代码之家 › 专栏 › 技术社区 › Ssubrat Rrudra

Logcat显示Parcelabe值不为空,但调用LayoutManager 35; OnRestoreInstanceState不会重定向到保存状态

recyclerview-layout recycler-adapter google-cloud-firestore android-recyclerview android

Ssubrat Rrudra · 技术社区 · 5 年前

正在GroceryFragment中保存onPause()处的RecyclerView状态:

@Override
public void onPause() {
    super.onPause();
    Log.d(TAG, "onPause: called");
    FragmentStateListener fragmentStateListener = (FragmentStateListener) getActivity();
    fragmentStateListener.savingFragmentState(mCategoriesRV.getLayoutManager().onSaveInstanceState(), GROCERY_FRAGMENT);
    Log.d(TAG, "onPause: state - " + mCategoriesRV.getLayoutManager().onSaveInstanceState());
}

下面是接口fragmentStateListener:

public interface FragmentStateListener {

public void savingFragmentState(Parcelable parcelable, int fragmentInt);

}

此接口正在由HomeActivity实现:

@Override
public void savingFragmentState(Parcelable parcelable, int fragmentInt) {
    Log.d(TAG, "savingFragmentState: parcelable = " + parcelable);
    Log.d(TAG, "savingFragmentState: fragmentInt = " + fragmentInt);
    switch (fragmentInt) {
        case HomeFragment.HOME_FRAGMENT:
            mHomeFragmentSavedState = parcelable;
            break;
        case GroceryFragment.GROCERY_FRAGMENT:
            mGroceryFragmentSavedState = parcelable;
            break;
    }
}

而且由于GroceryFragment是BrowseFragment中嵌套的ViewPager片段,因此首先将此Parcelable值传输到BrowseFragment,然后从那里传输到GroceryFragment:

 case R.id.browse_menu_item :
                                Log.d(TAG, "onNavigationItemSelected: browse icon clicked");

                                mBottomNavigationViewBNV.enableShiftingMode(1, false);
                                toggleChangeBottomNavigationItemIconsColor (1, 0, 2, 3, 4);
                                replaceFragment(BrowseFragment.newInstance(null, null, mGroceryFragmentSavedState), R.id.fragments_container_CL);
                                break;

...
fragmentList.add(GroceryFragment.newInstance(null, null, mGroceryFragmentSavedState));

以下是GroceryFragment中的newInstance方法:

 public static GroceryFragment newInstance(String param1, String param2, Parcelable savedState) {
    GroceryFragment fragment = new GroceryFragment();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    args.putString(ARG_PARAM2, param2);
    args.putParcelable(RECYCLERVIEW_STATE, savedState);
    Log.d(TAG, "newInstance: savedstate = " + savedState);
    fragment.setArguments(args);
    return fragment;
}

GroceryFragment的onCreate()方法:

 @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (getArguments() != null) {
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
        mSavedState = getArguments().getParcelable(RECYCLERVIEW_STATE);
    }
}

最后将savedstate还原到recyclerview的layoutmanager:

mCategoriesRV.setHasFixedSize(true);
        CategoriesRecyclerAdapter categoriesRecyclerAdapter =
                new CategoriesRecyclerAdapter(getFirestoreRecyclerOptions (), getActivity(), GroceryFragment.this, mCategoriesCL);
        mCategoriesRV.setAdapter(categoriesRecyclerAdapter);
    categoriesRecyclerAdapter.startListening();
    mCategoriesRV.setLayoutManager(new GridLayoutManager(getActivity(), 2));
    if(mSavedState != null) {
        Log.d(TAG, "mCategoriesRVAction: mSavedState = " + mSavedState);
        mCategoriesRV.getLayoutManager().onRestoreInstanceState(mSavedState);
    }

上述代码的logcat屏幕截图,其中清楚地显示msavedstate不是空的,但它仍在恢复状态:

0 回复 | 直到 5 年前