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FragmentStatePagerAdapter

abstract class FragmentStatePagerAdapter : PagerAdapter

kotlin.Any
   ↳ androidx.viewpager.widget.PagerAdapter
     ↳ androidx.fragment.app.FragmentStatePagerAdapter

Implementation of PagerAdapter that uses a Fragment to manage each page. This class also handles saving and restoring of fragment's state.

This version of the pager is more useful when there are a large number of pages, working more like a list view. When pages are not visible to the user, their entire fragment may be destroyed, only keeping the saved state of that fragment. This allows the pager to hold on to much less memory associated with each visited page as compared to FragmentPagerAdapter at the cost of potentially more overhead when switching between pages.

When using FragmentPagerAdapter the host ViewPager must have a valid ID set.

Subclasses only need to implement getItem and getCount to have a working adapter.

Here is an example implementation of a pager containing fragments of lists:
public class FragmentStatePagerSupport extends FragmentActivity {
    static final int NUM_ITEMS = 10;

    MyAdapter mAdapter;

    ViewPager mPager;

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

        mAdapter = new MyAdapter(getSupportFragmentManager());

        mPager = (ViewPager)findViewById(R.id.pager);
        mPager.setAdapter(mAdapter);

        // Watch for button clicks.
        Button button = (Button)findViewById(R.id.goto_first);
        button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                mPager.setCurrentItem(0);
            }
        });
        button = (Button)findViewById(R.id.goto_last);
        button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                mPager.setCurrentItem(NUM_ITEMS-1);
            }
        });
    }

    public static class MyAdapter extends FragmentStatePagerAdapter {
        public MyAdapter(FragmentManager fm) {
            super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
        }

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

        @Override
        public Fragment getItem(int position) {
            return ArrayListFragment.newInstance(position);
        }
    }

    public static class ArrayListFragment extends ListFragment {
        int mNum;

        /**
         * Create a new instance of CountingFragment, providing "num"
         * as an argument.
         */
        static ArrayListFragment newInstance(int num) {
            ArrayListFragment f = new ArrayListFragment();

            // Supply num input as an argument.
            Bundle args = new Bundle();
            args.putInt("num", num);
            f.setArguments(args);

            return f;
        }

        /**
         * When creating, retrieve this instance's number from its arguments.
         */
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            mNum = getArguments() != null ? getArguments().getInt("num") : 1;
        }

        /**
         * The Fragment's UI is just a simple text view showing its
         * instance number.
         */
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View v = inflater.inflate(R.layout.fragment_pager_list, container, false);
            View tv = v.findViewById(R.id.text);
            ((TextView)tv).setText("Fragment #" + mNum);
            return v;
        }

        @Override
        public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
            super.onViewCreated(view, savedInstanceState);
            setListAdapter(new ArrayAdapter<String>(getActivity(),
                    android.R.layout.simple_list_item_1, Cheeses.sCheeseStrings));
        }

        @Override
        public void onListItemClick(ListView l, View v, int position, long id) {
            Log.i("FragmentList", "Item clicked: " + id);
        }
    }
}
The R.layout.fragment_pagerresource of the top-level fragment is:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical" android:padding="4dip"
              android:gravity="center_horizontal"
              android:layout_width="match_parent" android:layout_height="match_parent">

    <androidx.viewpager.widget.ViewPager
            android:id="@+id/pager"
            android:layout_width="match_parent"
            android:layout_height="0px"
            android:layout_weight="1">
    </androidx.viewpager.widget.ViewPager>

    <LinearLayout android:orientation="horizontal"
                  android:gravity="center" android:measureWithLargestChild="true"
                  android:layout_width="match_parent" android:layout_height="wrap_content"
                  android:layout_weight="0">
        <Button android:id="@+id/goto_first"
                android:layout_width="wrap_content" android:layout_height="wrap_content"
                android:text="@string/first">
        </Button>
        <Button android:id="@+id/goto_last"
                android:layout_width="wrap_content" android:layout_height="wrap_content"
                android:text="@string/last">
        </Button>
    </LinearLayout>
</LinearLayout>
The R.layout.fragment_pager_listresource containing each individual fragment's layout is:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:background="@android:drawable/gallery_thumb">

    <TextView android:id="@+id/text"
              android:layout_width="match_parent" android:layout_height="wrap_content"
              android:gravity="center_vertical|center_horizontal"
              android:textAppearance="?android:attr/textAppearanceMedium"
              android:text="@string/hello_world"/>

    <!-- The frame layout is here since we will be showing either
    the empty view or the list view.  -->
    <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="0dip"
            android:layout_weight="1" >
        <!-- Here is the list. Since we are using a ListActivity, we
             have to call it "@android:id/list" so ListActivity will
             find it -->
        <ListView android:id="@android:id/list"
                  android:layout_width="match_parent"
                  android:layout_height="match_parent"
                  android:drawSelectorOnTop="false"/>

        <!-- Here is the view to show if the list is empty -->
        <TextView android:id="@android:id/empty"
                  android:layout_width="match_parent"
                  android:layout_height="match_parent"
                  android:textAppearance="?android:attr/textAppearanceMedium"
                  android:text="No items."/>

    </FrameLayout>

</LinearLayout>

Summary

Constants

const Int

Indicates that only the current fragment will be in the RESUMED state.

const Int

This property is deprecated.

This behavior relies on the deprecated setUserVisibleHint API.

Public constructors

This function is deprecated.

use FragmentStatePagerAdapter with BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT

Constructor for FragmentStatePagerAdapter.

Public functions

Unit
destroyItem(container: ViewGroup, position: Int, object: Any)
Unit
finishUpdate(container: ViewGroup)
abstract Fragment
getItem(position: Int)

Return the Fragment associated with a specified position.

Any
instantiateItem(container: ViewGroup, position: Int)
Boolean
isViewFromObject(view: View, object: Any)
Unit
restoreState(state: Parcelable?, loader: ClassLoader?)
Parcelable?
Unit
setPrimaryItem(container: ViewGroup, position: Int, object: Any)
Unit
startUpdate(container: ViewGroup)

Inherited Constants

From androidx.viewpager.widget.PagerAdapter
const Int
const Int

Inherited functions

From androidx.viewpager.widget.PagerAdapter

Constants

BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT

const val BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT = 1: Int

Indicates that only the current fragment will be in the RESUMED state. All other Fragments are capped at STARTED.

See also
FragmentStatePagerAdapter

BEHAVIOR_SET_USER_VISIBLE_HINT

const val BEHAVIOR_SET_USER_VISIBLE_HINT = 0: Int

Indicates that setUserVisibleHint will be called when the current fragment changes.

See also
FragmentStatePagerAdapter

Public constructors

FragmentStatePagerAdapter

FragmentStatePagerAdapter(fm: FragmentManager)

Constructor for FragmentStatePagerAdapter that sets the fragment manager for the adapter. This is the equivalent of calling FragmentStatePagerAdapter and passing in BEHAVIOR_SET_USER_VISIBLE_HINT.

Fragments will have setUserVisibleHint called whenever the current Fragment changes.

Parameters
fm: FragmentManager

fragment manager that will interact with this adapter

FragmentStatePagerAdapter

FragmentStatePagerAdapter(
    fm: FragmentManager,
    @FragmentStatePagerAdapter.Behavior behavior: Int
)

Constructor for FragmentStatePagerAdapter. If BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT is passed in, then only the current Fragment is in the RESUMED state, while all other fragments are capped at STARTED. If BEHAVIOR_SET_USER_VISIBLE_HINT is passed, all fragments are in the RESUMED state and there will be callbacks to setUserVisibleHint.

Parameters
fm: FragmentManager

fragment manager that will interact with this adapter

@FragmentStatePagerAdapter.Behavior behavior: Int

determines if only current fragments are in a resumed state

Public functions

destroyItem

fun destroyItem(container: ViewGroup, position: Int, object: Any): Unit

finishUpdate

fun finishUpdate(container: ViewGroup): Unit

getItem

abstract fun getItem(position: Int): Fragment

Return the Fragment associated with a specified position.

instantiateItem

fun instantiateItem(container: ViewGroup, position: Int): Any

isViewFromObject

fun isViewFromObject(view: View, object: Any): Boolean

restoreState

fun restoreState(state: Parcelable?, loader: ClassLoader?): Unit

saveState

fun saveState(): Parcelable?

setPrimaryItem

fun setPrimaryItem(container: ViewGroup, position: Int, object: Any): Unit

startUpdate

fun startUpdate(container: ViewGroup): Unit