Why FragmentStateAdapter not work in ViewPager2? [duplicate]

问题

Android Studio 3.6

I want in my activity to use 2 fragments inside ViewPager2.

Here my activity:

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;
public class QRBluetoothSwipeActivity extends AppCompatActivity {
    private ViewPager2 myViewPager2;
    private ViewPagerFragmentAdapter myAdapter;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        // Make sure this is before calling super.onCreate
        setTheme(R.style.AppTheme); // show splash screen
        super.onCreate(savedInstanceState);
        setContentView(R.layout.qr_bluetooth_swipe_activity);
        init();
    }

    private void init() {
        myAdapter = new ViewPagerFragmentAdapter(getSupportFragmentManager());
        myAdapter.addFragment(new BluetoothPageFragment());
        myAdapter.addFragment(new QrPageFragment());
        myViewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);
        myViewPager2.setAdapter(myAdapter);
    }

}

here ViewPagerFragmentAdapter

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.viewpager2.adapter.FragmentStateAdapter;

import java.util.ArrayList;

public class ViewPagerFragmentAdapter  extends FragmentStateAdapter {

    private ArrayList<Fragment> arrayList = new ArrayList<>();

    public ViewPagerFragmentAdapter(@NonNull FragmentManager fragmentManager) {
        super(fragmentManager);
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        return arrayList.get(position);
    }

    public void addFragment(Fragment fragment) {
        arrayList.add(fragment);
    }

    @Override
    public int getItemCount() {
        return arrayList.size();
    }
}

but I get compile error:

ViewPagerFragmentAdapter is not abstract and does not override abstract method createFragment(int) in FragmentStateAdapter

How I can fix this and use FRAGMENTS in ViewPager2 ?

Thanks

回答1:

FragmentStateAdapter in ViewPager2 is a little bit different than in ViewPager as follows:

Instead of implementing getCount(), implement getItemCount()
Instead of implementing getItem(int position), implement createFragment(int position)
Constructor signature is different by adding Lifecycle argument which should be included in super as well

So replace your ViewPagerFragmentAdapter with below

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.lifecycle.Lifecycle;
import androidx.viewpager2.adapter.FragmentStateAdapter;

import java.util.ArrayList;


public class ViewPagerFragmentAdapter extends FragmentStateAdapter {

    private ArrayList<Fragment> arrayList = new ArrayList<>();

    public ViewPagerFragmentAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle) {
        super(fragmentManager, lifecycle);
    }


    public void addFragment(Fragment fragment) {
        arrayList.add(fragment);
    }

    @Override
    public int getItemCount() {
        return arrayList.size();
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        // return your fragment that corresponds to this 'position'
        return arrayList.get(position);
    }

}

Also make sure to import/extebd the right adapter of ViewPager2

import androidx.viewpager2.adapter.FragmentStateAdapter;

Hope this helpful, and will be glad for more illustration

来源：https://stackoverflow.com/questions/58527131/why-fragmentstateadapter-not-work-in-viewpager2

标签

android

android-viewpager2