OnBackPressed in Tabbed-FragmentActivity not working

Question

I am showing multiple fragments in tabs with view pager and navigation drawer too. I defined a TabFragment which controls all the fragments.
I want to show a Exit Dialogue and finish the app.
But when I press Back Button it showed blank screen.
I even commented the onbackpressed method but still it showed the blank screen when I pressed the back button.
I have tried this: Android onBackPressed() not working but couldn't.

Main Activity

public class MainActivity extends AppCompatActivity {
    Toolbar toolbar;
    DrawerLayout mDrawerLayout;
    NavigationView mNavigationView;
    FragmentManager mFragmentManager;
    FragmentTransaction mFragmentTransaction;
    SharedPreferences preferences;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        preferences = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        if (toolbar != null) {
            setSupportActionBar(toolbar);
        }
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mNavigationView = (NavigationView) findViewById(R.id.main_drawer);
        View headerView = LayoutInflater.from(this).inflate(R.layout.drawer_header, null);
        mNavigationView.addHeaderView(headerView);
        mNavigationView.getHeaderView(0).setVisibility(View.GONE);

        int width = getResources().getDisplayMetrics().widthPixels / 2;
        DrawerLayout.LayoutParams params = (android.support.v4.widget.DrawerLayout.LayoutParams) mNavigationView.getLayoutParams();
        params.width = width;

        mNavigationView.setLayoutParams(params);
        mFragmentTransaction = mFragmentManager.beginTransaction();
        mFragmentTransaction.replace(R.id.frame_container, new TabFragment()).commit();

        mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(MenuItem menuItem) {
                menuItem.setChecked(true);
                mDrawerLayout.closeDrawers();
                if (menuItem.getItemId() == R.id.Top) {
                    FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
                    fragmentTransaction.replace(R.id.frame_container, new TabFragment()).commit();
                }
                if (menuItem.getItemId() == R.id.Latest) {
                    FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
                    fragmentTransaction.replace(R.id.frame_container, new Fragment1()).commit();
                }
                return false;
            }
        });

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, toolbar, R.string.drawer_open, R.string.drawer_close);
        mDrawerLayout.setDrawerListener(mDrawerToggle);
        mDrawerToggle.syncState();
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            ExitDialogue();
            super.onBackPressed();
        }
    }

    public void ExitDialogue() {
        AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
        builder.setTitle(R.string.app_name);
        builder.setIcon(R.mipmap.ic_launcher);
        builder.setMessage("Do you want to exit?")
                .setCancelable(false)
                .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        finish();
                    }
                })
                .setNegativeButton("No", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        dialog.cancel();
                    }
                });
        AlertDialog alert = builder.create();
        alert.show();
    }
}

The Tab Fragment actually loads the 2 fragments in tabs with view pager.

Tab Fragment

public class TabFragment extends Fragment {
    private TabLayout tabLayout;
    private ViewPager viewPager;
    private static int int_items = 2;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.tab_layout, container, false);
        tabLayout = (TabLayout) v.findViewById(R.id.tabs);
        viewPager = (ViewPager) v.findViewById(R.id.viewpager);
        viewPager.setAdapter(new MyAdapter(getChildFragmentManager()));
        viewPager.setOffscreenPageLimit(int_items - 1);
        viewPager.setPageTransformer(true, new DepthPageTransformer());
        tabLayout.post(new Runnable() {
            @Override
            public void run() {
                tabLayout.setupWithViewPager(viewPager);
            }
        });
        return v;
    }

    class MyAdapter extends FragmentPagerAdapter {
        MyAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            switch (position) {
                case 0:
                    return new Fragment1();
                case 1:
                    return new Fragment2();
            }
            return null;
        }

        @Override
        public int getCount() {
            return int_items;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return getResources().getString(R.string.tab1);
                case 1:
                    return getResources().getString(R.string.tab2);
            }
            return null;
        }
    }
}

Santosh Bangar · Accepted Answer · 2017-02-20T17:54:17.310

**CREATE YOUR MAINACTIVITY SUCH AS:**

public class MainActivity extends AppCompatActivity {

 public ViewPager viewPager;
 private ArrayList<Fragment> allPagerData;
   private MainactivityPagerAdapter mainAdapter;

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

        setContentView(R.layout.activity_main);


        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.addTab(tabLayout.newTab().setText("Fragment1"));
        tabLayout.addTab(tabLayout.newTab().setText("Fragment1"));

        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);

        viewPager = (ViewPager) findViewById(R.id.viewPager);
        final PagerAdapter adapter = new PagerAdapter
                (this.getSupportFragmentManager(), tabLayout.getTabCount());
        viewPager.setAdapter(adapter);

