TabLayout 中的片段仅在用户滑动 Android 时加载

Fragment in TabLayout only load when user slide Android(TabLayout 中的片段仅在用户滑动 Android 时加载)

问题描述

您好，我正在使用 tablayout 和 viewpagerfragment 和少数子 fragment 的应用程序>.问题是我所有的孩子 fragment(来自 Tablayout)总是执行(每当用户单击父 fragment 时加载所有代码.如何获取子 fragment 仅在用户滑动到它时加载(例如，我有 2 个选项卡，选项卡 2 中的内容仅在用户滑动到选项卡 2 时加载)

Hi I'm making an app with A fragment and few child fragment inside it using tablayout and viewpager. The problem is all my child fragment (from Tablayout) always execute (load all the code inside whenever user click the parent fragment. How to get the child fragment only load whenever the the user slide to it (for example I have 2 tab, content in tab 2 only load when user slide to tab 2)

这是我的父片段代码

public class ManageEventFragment extends Fragment {


    public ManageEventFragment() {
        // Required empty public constructor
    }


    TabLayout tabLayout;
    ViewPager viewPager;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View viewFragment = inflater.inflate(R.layout.fragment_manage_event, container, false);

        viewPager = (ViewPager) viewFragment.findViewById(R.id.viewPager);

        tabLayout = (TabLayout) viewFragment.findViewById(R.id.tabLayout);

        viewPager.setAdapter(new CustomAdapter(getChildFragmentManager(), getContext()));
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));

        return viewFragment;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {

        //        tabLayout.setupWithViewPager(viewPager);
        tabLayout.post(new Runnable() {
            @Override
            public void run() {
                tabLayout.setupWithViewPager(viewPager);
            }
        });

        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
            }
        });

        if (ViewCompat.isLaidOut(tabLayout)) {
            tabLayout.setupWithViewPager(viewPager);
        } else {
            tabLayout.addOnLayoutChangeListener(new View.OnLayoutChangeListener() {
                @Override
                public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
                    tabLayout.setupWithViewPager(viewPager);
                    tabLayout.removeOnLayoutChangeListener(this);
                }
            });
        }

        super.onActivityCreated(savedInstanceState);

    }


    //TabLayout and ViewPager class
    private class CustomAdapter extends FragmentPagerAdapter {

        private String fragments[] = {"Edit Event", "Create Event"};

        public CustomAdapter(FragmentManager fragmentManager, Context context) {
            super(fragmentManager);
        }

        @Override
        public Fragment getItem(int position) {
            switch (position) {
                case 0:
                    return new EditEventFragment();
                case 1:
                    return new CreateEventFragment();
                default:
                    return null;
            }
        }

        @Override
        public int getCount() {
            return fragments.length;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return fragments[position];
        }

    }

}

还有我的孩子片段代码.我希望这些代码仅在用户滑动到子选项卡时执行.任何帮助都非常感谢，谢谢

And my child fragment code. I want these code only execute whenever the user slide to the child tab. Any help is much appreciate, Thanks

@Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        //Initializing our listEvents list
        listEvents = new ArrayList();

        recyclerView.setHasFixedSize(true);
        layoutManager = new LinearLayoutManager(getContext());
        recyclerView.setLayoutManager(layoutManager);

        adapter = new EventAdapterEdit(getContext(),listEvents);
        recyclerView.setAdapter(adapter);


        requestQueue = Volley.newRequestQueue(getContext());

        adapter = new EventAdapterEdit(getContext(),listEvents);
        recyclerView.setAdapter(adapter);

        getEventDetailRespond(requestQueue);

推荐答案

@Override public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
}

您可以在 ViewPager Adapter

if(isVisibleToUser){//dosomething when the fragment is visible}
else{//dosomething else.}

注意不要在那里初始化视图，而是在 onViewCreated 中初始化您的视图并调用您想要在 setUserVisibleHint 上执行的方法.另一种丑陋的方法是将滚动侦听器添加到您的 ViewPager 并获取当前项目位置并触发片段内的操作.要从 ViewPager Adapter 获取片段，您可以这样做:

be aware to do not initialize views there or anything rather, init your views within onViewCreated and call the method that you wanna execute on setUserVisibleHint. another ugly way is to add a scroll listener to your ViewPager and get the current item position and trigger an action that is within the fragment. to get the fragment from the ViewPager Adapter you can do such :

 MyFragment frag = (MyFragment) pager.getAdapter().instantiateItem(pager, position);

然后你可以调用 MyFragment 中的方法

then you could call a method that is within MyFragment

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