殺死時的片段被破壞

Question

我有一個有後臺線程更新進度條值，改變進度條繪製當進度值達到一定值時，我嘗試啓動onther片段的片段在後臺線程在相同的活動它的情況下這個錯誤

E/UncaughtException: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.support.v4.app.FragmentActivity.getResources()' on a null object reference 
    at com.example.mego.adas.ui.CarFragment$PotProgressThread$1.run(CarFragment.java:831) 
    at android.os.Handler.handleCallback(Handler.java:739) 
    at android.os.Handler.dispatchMessage(Handler.java:95) 
    at android.os.Looper.loop(Looper.java:148) 
    at android.app.ActivityThread.main(ActivityThread.java:7409) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) 
E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.mego.adas, PID: 25935 
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.support.v4.app.FragmentActivity.getResources()' on a null object reference 
    at com.example.mego.adas.ui.CarFragment$PotProgressThread$1.run(CarFragment.java:831) 
    at android.os.Handler.handleCallback(Handler.java:739) 
    at android.os.Handler.dispatchMessage(Handler.java:95) 
    at android.os.Looper.loop(Looper.java:148) 
    at android.app.ActivityThread.main(ActivityThread.java:7409) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) 

這裏是線程的代碼

class PotProgressThread implements Runnable { 

    @Override 
    public void run() { 
     while (potSensorValue <= 1025 && fragmentIsRunning) { 

      if (fragmentIsRunning) { 

       // Update the progress bar 
       potProgressBarHandler.post(new Runnable() { 
        public void run() { 
         potProgressBar.setProgress((int) potSensorValue); 
         if (potSensorValue >= 800) { 
          potProgressBar.setProgressDrawable(getActivity(). 
            getResources().getDrawable(R.drawable.progressbarred)); 
         } else { 
          potProgressBar.setProgressDrawable(getActivity(). 
            getResources().getDrawable(R.drawable.progressbarblue)); 

         } 
        } 
       }); 
       try { 
        Thread.sleep(50); 
       } catch (InterruptedException e) { 
        e.printStackTrace(); 
       } 
      } else { 
       break; 
      } 
     } 
    } 
} 

在這兒，我投我開始在onCreateView線程（）方法

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 


    View rootView = inflater.inflate(R.layout.fragment_car, container, false); 
    initializeScreen(rootView); 

    //check the internet connection 
    connectivityManager = (ConnectivityManager) getActivity().getSystemService(Context.CONNECTIVITY_SERVICE); 
    networkInfo = connectivityManager.getActiveNetworkInfo(); 

    if (networkInfo != null && networkInfo.isConnected()) { 
     buildGoogleApiClient(); 

     //set up the firebase 
     mFirebaseDatabase = FirebaseDatabase.getInstance(); 

     //get the references for the childes 
     //the main child for the directions services 
     carDatabaseReference = mFirebaseDatabase.getReference().child(constant.FIREBASE_CAR); 

     //the childes for the direction root 
     connectionStateDatabaseReference = mFirebaseDatabase.getReference() 
       .child(constant.FIREBASE_CAR).child(constant.FIREBASE_CONNECTION_STATE); 

     accidentStateDatabaseReference = mFirebaseDatabase.getReference() 
       .child(constant.FIREBASE_CAR).child(constant.FIREBASE_ACCIDENT_STATE); 

     startStateStateDatabaseReference = mFirebaseDatabase.getReference() 
       .child(constant.FIREBASE_CAR).child(constant.FIREBASE_START_STATE); 

     lightsStateDatabaseReference = mFirebaseDatabase.getReference() 
       .child(constant.FIREBASE_CAR).child(constant.FIREBASE_LIGHTS_STATE); 

     lockStateDatabaseReference = mFirebaseDatabase.getReference() 
       .child(constant.FIREBASE_CAR).child(constant.FIREBASE_LOCK_STATE); 

     mappingServicesDatabaseReference = mFirebaseDatabase.getReference() 
       .child(constant.FIREBASE_CAR).child(constant.FIREBASE_MAPPING_SERVICES); 

     sensorsValuesDatabaseReference = mFirebaseDatabase.getReference() 
       .child(constant.FIREBASE_CAR).child(constant.FIREBASE_SENSORES_VALUES); 

     connectionStateDatabaseReference.setValue(1); 


