Question

在Android应用程序中，我有多个片段，在片段之一（片段A）中，我使用布尔变量在按钮单击的GridView中切换两组图像。 GridView项目点击导致第二个片段（片段B）。按下片段B上的“返回”按钮时，片段A中的网格视图将加载默认的图像集，而不是在进入下一个片段片段B之前设置的图像。

请指导如何恢复上一组图像而不是默认的图像组？

在MainActivity中，我在BackPressed上实现了这样：

@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();
    }

GridViewFragment.java的OnCreate方法

@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;

    }

Answer 1

您应该在setRetainInstance(true)片段方法中调用onCreate，或者在onSaveInstanceState和onRetainInstanceState

中保存并加载正确的值编辑：我通常做这样的事情：

@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;
}

在后退按钮上获取Android片段的先前状态

1 个答案: