得到錯誤

我做掃描附近的藍牙設備的任務，但我不知道它在哪裏得到的錯誤，因爲有時它運行順利，但有時它這裏得到錯誤

09-09 16:46:49.574 5577-5577/? E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: aiyaz.conceptioni.ticket, PID: 5577 
    java.lang.NullPointerException 
      at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394) 
      at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362) 
      at android.widget.AbsListView.obtainView(AbsListView.java:2341) 
      at android.widget.ListView.measureHeightOfChildren(ListView.java:1273) 
      at android.widget.ListView.onMeasure(ListView.java:1182) 
      at android.view.View.measure(View.java:16845) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374) 
      at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1621) 
      at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1199) 
      at android.widget.LinearLayout.onMeasure(LinearLayout.java:609) 
      at android.view.View.measure(View.java:16845) 
      at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:824) 
      at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:500) 
      at android.view.View.measure(View.java:16845) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374) 
      at android.widget.FrameLayout.onMeasure(FrameLayout.java:340) 
      at android.view.View.measure(View.java:16845) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374) 
      at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1621) 
      at android.widget.LinearLayout.measureVertical(LinearLayout.java:742) 
      at android.widget.LinearLayout.onMeasure(LinearLayout.java:607) 
      at android.view.View.measure(View.java:16845) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374) 
      at android.widget.FrameLayout.onMeasure(FrameLayout.java:340) 
      at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2368) 
      at android.view.View.measure(View.java:16845) 
      at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2289) 
      at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1355) 
      at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1552) 
      at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1232) 
      at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6271) 
      at android.view.Choreographer$CallbackRecord.run(Choreographer.java:788) 
      at android.view.Choreographer.doCallbacks(Choreographer.java:591) 
      at android.view.Choreographer.doFrame(Choreographer.java:560) 
      at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:774) 
      at android.os.Handler.handleCallback(Handler.java:808) 
      at android.os.Handler.dispatchMessage(Handler.java:103) 
      at android.os.Looper.loop(Looper.java:193) 
      at android.app.ActivityThread.main(ActivityThread.java:5347) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:515) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:835) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:651) 
      at dalvik.system.NativeStart.main(Native Method)

我不顯示給錯誤不知道它在哪裏得到NullPointerException。我一直在尋找整天，但找不到它。這是我的代碼

public class AppSettings extends Activity { 

    Button btnLogout; 
    ImageView imgBlutoothOnOff,homeIcon; 
    boolean isBluetoothOn; 
    BluetoothAdapter bluetoothAdapter; 
    DatabaseHelper databaseHelper; 
    SQLiteDatabase sqLiteDatabase; 
    SharedPreferences sharedPreferences; 
    ListView bluetoothDeviceList; 
    ArrayList<String> bluetoothDeviceName=new ArrayList<>(); 
    ArrayList<String> bluetoothDeviceId=new ArrayList<>(); 
    ArrayAdapter<String> arrayAdapter; 
    BluetoothDevices getBluetoothDevices; 
    CustomProgressDialog customProgressDialog; 
    private BroadcastReceiver broadcastReceiver; 

@Override 
    protected void onCreate(Bundle savedInstance){ 
     super.onCreate(savedInstance); 
     setContentView(R.layout.activity_app_settings); 
     getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON); 
     bluetoothAdapter=BluetoothAdapter.getDefaultAdapter(); 
     registerReceiver(mReceiver, new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED)); 

    initialize(); 

    imgBlutoothOnOff.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      if(isBluetoothOn){ 
       bluetoothAdapter.disable(); 
       isBluetoothOn=false; 
       imgBlutoothOnOff.setImageResource(R.drawable.bluetooth_key_off); 
      }else{ 
       bluetoothAdapter.enable(); 
       isBluetoothOn=true; 
       imgBlutoothOnOff.setImageResource(R.drawable.bluetooth_key_on); 
      } 
     } 
    }); 


} 
public void initialize(){ 
    btnLogout=(Button)findViewById(R.id.setting_logout_btn); 
    imgBlutoothOnOff=(ImageView)findViewById(R.id.settings_bluetooth_on_off); 
    databaseHelper=new DatabaseHelper(AppSettings.this); 
    sqLiteDatabase=databaseHelper.getWritableDatabase(); 
    sharedPreferences=getSharedPreferences(ReferenceStrings.SharedPref,MODE_PRIVATE); 

customProgressDialog=new CustomProgressDialog(AppSettings.this); 
    customProgressDialog.setCancelable(true); 


    bluetoothDeviceList=(ListView)findViewById(R.id.app_settings_bluetooth_list); 
    if(bluetoothAdapter.isEnabled()){ 
     isBluetoothOn=true; 
     imgBlutoothOnOff.setImageResource(R.drawable.bluetooth_key_on); 
     IntentFilter filter = new IntentFilter(); 
     filter.addAction(BluetoothDevice.ACTION_FOUND); 
     filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_STARTED); 
     filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED); 
     this.registerReceiver(mReceiver_search, filter); 
     startDiscovery(); 
    } 
    else { 
     isBluetoothOn = false; 
     imgBlutoothOnOff.setImageResource(R.drawable.bluetooth_key_off); 
    } 

} 

private void getPairedDevices(){ 

    BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); 
    Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices(); 

    List<String> s = new ArrayList<String>(); 

    for(BluetoothDevice bt : pairedDevices) { 
     s.add(bt.getName()); 
    } 
    startDiscovery(); 
} 


private void startDiscovery(){ 
    arrayAdapter=new ArrayAdapter<String>(getBaseContext(),android.R.layout.simple_list_item_1,bluetoothDeviceName); 
    arrayAdapter.setNotifyOnChange(true); 
    bluetoothDeviceList.setAdapter(arrayAdapter); 
    bluetoothAdapter.startDiscovery(); 
} 

private final BroadcastReceiver mReceiver = new BroadcastReceiver() { 
    public void onReceive (Context context, Intent intent) { 
     String action = intent.getAction(); 
     if (action.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) { 
      final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, 
        BluetoothAdapter.ERROR); 
      switch (state) { 
       case BluetoothAdapter.STATE_OFF: 
        arrayAdapter.clear(); 
        arrayAdapter.notifyDataSetChanged(); 
        Toast.makeText(context, "Bluetooth is off", Toast.LENGTH_LONG).show(); 
        break; 
       case BluetoothAdapter.STATE_TURNING_OFF: 
        break; 
       case BluetoothAdapter.STATE_ON: 
        Toast.makeText(context, "Bluetooth is on", Toast.LENGTH_LONG).show(); 
        startDiscovery(); 
        break; 
       case BluetoothAdapter.STATE_TURNING_ON: 
        break; 
      } 
     } 
    } 
}; 

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

     if (BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action)) { 
       customProgressDialog.show(); 
     } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) { 
      customProgressDialog.cancel(); 

     } else if (BluetoothDevice.ACTION_FOUND.equals(action)) { 
      //bluetooth device found 

    BluetoothDevice device = (BluetoothDevice) intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); 
      bluetoothDeviceName.add(device.getName()); 
      bluetoothDeviceId.add(device.getAddress()); 
      arrayAdapter.notifyDataSetChanged(); 
     } 
    } 
}; 

@Override 
protected void onPause() { 
    super.onPause(); 
    try { 
     if(mReceiver!=null) { 
      unregisterReceiver(mReceiver); 
     } 
    }catch (Exception e){ 

    } 
} 
}

請忽略未使用的變量。讓我知道我做錯了什麼。謝謝。 :)

來源

2015-09-09 Aiyaz Parmar