到空指针。任何帮助将不胜感激。

这是我的代码段

    @Override
    public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
    if(btAdapter.isDiscovering()){
        btAdapter.cancelDiscovery();
    }
    if(listAdapter.getItem(arg2).contains("Paired")){

        BluetoothDevice selectedDevice = devices.get(arg2);

        Intent intent = new Intent(this,backgroundService.class);
        if(selectedDevice == null)
            Log.i(backgroundService.EXTRA_MESSAGE, "I am telling you it is null");
        intent.putExtra(backgroundService.EXTRA_MESSAGE, (Parcelable)selectedDevice);
        startService(intent);
    }
    else{
        Toast.makeText(getApplicationContext(), "device is not paired", 0).show();
    }

}

我还按以下方式填充设备

 receiver = new BroadcastReceiver(){
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();

            if(action.equals(BluetoothDevice.ACTION_FOUND)){
                Log.i("onReceive", "ACTION_FOUND");
                BluetoothDevice d = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                String s = "Not Paired";
                devices.add(d);
                for(int a = 0; a < pairedDevices.size(); a++){
                    if(d.getName().equals(pairedDevices.get(a).getName())){
                        //append 
                        s = "Paired";
                        break;
                    }
                }
                listAdapter.add(d.getName()+"("+s+")\n"+ d.getAddress());
            }

因此，设备列表必须已具有可分配的设备。我从以下代码获取null设备

public int onStartCommand(Intent intent, int flags, int startId) {
    Log.i(EXTRA_MESSAGE,"onStartCommand");


    BluetoothDevice selectedDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
    if(selectedDevice == null)
    {Log.i(EXTRA_MESSAGE,"null it is "); return -1;}
    connect = new ConnectThread(selectedDevice);
    connect.start();

Answer 1

改变这个：

BluetoothDevice selectedDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);

对此：

BluetoothDevice selectedDevice = intent.getParcelableExtra(EXTRA_MESSAGE);

将蓝牙设备传递给服务，null getParcelableExtra

1 个答案: