在TabLayout中的片段之间滑动变慢

Question

我有一个使用viewpager设置TabLayout.viewpager设置了适配器.向适配器添加了11个片段,每个片段都有一个recyclerview.当我运行应用程序时,在片段之间滑动变慢.谁能告诉我这个问题的原因？

我的主要活动:

    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);
}

}

样本片段:

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

如果你有很多片段并希望在动画和交互中进行优化,那么你可以使用viewpager.setOffscreenPageLimit(int numberOfPages);

setOffscreenPageLimit()将具有默认值,1即viewpager将在其任一侧仅加载一个页面(片段),并且在滚动时将从适配器重新创建其他页面,因此它将基于页面将执行的操作而滞后.因此,当您知道页数时,使用此方法将有助于分页动画和交互的平滑性.

来自Doc setOffscreenPageLimit()

在空闲状态下设置应保留到视图层次结构中当前页面任一侧的页数.超出此限制的页面将在需要时从适配器重新创建.

这是作为优化提供的.如果您事先知道需要支持的页面数量或在页面上使用延迟加载机制,那么调整此设置可以获得分页动画和交互的感知平滑性.如果您有少量页面(3-4)可以一次保持活动状态,则用户来回切换时,新布局视图子树的布局花费的时间会更少