滑动标签时调用API

Question

I have a tab layout with 3 tabs.Each one of the tabs need to display some data from API calling (I'm using Retrofit).

So , I have the main activity when user opens that activity I fetch the data for the first tab then display the view

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        context = this;

        if (Application.isConnected()) {
            getTrips();

        } else {
            Toast.makeText(this , "No internet Connection" , Toast.LENGTH_LONG).show();
            setContentView(R.layout.no_internet_connection);
        }
   }

So in the success of the API call I inflate the view as below

   public void inflatingView () {

        setContentView(R.layout.activity_mytrip);
        context = this;

        tvTitle = findViewById(R.id.tv_title);
        tabLayout = findViewById(R.id.tablayout);
        tvTitle.setText("Trips");
        tabLayout.addTab(tabLayout.newTab().setText("My Trips"));
        tabLayout.addTab(tabLayout.newTab().setText("Unclosed Trips"));
        tabLayout.addTab(tabLayout.newTab().setText("UnApproved Trips"));


        viewPager = findViewById(R.id.viewpager);
        myTripAdapter = new MyTripAdapter(getSupportFragmentManager(),tabLayout.getTabCount());
        viewPager.setAdapter(myTripAdapter);
        viewPager.setOffscreenPageLimit(3);


        tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {

                switch (tabLayout.getSelectedTabPosition()) { 

                    case 0 :
                        Log.d("test" , "first tab");
                        break;
                    case 1 :
                        Log.d("test" , "Second tab");
                        getTab2Data();
                        break;
                    case 2 :
                        Log.d("test" , "Third tab");
                        break;
                }

                viewPager.setCurrentItem(tabLayout.getSelectedTabPosition());
            }

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

            }

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

            }
        });

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

    }

So , The data for first fragment in first tab is obtained , My problem is with fragment 2 and 3.I only want to call the API when user swiping. As you see above I tried to detect when user swipe to second tab then I call method to fetch data but unfortunately it's now working.

Do you have any idea on how to do this?

Answer 1

You should call API's inside the fragment probably in setUserVisibleHint method in android

boolean _areLecturesLoaded = false;

@Override
 public void setUserVisibleHint(boolean isVisibleToUser) {
     super.setUserVisibleHint(isVisibleToUser);
     if (isVisibleToUser && !_areLecturesLoaded ) {
      loadYourRetrofitData(); //Load your data here  
      _areLecturesLoaded = true;
     }
 }

Answer 2

Use this method in your fragment to get visibility state of fragment and then call your api thre.

@Override 
boolean getUserVisibleHint() {
    super.getUserVisibleHint()
    boolean isVisibleToUser=super.getUserVisibleHint()
    if(isVisibleToUser){
        //call api here
    }
    return isVisibleToUser
}