MasterDetailFragmentHelper.java

package org.michenux.drodrolib.ui.fragment;

import android.content.res.Configuration;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;

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

public class MasterDetailFragmentHelper {
    public static MasterDetailFragments getCurrentFragments(int masterView, int detailView, Class<? extends Fragment> detailClass,
                                                            FragmentManager fm) {
        MasterDetailFragments masterDetailFragments = new MasterDetailFragments();

        List<Fragment> fragmentToRemove = new ArrayList<>();

        Fragment frag1 = fm.findFragmentById(masterView);
        if (frag1 != null) {
            if (detailClass.isAssignableFrom(frag1.getClass())) {
                masterDetailFragments.detail = frag1;

                fm.popBackStackImmediate();
                fragmentToRemove.add(frag1);

                frag1 = fm.findFragmentById(masterView);
                masterDetailFragments.master = frag1;
                fragmentToRemove.add(frag1);
            } else {
                masterDetailFragments.master = frag1;
                fragmentToRemove.add(frag1);
            }
        }

        Fragment frag2 = fm.findFragmentById(detailView);
        if (frag2 != null) {
            fragmentToRemove.add(frag2);
            if (masterDetailFragments.detail == null) {
                masterDetailFragments.detail = frag2;
            }
        }

        FragmentTransaction ft = fm.beginTransaction();
        for (Fragment f : fragmentToRemove) {
            ft.remove(f);
        }
        ft.commit();
        fm.executePendingTransactions();

        return masterDetailFragments;
    }

    public static void initFragments(MasterDetailFragments fragments, int masterView, int detailView, Configuration configuration, FragmentManager fm) {
        boolean dualPanel = configuration.orientation == Configuration.ORIENTATION_LANDSCAPE;

        if (dualPanel) {
            FragmentTransaction ft = fm.beginTransaction();
            ft.add(masterView, fragments.master);
            if (fragments.detail != null) {
                ft.add(detailView, fragments.detail);
            }
            ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
            ft.commit();
        } else {
            FragmentTransaction ft = fm.beginTransaction();
            ft.add(masterView, fragments.master);
            ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
            ft.commit();

            if (fragments.detail != null) {
                ft = fm.beginTransaction();
                ft.add(masterView, fragments.detail);
                ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
                ft.addToBackStack(null);
                ft.commit();
            }
        }
    }
}