如何使用 tabLayout 在 ViewPager 中显示片段？

Question

I'm trying to show fragments in viewPager with tabsLayout but the viewPager shows nothing. However, the tabs have been added to the view. I have also put some logs in the fragments just to make sure that they're created and it's showing the logs - nothing wrong with the fragments.

the layout that contains the tabs and viewPager:

 <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
    
        <com.google.android.material.tabs.TabLayout
            android:id="@+id/tabLayout"
            android:paddingLeft="8dp"
            android:paddingRight="8dp"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            app:tabIndicatorColor="@color/colorAccent"
            app:tabMode="fixed"
            app:tabSelectedTextColor="@color/colorAccent"
            app:tabTextAppearance="@style/customTabsStyle"
            app:tabTextColor="#000" />
    
        <androidx.viewpager.widget.ViewPager
            android:id="@+id/viewPager"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    
    </LinearLayout>

Then in MainActivity I have this code:

    tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.promotions)));
    tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.all_stores)));
    tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
    final HomeTabsAdapter tabsAdapter = new 
    HomeTabsAdapter(MainActivity.this,getSupportFragmentManager(),
            tabLayout.getTabCount());
    viewPager.setAdapter(tabsAdapter);
    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    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) {
    }
});

And this is part of HomeTabsAdapter:

public HomeTabsAdapter(Context c, FragmentManager fm, int totalTabs) {
super(fm);
context = c;
this.totalTabs = totalTabs;

}

@NonNull
@Override
public Fragment getItem(int position) {
    switch (position) {
        case 1:
            return getAllStoresFragment();
        default:
            return getPromotionsFragment();
    }

Note: Both fragments are of the same type but i'm showing different stuff based on the Arguments. (I'm using the getInstance(..) way to handle this using Bundle and Arguments).

What changes to this code could solve the issue?

Answer 1

The position starts at 0.

@NonNull
@Override
public Fragment getItem(int position) {
    switch (position) {
        case 0:
            return getAllStoresFragment();
        default:
            return getPromotionsFragment();
    }