android - 在 TabLayout 中的 fragment 之间滑动变慢

Question

我有一个 TabLayout 是用 viewpager 设置的。 viewpager 是用适配器设置的。适配器中添加了 11 个 fragment ，每个 fragment 都有一个 recyclerview。当我运行应用程序时，在 fragment 之间滑动会变慢。谁能告诉我这个问题的原因？

我的主要 Activity :

    myTabLayout.setTabMode(TabLayout.MODE_SCROLLABLE);


    mainViewPager = (ViewPager) findViewById(R.id.mainViewPager);
    tabLayoutAdapter = new TabLayoutAdapter(getSupportFragmentManager());
    tabLayoutAdapter.addFragment(new HomeFragment());
    tabLayoutAdapter.addFragment(new ClipFragment());
    tabLayoutAdapter.addFragment(new MovieFragment());
    tabLayoutAdapter.addFragment(new SerialFragment());
    tabLayoutAdapter.addFragment(new MusicFragment());
    tabLayoutAdapter.addFragment(new BookFragment());
    tabLayoutAdapter.addFragment(new PixFragment());
    tabLayoutAdapter.addFragment(new GameFragment());
    tabLayoutAdapter.addFragment(new NewsFragment());
    tabLayoutAdapter.addFragment(new LiveFragment());
    tabLayoutAdapter.addFragment(new AdvancedSearchFragment());
    mainViewPager.setAdapter(tabLayoutAdapter);
    myTabLayout.setupWithViewPager(mainViewPager);

我的适配器:

public class TabLayoutAdapter extends FragmentStatePagerAdapter {
List<Fragment> tabPages = new ArrayList<>();

public TabLayoutAdapter(FragmentManager fm) {
    super(fm);
}

@Override
public Fragment getItem(int position) {
    return tabPages.get(position);
}

@Override
public int getCount() {
    return tabPages.size();
}

public void addFragment(Fragment page){
    tabPages.add(page);
}

示例 fragment :

public class MovieFragment extends Fragment {
RecyclerView movieRecyclerView;
List<Movie> movieList;
MovieAdapter movieAdapter;
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Log.d("Fragment", "thread = " + Thread.currentThread().getName());
    Log.i("Fragment", "thread = " + Thread.currentThread().getName());
}


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


    View movieView = inflater.inflate(R.layout.tab_movie, container, false);
    return movieView;
}


@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    movieRecyclerView = (RecyclerView) view.findViewById(R.id.movieRecyclerView);
    movieList = new ArrayList<Movie>();
    movieAdapter = new MovieAdapter(view.getContext(), movieList);

    RecyclerView.LayoutManager mLayoutManager = new GridLayoutManager(view.getContext(), 2);
    movieRecyclerView.setLayoutManager(mLayoutManager);
    movieRecyclerView.addItemDecoration(new GridSpacingItemDecoration(2, dpToPx(10), false));
    movieRecyclerView.setItemAnimator(new DefaultItemAnimator());
    movieRecyclerView.setAdapter(movieAdapter);

    prepareMovies();



}

public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

    private int spanCount;
    private int spacing;
    private boolean includeEdge;

    public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {
        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view); // item position
        int column = position % spanCount; // item column

        if (includeEdge) {
            outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
            outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

            if (position < spanCount) { // top edge
                outRect.top = spacing;
            }
            outRect.bottom = spacing; // item bottom
        } else {
            outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
            outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
            if (position >= spanCount) {
                outRect.top = spacing; // item top
            }
        }
    }
}



private void prepareMovies() {
    int[] covers = new int[]{
            R.drawable.bossbaby,
            R.drawable.abeautifulmind,
            R.drawable.despicableme,
            R.drawable.harrypotter,
            R.drawable.thegodfather,
            R.drawable.piratesofcaribbean,
            };

    Movie movie = new Movie("Boss Baby",10000,4.5,20000,16000, covers[0]);
    movieList.add(movie);
    movie = new Movie("A Beautiful mind",35100,4.9,40000,39000, covers[1]);
    movieList.add(movie);
    movie = new Movie("Despicable me",20000,4.7,33000,31000, covers[2]);
    movieList.add(movie);
    movie = new Movie("Harry Potter",90000,5.0,110000,105000, covers[3]);
    movieList.add(movie);
    movie = new Movie("The God Father",70000,4.9,90000,86700, covers[4]);
    movieList.add(movie);
    movie = new Movie("Pirates of caribbean",50000,4.6,70000,64000, covers[5]);
    movieList.add(movie);



    movieAdapter.notifyDataSetChanged();
}

private int dpToPx(int dp) {
    Resources r = getResources();
    return Math.round(TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, r.getDisplayMetrics()));
}

Answer 1

当你的fragment比较多，想对其动画和交互进行优化，可以使用viewpager.setOffscreenPageLimit(int numberOfPages);

setOffscreenPageLimit() 将具有默认值 1 即 viewpager 将仅在其任一侧加载一个页面( fragment )，滚动时将从适配器重新创建其他页面因此它会根据页面将执行的操作而滞后。因此，当您知道页面数量时，使用此方法将有助于页面动画和交互的流畅性。

来自文档 setOffscreenPageLimit()

Set the number of pages that should be retained to either side of the current page in the view hierarchy in an idle state. Pages beyond this limit will be recreated from the adapter when needed.

这是作为优化提供的。如果你事先知道号码 您需要支持或具有延迟加载机制的页面 放置在您的页面上，调整此设置可以带来好处 分页动画和交互的感知流畅度。如果你有 您可以同时保持 Activity 状态的少量页面 (3-4)， 新创建的 View 子树的布局将花费更少的时间，因为 用户页面来回