Question

我正在使用Java制作蓝牙应用程序。我创建了一个Devicelist活动来显示配对的所有设备和新发现的设备。当我从父活动打开此活动并单击某个设备时，MAC地址将从Devicelist发送到父活动，但是一旦我尝试从其中获取BluetoothDevice，我的应用程序崩溃（Logcat在下面）。

DeviceList.java

public static String EXTRA_DEVICE_ADDRESS = "device_address";

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

        // When discovery finds a device
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            // Get the BluetoothDevice object from the Intent
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            // If it's already paired, skip it, because it's been listed already
            if (device.getBondState() != BluetoothDevice.BOND_BONDED) {
                mNewDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
            }
        }
    }
}

private AdapterView.OnItemClickListener mDeviceClickListener = new AdapterView.OnItemClickListener() {
    public void onItemClick(AdapterView<?> av, View v, int arg2, long arg3) {
        // Cancel discovery because it's costly and we're about to connect
        mBtAdapter.cancelDiscovery();

        // Get the device MAC address, which is the last 17 chars in the View
        String info = ((TextView) v).getText().toString();
        String address = info.substring(info.length() - 17);

        // Create the result Intent and include the MAC address
        Intent data = new Intent();
        data.putExtra(EXTRA_DEVICE_ADDRESS, address);

        // Set result and finish(=close?) this Activity
        setResult(RESULT_OK, data);
        finish();
    }
};

TribotActivity（我的父类）

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_DEVICE_ADDRESS) {        // Check which request we're responding to. When doing more requests a switch case is probably a nicer way of doing this.
        if (resultCode == RESULT_OK) {                  // Make sure the request was successful
            if (data.hasExtra("device_address")) {
                Bundle bundleResult = data.getExtras(); // Store the Intent data(=device address) that we've received from the DeviceListActivity TODO Figure out why we can't simply use "String device = data.getStringExtra("device");"
                String address = bundleResult.getString("EXTRA_DEVICE_ADDRESS");
                //String address = data.getExtras().getString(DeviceListActivity.EXTRA_DEVICE_ADDRESS);
                BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);

                //BluetoothConnect.connect(device);

                textView = (TextView) findViewById(R.id.textView2);
                textView.setText("Device address: " + address);
            } else {
                Toast.makeText(getApplicationContext(), "Failed to get MAC address", Toast.LENGTH_SHORT).show();    //TODO Remove this when we've successfully sent through the address
            }
        } else {
            Toast.makeText(getApplicationContext(), "Failed to get MAC address", Toast.LENGTH_SHORT).show();    //TODO Remove this when we've successfully sent through the address
        }
    }
};

我从putExtra获取MAC地址。我甚至在textView上显示它以确保我得到正确的地址，但每次我尝试将蓝牙设备从中取出时，我的应用程序崩溃。

日志

04-04 12:12:50.638 10364-10364/com.hszuyd.noodle_.testing E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.hszuyd.noodle_.testing, PID: 10364
    Theme: themes:{}
    java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { (has extras) }} to activity {com.hszuyd.noodle_.testing/com.hszuyd.noodle_.testing.TribotActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.bluetooth.BluetoothDevice android.bluetooth.BluetoothAdapter.getRemoteDevice(java.lang.String)' on a null object reference
    at android.app.ActivityThread.deliverResults(ActivityThread.java:3733)
    at android.app.ActivityThread.handleSendResult(ActivityThread.java:3776)
    at android.app.ActivityThread.-wrap16(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1412)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5461)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
    at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:117)
    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.bluetooth.BluetoothDevice android.bluetooth.BluetoothAdapter.getRemoteDevice(java.lang.String)' on a null object reference
    at com.hszuyd.noodle_.testing.TribotActivity.onActivityResult(TribotActivity.java:88)
    at android.app.Activity.dispatchActivityResult(Activity.java:6456)
    at android.app.ActivityThread.deliverResults(ActivityThread.java:3729)
    at android.app.ActivityThread.handleSendResult(ActivityThread.java:3776)
    at android.app.ActivityThread.-wrap16(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1412)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5461)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
    at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:117)

我希望你们能帮助我！感谢。

Answer 1

初看： RuntimeException的：尝试将编辑TextView代码包装成：

    synchronized (this) {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                textView = (TextView) findViewById(R.id.textView2);
                textView.setText("Device address: " + address);
            }
        });
    }

NullPointerException：我不确定你的变种中是否有远程设备。在我的服务器端代码中，这有效：

        serverSocket = bluetoothAdapter.listenUsingRfcommWithServiceRecord(SERVICE_NAME, java.util.UUID.fromString(UUID));
        clientSocket = serverSocket.accept();
        if (clientSocket != null)
            clientDevice = clientSocket.getRemoteDevice(); //remember client

在客户端：

private final BroadcastReceiver discoveryStartedReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            // When discovery finds a device
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                // Get the BluetoothDevice object from the Intent
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                discoveredDevices.add(device);
                // Add the name and address to an array adapter to show in a ListView
                btDevicesAdapterList.add(device.getName() + "\n" + device.getAddress());

                //TODO
                if ((device.getName().equals(ROBOT_SERVER_NAME))){
                    if (clientState != CLIENT_CONNECTING) {
                        selectedServer = device;
                        Log.i(TAG, "SelectedServer: " + selectedServer.getName());
                        bluetoothAdapter.cancelDiscovery();
                        connectMethod();
                    }
                }
            }
        }
    };

getRemoteDevice给出错误

1 个答案: