Home » Android » android – ViewPage Fragment disappear when reload again

android – ViewPage Fragment disappear when reload again

Posted by: admin June 15, 2020 Leave a comment

Questions:

The following is layout

test.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:orientation="vertical"
          android:layout_width="match_parent"
          android:layout_height="match_parent">

<Button android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:text="Click"
        android:id="@+id/button"
        />

<!-- Framelayout to display Fragments -->
<FrameLayout
        android:id="@+id/frame_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

test_detail.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:orientation="vertical"
          android:layout_width="match_parent"
          android:layout_height="match_parent">

<TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Hello"
        android:id="@+id/textView" android:layout_gravity="center_horizontal"/>
</LinearLayout>

common_view_pager_layout

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:orientation="vertical"
          android:layout_width="match_parent"
          android:layout_height="match_parent">

    <android.support.v4.view.ViewPager
        android:id="@+id/MainViewerPage"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        >
    <android.support.v4.view.PagerTabStrip
            android:id="@+id/TitlePageTabStrip"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </android.support.v4.view.ViewPager>

</LinearLayout>

The following is my Activity code

    public class TestFragmentActivity extends FragmentActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.test);

    Button button = (Button) this.findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            FragmentManager fragmentManager = getSupportFragmentManager();
            fragmentManager.beginTransaction()
                    .replace(R.id.frame_container, new HomeFragment()).commit();

        }
    });

    }

    public class HomeFragment extends Fragment {
    private PagerAdapter _adapter;

    public HomeFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.common_view_pager_layout, container, false);

        this._adapter = new PagerAdapter(TestFragmentActivity.this);
        this._adapter.add(new DetailFragment());

        ViewPager pager = (ViewPager) view.findViewById(R.id.MainViewerPage);
        pager.setAdapter(this._adapter);

        return view;
    }
    }


    public class DetailFragment extends Fragment {

    public DetailFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.test_detail, container, false);

        return rootView;
    }
    }


    public class PagerAdapter extends FragmentPagerAdapter {
    private ArrayList<Fragment> _fragments;

    public PagerAdapter(FragmentActivity activity) {
        super(activity.getSupportFragmentManager());

        this._fragments = new ArrayList<Fragment>();
    }

    public void add(Fragment fragment) {
        this._fragments.add(fragment);
    }

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

    @Override
    public CharSequence getPageTitle(int position) {
        return "Test";
    }

    @Override
    public int getCount() {
        return 1;
    }


    }
}

When I click a button the fragment in ViewPager was display
When I click a button the fragment in ViewPager was display

But when I click the button again the fragment disappear
enter image description here

Please help me.

How to&Answers:

try using this:

in the constructor of your adapter change this :

public class MyPagerAdapter extends FragmentPagerAdapter {
private ArrayList<Fragment> _fragments;

public MyPagerAdapter(FragmentManager activity) {
    super(activity);

    this._fragments = new ArrayList<Fragment>();
}

public void add(Fragment fragment) {
    this._fragments.add(fragment);
}

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

@Override
public CharSequence getPageTitle(int position) {
    return "Test";
}

@Override
public int getCount() {
    return 1;
}


}

and when you want to create the adapter send getChildFragmentManager() to its constructor

public class HomeFragment extends Fragment {
private MyPagerAdapter _adapter;

public HomeFragment() {
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.common_view_pager_layout, container, false);
    ViewPager pager = (ViewPager) view.findViewById(R.id.MainViewerPage);

    this._adapter = new MyPagerAdapter(getChildFragmentManager());
    this._adapter.add(new DetailFragment());


    pager.setAdapter(this._adapter);


    return view;
}
}

I test it and it works, any problem comment it.

Good Luck!

Answer:

In your Fragment class, in the onCreate() method, you have to call setRetainInstance(true) like this:

@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);     
    setRetainInstance(true);
}

This tells the FragmentManager to keep your fragments on reloads.
In addition, check your manifest file doesn’t have any

android:screenOrientation

config changes where you are basically saying you will handle reloads due to config changes yourself.

Answer:

In PagerFragment ‘s onResume() add this:

@Override
public void onResume() {
    super.onResume();

    for (Fragment fragment : getFragmentManager().getFragments()) {
        if (fragment instanceof Tab1Fragment || fragment instanceof Tab2Fragment) {
            FragmentTransaction ft = getFragmentManager().beginTransaction();
            ft.detach(fragment);
            ft.attach(fragment);
            ft.commit();
        }
    }
}

Answer:

Try to add this lines in your code:

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

and Add the below lines

pager.setOnPageChangeListener(new OnPageChangeListener() {
     @Override
     public void onPageSelected(int position) {
          ... anything you may need to do to handle pager state ...
          adapter.notifyDataSetChanged(); //this line will force all pages to be loaded fresh when changing between fragments
     }

Under

pager.setAdapter(adapter);

Hope this may help you!

Answer:

Ensure you pass the adapter instance the child fragment manager, not the fragment manager.

Like this:

this._adapter = new PagerAdapter(getChildFragmentManager());