    } 
    //show Snackbar if there is no internet net connection 
    else { 
     if (carFragment != null) { 

      // Snackbar snackbar = Snackbar.make(carFragment, R.string.no_internet_connection, Snackbar.LENGTH_LONG); 
      // snackbar.show(); 
     } 
    } 

    //get the date from the connected thread 
    bluetoothHandler = new Handler() { 
     public void handleMessage(android.os.Message msg) { 
      //if message is what we want 
      if (msg.what == handlerState) { 
       // msg.arg1 = bytes from connect thread 
       String readMessage = (String) msg.obj; 

       //keep appending to string until ~ char 
       recDataString.append(readMessage); 

       //determine the end of the line 
       endOfLineIndex = recDataString.indexOf("~"); 
       if (fragmentIsRunning) { 
        refreshUI(); 
       } 

      } 
     } 
    }; 

    //setup ans start the threads 
    potThread = new Thread(new PotProgressThread()); 
    tempThread = new Thread(new TemperatureProgressThread()); 
    ldrThread = new Thread(new LdrProgressThread()); 


    fragmentIsRunning = true; 
    potThread.start(); 
    tempThread.start(); 
    ldrThread.start(); 


    //set the buttons listener 
    lightsButton.setOnClickListener(this); 
    lockButton.setOnClickListener(this); 
    disconnectButton.setOnClickListener(this); 
    startButton.setOnClickListener(this); 

    //setup the map fragment 
    MapFragment mapFragment = (MapFragment) getActivity().getFragmentManager().findFragmentById(R.id.my_location_fragment_car); 
    mapFragment.getMapAsync(this); 

    // Inflate the layout for this fragment 
    return rootView; 
} 

這裏是onDestoryview代碼（）方法

fragmentIsRunning = false; 
potThread.interrupt(); 

我怎樣才能殺死它

Answer 1

的Dalvik保持在運行的所有線程引用，這樣你的線程將繼續運行，除非它被終止或結束（一些reference）。因此，根據您開始線索的位置，您可能會創建多個線索。

在你的情況你的線程執行沒有完成，你改變片段讓你getActivity()將是無效的。

解決方法是在getActivity()之前，檢查isAdded()是否爲真，如果不是真，表示該片段已經分離，則調用getActivity()將返回null。

記得在線程中，在你調用getActivity()之前，你最好再次檢查isAdded（），因爲用戶可能在線程執行期間的任何時候退出活動。

其他的解決辦法

我不知道，但你可以通過實現初始化Context全球和你在你的線程上下文。

Context mContext; 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) 
{ 
    mContext = getActivity(); 
    .... 
} 

現在在您的線程中使用此上下文。

class PotProgressThread implements Runnable { 

    @Override 
    public void run() { 
     while (potSensorValue <= 1025 && fragmentIsRunning) { 

      if (fragmentIsRunning) { 

       // Update the progress bar 
       potProgressBarHandler.post(new Runnable() { 
        public void run() { 
         potProgressBar.setProgress((int) potSensorValue); 
         if (potSensorValue >= 800) { 
          potProgressBar.setProgressDrawable(mContext. 
            getResources().getDrawable(R.drawable.progressbarred)); 
         } else { 
          potProgressBar.setProgressDrawable(mContext. 
            getResources().getDrawable(R.drawable.progressbarblue)); 

         } 
        } 
       }); 
       try { 
        Thread.sleep(50); 
       } catch (InterruptedException e) { 
        e.printStackTrace(); 
       } 
      } else { 
       break; 
      } 
     } 
    } 
} 

我希望你能得到解決方案。