{% setvar book_path %}/reference/androidx/_book.yaml{% endsetvar %} {% include "_shared/_reference-head-tags.html" %}

FragmentPagerAdapter

{% setvar page_path %}androidx/fragment/app/FragmentPagerAdapter.html{% endsetvar %} {% setvar can_switch %}1{% endsetvar %} {% include "reference/_java_switcher2.md" %}

public abstract class FragmentPagerAdapter


Implementation of PagerAdapter that represents each page as a Fragment that is persistently kept in the fragment manager as long as the user can return to the page.

This version of the pager is best for use when there are a handful of typically more static fragments to be paged through, such as a set of tabs. The fragment of each page the user visits will be kept in memory, though its view hierarchy may be destroyed when not visible. This can result in using a significant amount of memory since fragment instances can hold on to an arbitrary amount of state. For larger sets of pages, consider FragmentStatePagerAdapter.

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 FragmentPagerSupport 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 FragmentPagerAdapter {
        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

static final @NonNull int

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

static final @NonNull int

This field is deprecated.

This behavior relies on the deprecated Fragment#setUserVisibleHint(boolean) API.

Public constructors

This method is deprecated.

use FragmentPagerAdapter with BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT

Constructor for FragmentPagerAdapter.

Public methods

@NonNull void
destroyItem(
    @NonNull ViewGroup container,
    @NonNull int position,
    @NonNull Object object
)
@NonNull void
finishUpdate(@NonNull ViewGroup container)
abstract @NonNull Fragment
getItem(@NonNull int position)

Return the Fragment associated with a specified position.

@NonNull long
getItemId(@NonNull int position)

Return a unique identifier for the item at the given position.

@NonNull Object
instantiateItem(@NonNull ViewGroup container, @NonNull int position)
@NonNull boolean
isViewFromObject(@NonNull View view, @NonNull Object object)
@NonNull void
restoreState(@Nullable Parcelable state, @Nullable ClassLoader loader)
@Nullable Parcelable
@NonNull void
setPrimaryItem(
    @NonNull ViewGroup container,
    @NonNull int position,
    @NonNull Object object
)
@NonNull void
startUpdate(@NonNull ViewGroup container)

Constants

BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT

@NonNull
public static final @NonNull int BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT

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

See also
FragmentPagerAdapter

#FragmentPagerAdapter(FragmentManager, int)

BEHAVIOR_SET_USER_VISIBLE_HINT

@NonNull
public static final @NonNull int BEHAVIOR_SET_USER_VISIBLE_HINT

Indicates that Fragment#setUserVisibleHint(boolean) will be called when the current fragment changes.

See also
FragmentPagerAdapter

#FragmentPagerAdapter(FragmentManager, int)

Public constructors

FragmentPagerAdapter

@NonNull
public FragmentPagerAdapter(@NonNull FragmentManager fm)

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

Fragments will have Fragment#setUserVisibleHint(boolean) called whenever the current Fragment changes.

Parameters
@NonNull FragmentManager fm

fragment manager that will interact with this adapter

FragmentPagerAdapter

@NonNull
public FragmentPagerAdapter(@NonNull FragmentManager fm, @NonNull int behavior)

Constructor for FragmentPagerAdapter. If BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT is passed in, then only the current Fragment is in the Lifecycle.State#RESUMED state. All other fragments are capped at Lifecycle.State#STARTED. If BEHAVIOR_SET_USER_VISIBLE_HINT is passed, all fragments are in the Lifecycle.State#RESUMED state and there will be callbacks to Fragment#setUserVisibleHint(boolean).

Parameters
@NonNull FragmentManager fm

fragment manager that will interact with this adapter

@NonNull int behavior

determines if only current fragments are in a resumed stateValue is BEHAVIOR_SET_USER_VISIBLE_HINT, or BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT

Public methods

destroyItem

@NonNull
public void destroyItem(
    @NonNull ViewGroup container,
    @NonNull int position,
    @NonNull Object object
)

finishUpdate

@NonNull
public void finishUpdate(@NonNull ViewGroup container)

getItem

@NonNull
public abstract Fragment getItem(@NonNull int position)

Return the Fragment associated with a specified position.

getItemId

@NonNull
public long getItemId(@NonNull int position)

Return a unique identifier for the item at the given position.

The default implementation returns the given position. Subclasses should override this method if the positions of items can change.

Parameters
@NonNull int position

Position within this adapter

Returns
long

Unique identifier for the item at position

instantiateItem

@NonNull
public Object instantiateItem(@NonNull ViewGroup container, @NonNull int position)

isViewFromObject

@NonNull
public boolean isViewFromObject(@NonNull View view, @NonNull Object object)

restoreState

@NonNull
public void restoreState(@Nullable Parcelable state, @Nullable ClassLoader loader)

saveState

@Nullable
@NonNull
public Parcelable saveState()

setPrimaryItem

@NonNull
public void setPrimaryItem(
    @NonNull ViewGroup container,
    @NonNull int position,
    @NonNull Object object
)

startUpdate

@NonNull
public void startUpdate(@NonNull ViewGroup container)