Why doesn't popBackStack revert to previous fragment with FragmentStatePagerAdapter?

Question

I have an order pager adapter

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;


import java.util.ArrayList;
import java.util.List;

public class OrderPagerAdapter extends FragmentStatePagerAdapter {

    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();
    private FragmentManager fm;

    public OrderPagerAdapter(FragmentManager fm) {
        super(fm);
        this.fm = fm;
    }

    public void addFragment(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
       fm.beginTransaction().addToBackStack(null).commit();
    }

    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList.size();
    }

}

Methods in my main order activity class

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_order);
    datasource = new Datasource(this);
    categoryFragment = new CategoryFragment();
    productFragment = new ProductFragment();
    detailFragment = new DetailFragment();
    mViewPager = (ViewPager) findViewById(R.id.pager2);
    mOrderPagerAdapter = new OrderPagerAdapter(getSupportFragmentManager());
    setupViewPager(mViewPager);
}

private void setupViewPager(ViewPager viewPager) {
    mOrderPagerAdapter.addFragment(categoryFragment, "category");
    mOrderPagerAdapter.addFragment(productFragment, "product");
    mOrderPagerAdapter.addFragment(detailFragment, "s");
    viewPager.setAdapter(mOrderPagerAdapter);
    }

public void setViewPager(int fragmentNumber) {
    mViewPager.setCurrentItem(fragmentNumber);
}

Popbackstack method

  @Override
    public void onBackPressed() {
       getSupportFragmentManager().popBackStack();
    }

Whenever I click the onBackPressed button the previous fragment isnt loading, why does this happen? I have tried multiple things such as adding to backstack and then committing. But none of the ways seem to be working.

You are using it inside viewpager? this method will work for you if you have added fragment with fragmentTransaction in any Layout. — Rahul Khurana, Oct 03 '18 at 10:05
yes im using viewpager. but the method isnt popping the previous fragment — John Travolta, Oct 03 '18 at 10:06
You need to use **FragmentTransaction** to any container not on ViewPager. — Rahul Khurana, Oct 03 '18 at 10:08
if you want to get back to previous page then use viewPager.setCurrentItem(viewPager.getCurrentItem() - 1); — Rahul Khurana, Oct 03 '18 at 10:09

score 0 · Accepted Answer · answered Oct 03 '18 at 12:06

0

You are using it inside viewpager? this method will work for you if you have added fragment with fragmentTransaction in any Layout/Container.

if you want to get back to previous page then use viewPager.setCurrentItem(viewPager.getCurrentItem() - 1);

answered Oct 03 '18 at 12:06

Rahul Khurana

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Why doesn't popBackStack revert to previous fragment with FragmentStatePagerAdapter?

1 Answers1