当我点击 TabLayout 的选项卡或通过 viewpager 移动时，我想加载片段

Question

我有多个片段，都显示一些新闻

问题是，当我运行我的应用程序加载所有片段并从服务器获取所有片段数据时，但我想在移动到该特定片段时获取数据，所以请帮助我

我的代码在下面

MainActivity.Java

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    setToolbar();
    initView();
}

private void initView() {
    TabLayout tabLayout=(TabLayout)findViewById(R.id.tablayout);
    ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);

    addTabs(tabLayout,viewPager);

    BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
    navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
}

private void addTabs(TabLayout tabLayout, final ViewPager viewPager) {
    final PageAdapter pageAdapter = new PageAdapter(getSupportFragmentManager(), 5);
    tabLayout.addTab(tabLayout.newTab().setText(NewsConstant.HeadLines));
    tabLayout.addTab(tabLayout.newTab().setText(NewsConstant.Sports));
    tabLayout.addTab(tabLayout.newTab().setText(NewsConstant.Health));
    tabLayout.addTab(tabLayout.newTab().setText(NewsConstant.India));
    tabLayout.addTab(tabLayout.newTab().setText(NewsConstant.World));
    tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            viewPager.setCurrentItem(tab.getPosition());

        }

        @Override
        public void onTabUnselected(TabLayout.Tab tab) {

        }

        @Override
        public void onTabReselected(TabLayout.Tab tab) {

        }
    });
    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));

    viewPager.setAdapter(pageAdapter);
    viewPager.setOffscreenPageLimit(5);

}

PageAdapter.java

public class PageAdapter extends FragmentStatePagerAdapter {

int mNumOfTabs;

public PageAdapter(FragmentManager fm, int NumOfTabs) {
    super(fm);
    this.mNumOfTabs = NumOfTabs;
}

@Override
public Fragment getItem(int position) {
     return NewsFragment.newInstance(position,position+"");
}

@Override
public int getCount() {
    return mNumOfTabs;
}

NewFragment.java

public class NewsFragment extends Fragment {

private RecyclerView recyclerView;

public static NewsFragment newInstance(int index,String title) {
    NewsFragment fragment = new NewsFragment();
    Bundle args = new Bundle();
    args.putInt(NewsConstant.INDEX,index);
    args.putString(NewsConstant.TITLE,title);
    fragment.setArguments(args);

    return fragment;
}



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

    initView(view);
    getDataFromServer(); // Here i get data and display

    return view;
}

例如。

我在Activity中使用TabLayout、ViewPager来加载Fragments

我有 3 个 TAB 喜欢 标题 |运动 |好莱坞

我对所有 TAB 使用相同的片段所以当我点击 Hollywood TAB 然后从服务器获取数据并显示在那个 recyclerView

Answer 1

我曾经遇到过同样的问题 尝试使用

private boolean isViewShown = false;
@Override 
public void setUserVisibleHint(boolean isVisibleToUser) { 
     super.setUserVisibleHint(isVisibleToUser);      
if (getView() != null && isVisibleToUser) { 
     isViewShown = true; // fetchdata() contains logic to show data when page is selected mostly asynctask to fill the data 
     fetchData(); 
} else { 
     isViewShown = false; 
} }

调用你的 Api 或者当你到达这里的片段时你想看到什么

Answer 2

View pager 实际上会同时加载上一页、当前页和下一页。这是为了在滑动时获得无缝体验。这可以使用@Jius Lukose

提到的方法来控制

或者请参考答案 How can make my ViewPager load only one page at a time ie setOffscreenPageLimit(0);

当我点击 TabLayout 的选项卡或通过 viewpager 移动时，我想加载片段

I want to load fragment when i click on tab of TabLayout or move by viewpager

android

adapter

android-fragments

android-activity