Fragment被replace後視圖被摧毀

在Fragment被replace後再返回,視圖變成了空白

最近在做項目時，發現Fragment在被replace後再返回(在已經addToBackStack的情況下)，原來的Fragment視圖變成一片空白。

測試:

• Fragment一共有11個生命週期，我把Fragment的生命週期過程全都打一遍Log

  public class fragment1 extends Fragment {
  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.aaaa, container, false);
    Log.d("fragmentLife", "onCreateView");
      return view;
  }
  
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Log.d("fragmentLife", "onCreate");
  }
  
  @Override
  public void onAttach(Activity activity) {
    Log.d("fragmentLife", "onAttach");
    super.onAttach(activity);
  }
  
  @Override
  public void onActivityCreated(Bundle savedInstanceState) {
    Log.d("fragmentLife", "onActivityCreated");
    super.onActivityCreated(savedInstanceState);
  }
  
  @Override
  public void onStart() {
    Log.d("fragmentLife", "onStart");
    super.onStart();
  }
  
  @Override
  public void onResume() {
    Log.d("fragmentLife", "onResume");
    super.onResume();
  }
  
  @Override
  public void onPause() {
    Log.d("fragmentLife", "onPause");
    super.onPause();
  }
  
  @Override
  public void onStop() {
    Log.d("fragmentLife", "onStop");
    super.onStop();
  }
  
  @Override
  public void onDestroy() {
    Log.d("fragmentLife", "onDestroy");
    super.onDestroy();
  }
  
    @Override
    public void onDestroyView() {
    Log.d("fragmentLife", "onDestroyView");
    super.onDestroyView();
  }
  
  @Override
  public void onDetach() {
    Log.d("fragmentLife", "onDetach");
    super.onDetach();
  }
  ｝ 
  

• 然後在Activity中先add再replace,然後再返回，最後退出

  int i = 0;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  
    Log.d("fragmentLife", "添加");
    getFragmentManager().beginTransaction()
    .add(R.id.container, new fragment1())
    .commit();
  
    Button button = (Button)findViewById(R.id.button1);
    button.setOnClickListener(new OnClickListener() {
      @Override
      public void onClick(View v) {
          Log.d("fragmentLife", "替換");
          getFragmentManager().beginTransaction()
          .replace(R.id.container, new fragment2())
          .addToBackStack(null)
          .commit();  
      }
  });
  }
  
  @Override
  public void onBackPressed() {
      i++;
  if(i==1){
      Log.d("fragmentLife", "返回");
  }else{
    Log.d("fragmentLife", "退出程序");
      }
    super.onBackPressed();
  }
  

• 我們來看一下Log日誌

  D/fragmentLife(2440): 添加
  D/fragmentLife(2440): onAttach
  D/fragmentLife(2440): onCreate
  D/fragmentLife(2440): onCreateView
  D/fragmentLife(2440): onActivityCreated
  D/fragmentLife(2440): onStart
  D/fragmentLife(2440): onResume
  D/fragmentLife(2440): 替換
  D/fragmentLife(2440): onPause
  D/fragmentLife(2440): onStop
  D/fragmentLife(2440): onDestroyView
  D/fragmentLife(2440): 返回
  D/fragmentLife(2440): onCreateView
  D/fragmentLife(2440): onActivityCreated
  D/fragmentLife(2440): onStart
  D/fragmentLife(2440): onResume
  D/fragmentLife(2440): 退出程序
  D/fragmentLife(2440): onPause
  D/fragmentLife(2440): onStop
  D/fragmentLife(2440): onDestroyView
  D/fragmentLife(2440): onDestroy
  D/fragmentLife(2440): onDetach
  

看出問題: Fragment已經addToBackStack,在被replace後,雖然Fragment實例沒有被摧毀，但是會回調onDestroyView()方法，導致視圖被摧毀。

解決方法: 定義一個boolean變量，在onCreateView方法中判斷此boolean的值，決定是否恢復視圖。

• 1.定義一個boolean變量

  private boolean isViewDetroy;
  

• 2.在onCreate方法中初始化isViewDetroy = false;

  @Override
  public void onCreate(@Nullable Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      returView = false;
  }
  

• 3.在Fragment的onDestroyView方法中讓isViewDetroy = true;

  @Override
  public void onDestroyView() {
     super.onDestroyView();
     isViewDetroy = true;
  }
  

• 4.在onCreatView方法中判斷isViewDetroy,如果爲true,則恢復視圖

  @Override
  public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
      View view = inflater.inflate(R.layout.fragmen,container,false);
  
     if(isViewDetroy = true){
         ......  //此處執行恢復視圖操作
      }
      return view;
  }
  

謝謝！