我可以从我的应用程序扫描蓝牙设备并列出扫描的设备。但我在配对设备时遇到问题。下面的代码是我在我的应用程序中使用的，
private void pairToBLE(BluetoothDevice device) {
// TODO Auto-generated method stub
try {
22. Method method = device.getClass().getMethod("createBond", (Class[]) null);
method.invoke(device, (Object[]) null);
} catch (NoSuchMethodException e) {
}
我在这里调用了上面的函数。
@Override
public boolean onContextItemSelected(MenuItem item) {
// TODO Auto-generated method stub
switch (item.getItemId()) {
case R.id.menu_connect:
pairToBLE(mBluetoothdevice);
break;
}
我注册了上下文菜单。在此之前，我能够扫描并列出 BT 设备，但每当我尝试配对时，它都会在第 22 行给出 NullPointerException。出现 NullpointerException 的原因是什么。完整代码在这里
public class AvailableDevices extends ListFragment {
String TAG = "com.example.tracker.AvailableDevices";
private LeDeviceListAdapter mLeDeviceListAdapter;
private Handler mHandler;
private boolean mScanning;
Context context;
public BluetoothDevice mBluetoothdevice;
// Stops scanning after 10 seconds.
private static final long SCAN_PERIOD = 10000;
BLEService mBLEService;
private String mDeviceAddrees;
private String mDeviceName;
@Override
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
Log.i(TAG, "inside onActivityCreated");
context = AvailableDevices.this.getActivity();
mLeDeviceListAdapter = new LeDeviceListAdapter();
//System.out.println("value of adapter=="+mLeDeviceListAdapter.getCount());
setListAdapter(mLeDeviceListAdapter);
scanLeDevice(true);
registerForContextMenu(getListView());
}
public class LeDeviceListAdapter extends BaseAdapter{
private ArrayList<BluetoothDevice> mLeDevices;
private LayoutInflater mInflator;
Bundle savedInstanceState;
public LeDeviceListAdapter() {
// TODO Auto-generated constructor stub
super();
Log.i(TAG, "inside LeDeviceListAdapter");
mLeDevices = new ArrayList<BluetoothDevice>();
mInflator = AvailableDevices.this.getLayoutInflater(null);
}
public void addDevices(BluetoothDevice device){
if(!mLeDevices.contains(device)){
mLeDevices.add(device);
System.out.println("device added++++++++++"+mLeDevices.add(device));
}
}
public BluetoothDevice getDevice(int position){
return mLeDevices.get(position);
}
public void clear(){
mLeDevices.clear();
}
@Override
public int getCount() {
// TODO Auto-generated method stub
int count = mLeDevices.size();
System.out.println("device counted++++++++++"+count);
return count;
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return mLeDevices.get(position);
}
@Override
public long getItemId(int i) {
// TODO Auto-generated method stub
System.out.println("device getItemId++++++++++"+i);
return i;
}
@Override
public View getView(int position, View view, ViewGroup parent) {
// TODO Auto-generated method stub
ViewHolder viewHolder;
Log.i(TAG, "inside getView===>");
if(view == null){
view = mInflator.inflate(R.layout.avldev_frag, null);
viewHolder = new ViewHolder();
viewHolder.deviceAdress = (TextView)view.findViewById(R.id.device_address);
viewHolder.deviceName = (TextView)view.findViewById(R.id.device_name);
view.setTag(viewHolder);
}else{
viewHolder = (ViewHolder)view.getTag();
Log.i(TAG, "inside ViewHolder===>"+viewHolder);
}
BluetoothDevice device = mLeDevices.get(position);
final String deviceName = device.getName();
if (deviceName != null && deviceName.length() > 0){
Log.i(TAG, "inside if*****");
viewHolder.deviceName.setText(deviceName);
viewHolder.deviceAdress.setText(device.getAddress());
Log.i(TAG, "bounded devices*****===>"+BluetoothDevice.BOND_BONDED);
}else{
viewHolder.deviceName.setText(R.string.unknown_device);
}
Log.i(TAG, "device name my app*****===>"+deviceName);
return view;
}
}
static class ViewHolder{
TextView deviceAdress;
TextView deviceName;
}
// Device scan callback.
private BluetoothAdapter.LeScanCallback mLeScanCallback =
new BluetoothAdapter.LeScanCallback() {
@Override
public void onLeScan(final BluetoothDevice device, int rssi,
byte[] scanRecord) {
// TODO Auto-generated method stub
getActivity().runOnUiThread(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
mLeDeviceListAdapter.addDevices(device);
mLeDeviceListAdapter.notifyDataSetChanged();
}
});
}
};
// Device scan callback.
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;
MainActivity.mBluetoothAdapter.stopLeScan(mLeScanCallback);
//invalidateOptionsMenu();
}
}, SCAN_PERIOD);*/
Log.d(TAG, "inside scanLeDevice function****");
mScanning = true;
System.out.println("value of mBluetoothAdapter+++++++++++++++=="
+MainActivity.mBluetoothAdapter.getName().toString());
MainActivity.mBluetoothAdapter.startLeScan(mLeScanCallback);
Log.d(TAG, "after start****");
} else {
mScanning = false;
MainActivity.mBluetoothAdapter.stopLeScan(mLeScanCallback);
}
//invalidateOptionsMenu();
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v,
ContextMenuInfo menuInfo) {
// TODO Auto-generated method stub
super.onCreateContextMenu(menu, v, menuInfo);
menu.add(Menu.NONE, R.id.menu_connect, Menu.NONE, "Connect");
menu.add(Menu.NONE, R.id.menu_disconnect, Menu.NONE, "Disconnect");
}
@Override
public boolean onContextItemSelected(MenuItem item) {
// TODO Auto-generated method stub
switch (item.getItemId()) {
case R.id.menu_connect:
Log.d(TAG,"INSIDE MENU");
ConnectDevices();
if(mBluetoothdevice == null){
Log.d(TAG, "inside mBluetoothdevice null *****");
}else{
Log.d(TAG, "inside mBluetoothdevice not null *****");
pairToBLE(mBluetoothdevice);
}
break;
case R.id.menu_disconnect :
default:
break;
}
return super.onContextItemSelected(item);
}
private void ConnectDevices(){
int position = 0;
final BluetoothDevice device = mLeDeviceListAdapter.getDevice(position);
mDeviceAddrees = device.getAddress();
MainActivity.mBLEService.connect(mDeviceAddrees);
}
private void pairToBLE(BluetoothDevice device) {
// TODO Auto-generated method stub
try {
Log.d(TAG, "inside pairToBLE");
Method method = device.getClass().getMethod("createBond", (Class[]) null);
method.invoke(device, (Object[]) null);
Log.d(TAG, "inside pairToBLE after *****");
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void onDestroyView() {
// TODO Auto-generated method stub
super.onDestroyView();
scanLeDevice(false);
}
}
谢谢
最佳答案
很可能device为空。当您调用pairToBLE时，您确定mBluetoothdevice不为空吗？添加一个 Log 语句来查看它是什么。
关于java - 配对蓝牙设备时出现 NullPointerException，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/26609861/