Unable to edit ActionBar title from Fragment in ViewPager

Question

I have a single Activity which hosts multiple fragments through a ViewPager. In the Activity's onCreate method I'm using the following code to change the ActionBar title:

    Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    if(getSupportActionBar() != null) {
        getSupportActionBar().setTitle(getResources().getString(R.string.custom_title));
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }

It works fine, but then I am unable to change it as soon as a Fragment becomes visible. In order to detect it I've implemented:

@Override
public void setUserVisibleHint(boolean isVisibleToUser) {

    super.setUserVisibleHint(isVisibleToUser);

    if (isVisibleToUser && getContext() != null) {
            ((MainActivity) getContext()).editActionBarTitle("new title");
    }
}

And here's the definition for editActionBarTitle:

public void editActionBarTitle(String title) {
     if(getSupportActionBar() != null) {
         getSupportActionBar().setTitle(title);
         getSupportActionBar().setDisplayHomeAsUpEnabled(true);
     }
}

I can see that the method gets called as soon as a fragment becomes visible, but it has no effect on the ActionBar's title. What am I missing in order to edit the title correctly?

---

EDIT

I've also tried implementing addOnPageChangeListener in the viewPager, I can see that the method onPageSelected gets called but it has no effect on the title, here's an example on MainActivity:

public class MainActivity extends BaseActivity {   

    private NoScrollViewPager mViewPager;
    private SectionsPagerAdapter mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Toolbar initialization
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        if(getSupportActionBar() != null) {
            getSupportActionBar().setTitle("MainActivity");
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        }

        // ViewPager initialization
        mViewPager = findViewById(R.id.containter);
        setupViewPager();
    }

    private void setupViewPager() {

        mAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        mAdapter.addFragment(new Fragment1(), "Fragment 1");
        mAdapter.addFragment(new Fragment2(), "Fragment 2");
        mAdapter.addFragment(new Fragment3(), "Fragment 3");

        mViewPager.setOffscreenPageLimit(mAdapter.getCount());
        mViewPager.setAdapter(mAdapter);

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

            @Override
            public void onPageSelected(int position) {
                setTitle("fragment " + position);
                if(getSupportActionBar() != null) {
                    getSupportActionBar().setTitle("fragment " + position);
                }
            }

            @Override
            public void onPageScrollStateChanged(int state) { }
        });
    }

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

This is the custom ViewPager class:

public class NoScrollViewPager extends ViewPager {

    // Disable horizontal scrolling in ViewPager
    private boolean isPagingEnabled = false;

    public NoScrollViewPager(Context context) {
        super(context);
    }

    public NoScrollViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    @SuppressLint("AndroidLintClickableViewAccessibility")
    public boolean onTouchEvent(MotionEvent event) {
        return this.isPagingEnabled && super.onTouchEvent(event);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        return this.isPagingEnabled && super.onInterceptTouchEvent(event);
    }

    public void setPagingEnabled(boolean b) {
        this.isPagingEnabled = b;
    }
}

And this is the custom Adapter class:

public class SectionsPagerAdapter extends FragmentStatePagerAdapter {

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

    private FragmentManager fragmentManager;

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
        fragmentManager = fm;
    }

    public void addFragment(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
    }

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

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

    @Override
    public int getItemPosition(Object object) { return POSITION_NONE; }

}

Answer 1

Try this in your onCreateView method into fragment. May be it will helps you.

if(getActivity() != null){
     getActivity().setTitle("Your title");
}

If you used ViewPager inside a fragment then you can use

@Override
    public void setUserVisibleHint(boolean isVisible) {
        super.setUserVisibleHint(isVisible);

        if (isVisible) {
            if(getActivity() != null){
               getActivity().setTitle("Your title");
            }
        }
    }

Answer 2

You can also use viewPager.addOnPageChangeListener()

• Add a listener that will be invoked whenever the page changes or is incrementally scrolled

In viewPager.addOnPageChangeListener() you need to set title in your actionbar inside onPageSelected()

which returns the current the current selected page in viewpager

SAMPLE CODE

    viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int i, float v, int i1) {

        }

        @Override
        public void onPageSelected(int i) {

            if (i == 0) {
                getSupportActionBar().setTitle("Fragment One");
            } else if (i == 1) {
                getSupportActionBar().setTitle("Fragment Two");
            } else if (i == 2) {
                getSupportActionBar().setTitle("Fragment three");
            } else if (i == 3) {
                getSupportActionBar().setTitle("Fragment four");
            } else if (i == 4) {
                getSupportActionBar().setTitle("Fragment Five");
            }

        }

        @Override
        public void onPageScrollStateChanged(int i) {

        }
    });

here is the working code for me

activity code

import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;


public class HomeActivity extends AppCompatActivity {


    private NoScrollViewPager mViewPager;
    private SectionsPagerAdapter mAdapter;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        // Toolbar initialization
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        getSupportActionBar().setTitle("Fragment One");
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        // ViewPager initialization
        mViewPager = findViewById(R.id.containter);

        findViewById(R.id.btnOne).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mViewPager.setCurrentItem(0);
            }
        });
        findViewById(R.id.btnTwo).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mViewPager.setCurrentItem(1);
            }
        });
        findViewById(R.id.btnThree).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mViewPager.setCurrentItem(2);
            }
        });

        mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int i, float v, int i1) {

            }

            @Override
            public void onPageSelected(int i) {

                if (i == 0) {
                    getSupportActionBar().setTitle("Fragment One");
                } else if (i == 1) {
                    getSupportActionBar().setTitle("Fragment Two");
                } else if (i == 2) {
                    getSupportActionBar().setTitle("Fragment three");
                }

            }

            @Override
            public void onPageScrollStateChanged(int i) {

            }
        });


        setupViewPager();


    }

    private void setupViewPager() {

        mAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        mAdapter.addFragment(new Fragment1(), "Fragment 1");
        mAdapter.addFragment(new Fragment2(), "Fragment 2");
        mAdapter.addFragment(new Fragment3(), "Fragment 3");

        mViewPager.setOffscreenPageLimit(mAdapter.getCount());
        mViewPager.setAdapter(mAdapter);

        // viewPager event listener
    }


}

Layout

<android.support.design.widget.CoordinatorLayout 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.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|enterAlways"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

    </android.support.design.widget.AppBarLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btnOne"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Frag 1" />

        <Button
            android:id="@+id/btnTwo"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Frag 2" />


        <Button
            android:id="@+id/btnThree"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Frag 3" />

    </LinearLayout>

    <neel.com.demo.NoScrollViewPager
        android:id="@+id/containter"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />
</android.support.design.widget.CoordinatorLayout>

OUTPUT

https://www.youtube.com/watch?v=ytJogOkj1zQ