public abstract class

FragmentStatePagerAdapter

extends PagerAdapter

Class Overview

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(int) and getCount() to have a working adapter.

Here is an example implementation of a pager containing fragments of lists:

public class FragmentStatePagerSupport extends Activity {    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(getFragmentManager());

        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() {            public void onClick(View v) {                mPager.setCurrentItem(0);            }        });        button = (Button)findViewById(R.id.goto_last);        button.setOnClickListener(new OnClickListener() {            public void onClick(View v) {                mPager.setCurrentItem(NUM_ITEMS-1);            }        });    }

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

        @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 onActivityCreated(Bundle savedInstanceState) {            super.onActivityCreated(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_pager resource 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">

    <android.support.v4.view.ViewPager            android:id="@+id/pager"            android:layout_width="match_parent"            android:layout_height="0px"            android:layout_weight="1">    </android.support.v4.view.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_list resource 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 emtpy -->        <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

[Expand] Inherited Constants
From class android.support.v4.view.PagerAdapter

[Expand] Inherited Methods
From class android.support.v4.view.PagerAdapter
From class java.lang.Object

Public Constructors

public FragmentStatePagerAdapter (FragmentManager fm)

Public Methods

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

Remove a page for the given position. The adapter is responsible for removing the view from its container, although it only must ensure this is done by the time it returns from finishUpdate(ViewGroup).

Parameters

public void finishUpdate (ViewGroup container)

Called when the a change in the shown pages has been completed. At this point you must ensure that all of the pages have actually been added or removed from the container as appropriate.

Parameters

public abstract Fragment getItem (int position)

Return the Fragment associated with a specified position.

public Object instantiateItem (ViewGroup container, int position)

Create the page for the given position. The adapter is responsible for adding the view to the container given here, although it only must ensure this is done by the time it returns from finishUpdate(ViewGroup).

Parameters

Returns

• Returns an Object representing the new page. This does not need to be a View, but can be some other container of the page.

public boolean isViewFromObject (View view, Object object)

Determines whether a page View is associated with a specific key object as returned by instantiateItem(ViewGroup, int). This method is required for a PagerAdapter to function properly.

Parameters

Returns

• true if view is associated with the key object object

public void restoreState (Parcelable state, ClassLoader loader)

Restore any instance state associated with this adapter and its pages that was previously saved by saveState().

Parameters

public Parcelable saveState ()

Save any instance state associated with this adapter and its pages that should be restored if the current UI state needs to be reconstructed.

Returns

• Saved state for this adapter

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

Called to inform the adapter of which item is currently considered to be the "primary", that is the one show to the user as the current page.

Parameters

public void startUpdate (ViewGroup container)

Called when a change in the shown pages is going to start being made.

Parameters

Except as noted, this content is licensed under Apache 2.0. For details and restrictions, see the Content License.

Android 4.4 r1 — 28 Aug 2014 0:14

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