        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
                Log.e("onTabReselected: ",":"+tab);
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
                Log.e("onTabReselected: ",":"+tab);
            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
                Log.e("onTabReselected: ",":"+tab);
            }
        });

        initViews();
    }

    public void initViews(){

        createPager();

        mainAdapter = new MainactivityPagerAdapter(this.getSupportFragmentManager(), allPagerData);
        viewPage.setAdapter(mainAdapter);
        viewPager.setCurrentItem(0);


        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            }

            @Override
            public void onPageSelected(int position) {


                if (position == allPagerData.size() - 1) {
                }
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
    }

    @Override
    public void createPager() {
        allPagerData = new ArrayList<>();

        Fragment1 fragment1 = new Fragment1();
        allPagerData.add(fragment1);

         Fragment2 fragment2 = new Fragment2();
        allPagerData.add(fragment2);


    }

        @Override
    public void onBackPressed() {
        if (viewPager.getCurrentItem() != 0) {
            viewPager.setCurrentItem(viewPager.getCurrentItem() - 1);
        }else {
            super.onBackPressed();      
            // do whatever want to do if you want finished activity you can
        }
    }
}

==============================================================

Your MainactivityPagerAdapter 


public class MainactivityPagerAdapter extends FragmentPagerAdapter {

    private final ArrayList<Fragment> allFragments;

    public MainactivityPagerAdapter(FragmentManager fm, ArrayList<Fragment> allFragments) {
        super(fm);
        this.allFragments = allFragments;
    }

    /**
     * Return the Fragment associated with a specified position.
     *
     * @param position
     */
    @Override
    public Fragment getItem(int position) {
        return allFragments.get(position);
    }

    /**
     * Return the number of views available.
     */
    @Override
    public int getCount() {

        return (allFragments != null) ? allFragments.size() : 0;
    }
}

========================================================================= Your PagerAdapter

public class PagerAdapter extends FragmentStatePagerAdapter {
    int mNumOfTabs;

    public PagerAdapter(FragmentManager fm, int NumOfTabs) {
        super(fm);
        this.mNumOfTabs = NumOfTabs;
    }

    @Override
    public Fragment getItem(int position) {

        switch (position) {
            case 0:
                Fragment1 tab1 = new Fragment1();
                return tab1;
            case 1:
                Fragment2 tab2 = new Fragment2();
                return tab2;


            default:
                return null;
        }
    }

    @Override
    public int getItemPosition(Object object) {

        return super.getItemPosition(object);
    }

    @Override
    public int getCount() {
        return mNumOfTabs;
    }
}

score 0 · Answer 2 · answered Feb 20 '17 at 08:41

0

Remove super.onBackPressed(); from onBackPressed() and try.

answered Feb 20 '17 at 08:41

Pratik Popat

2,891
20
31

score 0 · Answer 3 · answered Feb 20 '17 at 08:55

0

Problem

when I press Back Button it showed blank screen.

Try this.

@Override
public void onBackPressed() {
    // removed unnecessary view binding code.
    if (mDrawerLayout.isDrawerOpen(GravityCompat.START)) {
        mDrawerLayout.closeDrawer(GravityCompat.START);
    } else {
        ExitDialogue();
        //removed super.onBackPressed
    }
}

answered Feb 20 '17 at 08:55

Ethan Choi

2,339
18
28

I have tried the above code but still showing blank screen. I even commented the onbackpressed method but its still showing blank screen. – Omer Danish Feb 20 '17 at 09:07

score 0 · Answer 4 · answered Feb 20 '17 at 09:16

0

Make your MainActivity is a parent Activity to handle your Tabfragment the issue is your parent fragment cannot handle your child tabfragment so onbackpress is not working here.

answered Feb 20 '17 at 09:16

Santosh Bangar

58
1
8

How can I do it? Give any example code or reference – Omer Danish Feb 20 '17 at 12:20
I am stuck on it ... help me – Omer Danish Feb 20 '17 at 15:38
@OmerDanish you tried my code for fragment and backpress issue ? – Santosh Bangar Feb 21 '17 at 08:57

score 0 · Answer 5 · answered Feb 20 '17 at 18:03

Since you have not posted the logs, these are the things you can check..

Try checking using a breakpoint in the onBackPress() method..to check if the control comes there or not.
As said earlier bind the mDrawerLayout on onCreate method and make it public variable.
Check if the Fragment and FragmentManager are references to v4.Fragment and v4.FragmentManager ( must be same )

OnBackPressed in Tabbed-FragmentActivity not working

5 Answers5