片段集工具栏标题，但显示下一个片段标题

Question

I am pretty new to Android development and I am trying to make a tabbed activity where the title changes according to the fragment. I tried using the following code which I found online, but when the first fragment is loaded, the second fragment title is shown at the toolbar instead.

public class TabbedActivity extends AppCompatActivity {

private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;
public Toolbar toolbar;

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

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

    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);

    tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));
    mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        switch(position){
            case 0:
                return new FragmentActivity_1();
            case 1:
                return new FragmentActivity_2();
            case 2:
                return new FragmentActivity_3();
            case 3:
                return new FragmentActivity_4();
            case 4:
                return new FragmentActivity_5();
        }
        return null;
    }

    @Override
    public int getCount() {
        return 5;
    }
}
}

One of the Fragment codes:

public class FragmentActivity_chat extends Fragment{

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState){
    View view = inflater.inflate(R.layout.chat_tabbed, container, false);

    ((TabbedActivity)getActivity()).toolbar.setTitle("Fragment 1");

    return view;
}
}

The Tabbed Activity XML:

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="com.android.MyApp.TabbedActivity">

<android.support.design.widget.AppBarLayout
    android:id="@+id/appbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/AppTheme.AppBarOverlay">

    <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/AppTheme.PopupOverlay"
        app:title="@string/app_name">

    </android.support.v7.widget.Toolbar>

    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimaryLight"
        app:tabMode="fixed"
        app:tabGravity="fill">

        <android.support.design.widget.TabItem
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:icon="@drawable/ic_person_black_24dp"/>

        <android.support.design.widget.TabItem
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:icon="@drawable/ic_chat_black_24dp"/>

        <android.support.design.widget.TabItem
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:icon="@drawable/ic_location_on_black_24dp"/>

        <android.support.design.widget.TabItem
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:icon="@drawable/ic_group_black_24dp"/>

        <android.support.design.widget.TabItem
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:icon="@drawable/ic_settings_black_24dp"/>

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

<android.support.v4.view.ViewPager
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />
</android.support.design.widget.CoordinatorLayout>

Any help is truly appreciated.

Answer 1

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public String[] tabtitles = {"fag1", "frag2", "frag3", "farg4", "farg5"};

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

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        Fragment fragment = null;
        switch (position) {
            case 0:
                fragment = new Fragment1();
                break;
            case 1:
                fragment = new Fragment2();
                break;
            case 2:
                fragment = new Fragment3();
                break;
            case 3:
                fragment = new Fragment4();
                break;
            case 4:
                fragment = new Fragment5();
                break;

            default:
                break;
        }
        // Return a PlaceholderFragment (defined as a static inner class below).
        return fragment;
    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 5;
    }


    @Override
    public CharSequence getPageTitle(int position) {
        return tabtitles[position];
    }
}

Answer 2

Figure out that the ViewPager is created, the first tab is created and the second tab is created also(for performance reason or something else, see setOffscreenPageLimit method( the default value is 1 )). So, the second tab is created after the first one. This is the reason why the text of the second tab is displayed.

You should check which tab is displaying before updating the title

Hopes it helps

Answer 3

You can try this .

1.use addOnTabSelectedListener

2.when onTabSelected is selected , you can setToolbarTitle(mTitleNames[pos]);

3.and remove ((TabbedActivity)getActivity()).toolbar.setTitle("Fragment 1"); in your fragment

final String[] mTitleNames = {"Fragment 1", "Fragment 2", "Fragment 3", "Fragment 4","Fragment 5"};

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

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

    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);

    mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    // set default title
    setActionBarTitle(mTitleNames[0]);
    // add here
    tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            int pos = tab.getPosition();
            setToolbarTitle(mTitleNames[pos]);
        }

        @Override
        public void onTabUnselected(TabLayout.Tab tab) {

        }

        @Override
        public void onTabReselected(TabLayout.Tab tab) {

        }
    });
}

/**
 * set toolbar title
 * @param title
 */
public void setToolbarTitle(String title) {
    getSupportActionBar().setTitle(title);
}

Answer 4

Use below code and your problem will be solved:

public class TabbedActivity extends AppCompatActivity {

    private SectionsPagerAdapter mSectionsPagerAdapter;
    private ViewPager mViewPager;
    public Toolbar toolbar;
    public String[] tabtitles = {"FragmentActivity_1", "FragmentActivity_2", "FragmentActivity_3", "FragmentActivity_4", "FragmentActivity_5"};
    public int[] icons = {R.mipmap.ic_launcher_round, R.mipmap.ic_launcher_round, R.mipmap.ic_launcher_round, R.mipmap.ic_launcher_round, R.mipmap.ic_launcher_round};

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

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


        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);

        tabLayout.setupWithViewPager(mViewPager);
        setTabIcon(tabLayout);

        mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                getSupportActionBar().setTitle(tabtitles[position]);

            }

            @Override
            public void onPageSelected(int position) {
                getSupportActionBar().setTitle(tabtitles[position]);

            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });

    }

    private void setTabIcon(TabLayout tabLayout) {
        int count = tabLayout.getTabCount();
        for (int i = 0; i < count; i++) {
            tabLayout.getTabAt(i).setIcon(icons[i]);
        }
    }


    public class SectionsPagerAdapter extends FragmentPagerAdapter {


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

        @Override
        public Fragment getItem(int position) {

            Fragment fragment = null;

            switch (position) {
                case 0:
                    fragment = new FragmentActivity_1();
                    break;
                case 1:
                    fragment = new FragmentActivity_2();
                    break;
                case 2:
                    fragment = new FragmentActivity_3();
                    break;
                case 3:
                    fragment = new FragmentActivity_4();
                    break;
                case 4:
                    fragment = new FragmentActivity_5();
                    break;
                default:
                    fragment = new FragmentActivity_1();
                    break;
            }
            return fragment;
        }

        @Override
        public int getCount() {
            return 5;
        }

    }
}

I have tested this code and it works fine, check image.