获取“返回”按钮上Android片段的先前状态

在android应用程序中，我有多个片段，在其中一个片段（片段A）中，我使用布尔变量在GridView中的两组图像之间切换。第四个GridView项单击将导致第二个片段（片段B）。按片段B上的后退按钮时，片段A中的gridview将加载默认的图像集，而不是在继续下一个片段B之前加载的图像集

请指导如何恢复以前的图像集而不是默认图像集

在MainActivity中，我在BackPressed上实现了如下内容：

@Override
    public void onBackPressed() {
        if (frag instanceof SettingsFragment)
            loadGridViewFragment();
        else if (frag instanceof SingleDuaViewPagerFragment) {
            boolean keyIsFavSel = new SharedPreferencesSupplication().read(SingletonClass.keyIsFavSelected, false);
            if (keyIsFavSel)
                loadDuasListFragment();
            else
                loadGridViewFragment();
        }
        else if (frag instanceof DuasListFragment) {
            boolean keyIsFavSel = new SharedPreferencesSupplication().read(SingletonClass.keyIsFavSelected, false);
            if (keyIsFavSel)
                loadGridViewFragment();
            else
                loadSingleDuaFragment();
        }
        else
            super.onBackPressed();
    }

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setRetainInstance(true);
}

private View view;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    if (view == null) {
        context = inflater.getContext();
        view = inflater.inflate(R.layout.fragment_gridview, container, false); 
        ga = new GridViewAdapter(context);
        Btn_lang_Ch = (Button) view.findViewById(R.id.lng_ch);
        Btn_Settings = (Button) view.findViewById(R.id.button_settings);
        favoriteDuas = (Button) view.findViewById(R.id.btn_favorite_duas);
        GridMenu =(GridView) view.findViewById(R.id.gridView1);
        float scalefactor = getResources().getDisplayMetrics().density * 150;
        @SuppressWarnings("deprecation")
        int number = getActivity().getWindowManager().getDefaultDisplay().getWidth();
        int columns = (int) ((float) number / (float) scalefactor);
        GridMenu.setAdapter(ga);
        GridMenu.setNumColumns(columns);
    }
    else {
       // remove view from previously attached ViewGroup
       ViewGroup parent = (ViewGroup) view.getParent();
       parent.removeView(view);
    }    
    return view;
}

OnCreate方法的GridViewFragment.java

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    //  fragment = new GridViewFragment();
        context = inflater.getContext();
        View view = inflater.inflate(R.layout.fragment_gridview, container, false); 
        ga = new GridViewAdapter(context);
        Btn_lang_Ch = (Button) view.findViewById(R.id.lng_ch);
        Btn_Settings = (Button) view.findViewById(R.id.button_settings);
        favoriteDuas = (Button) view.findViewById(R.id.btn_favorite_duas);
        GridMenu =(GridView) view.findViewById(R.id.gridView1);
    float scalefactor = getResources().getDisplayMetrics().density * 150;
        @SuppressWarnings("deprecation")
        int number = getActivity().getWindowManager().getDefaultDisplay().getWidth();
        int columns = (int) ((float) number / (float) scalefactor);
        GridMenu.setAdapter(ga);
        GridMenu.setNumColumns(columns);    
        setRetainInstance(true);
        return view;

    }

---

您应该在

onCreate

fragment方法中调用

setRetainInstance（true）

，或者在

onSaveInstanceState

和

onRetainInstanceState

编辑：我通常会这样做：

@Override
    public void onBackPressed() {
        if (frag instanceof SettingsFragment)
            loadGridViewFragment();
        else if (frag instanceof SingleDuaViewPagerFragment) {
            boolean keyIsFavSel = new SharedPreferencesSupplication().read(SingletonClass.keyIsFavSelected, false);
            if (keyIsFavSel)
                loadDuasListFragment();
            else
                loadGridViewFragment();
        }
        else if (frag instanceof DuasListFragment) {
            boolean keyIsFavSel = new SharedPreferencesSupplication().read(SingletonClass.keyIsFavSelected, false);
            if (keyIsFavSel)
                loadGridViewFragment();
            else
                loadSingleDuaFragment();
        }
        else
            super.onBackPressed();
    }

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setRetainInstance(true);
}

private View view;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    if (view == null) {
        context = inflater.getContext();
        view = inflater.inflate(R.layout.fragment_gridview, container, false); 
        ga = new GridViewAdapter(context);
        Btn_lang_Ch = (Button) view.findViewById(R.id.lng_ch);
        Btn_Settings = (Button) view.findViewById(R.id.button_settings);
        favoriteDuas = (Button) view.findViewById(R.id.btn_favorite_duas);
        GridMenu =(GridView) view.findViewById(R.id.gridView1);
        float scalefactor = getResources().getDisplayMetrics().density * 150;
        @SuppressWarnings("deprecation")
        int number = getActivity().getWindowManager().getDefaultDisplay().getWidth();
        int columns = (int) ((float) number / (float) scalefactor);
        GridMenu.setAdapter(ga);
        GridMenu.setNumColumns(columns);
    }
    else {
       // remove view from previously attached ViewGroup
       ViewGroup parent = (ViewGroup) view.getParent();
       parent.removeView(view);
    }    
    return view;
}

---

我在OnCreate中调用了setRetainInstance（true），但仍在加载默认图像。应该保存哪些值？请解释一下。若你们调用了setRetainInstanceState（true），那个么当你们回到前面的片段时，只调用了onCreateView。。。这意味着您应该在onCreateView中返回现有视图。如果它不为null，我通常只从其父视图中删除视图并返回视图的现有实例。在onCreateView中创建视图时，将视图保存到全局变量，如果存在，则返回现有变量。如果在onCreateView中调用setRetainInstanceState，而不是在onCreateOnCreateView中调用setRetainInstanceState，则所有组件都要绘制UI，那么在OnCreate中应该做什么？感谢您的帮助，但仍然没有区别。