{% setvar book_path %}/reference/kotlin/androidx/_book.yaml{% endsetvar %} {% include "_shared/_reference-head-tags.html" %}
abstract class 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.
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_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"> <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_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 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>
Constants |
|
---|---|
Int |
Indicates that only the current fragment will be in the Lifecycle.State#RESUMED state. |
Int |
This property is deprecated. This behavior relies on the deprecated |
Public constructors |
|
---|---|
This function is deprecated. use |
|
FragmentStatePagerAdapter(fm: FragmentManager, behavior: Int) Constructor for |
Public functions |
|
---|---|
Unit |
destroyItem(container: ViewGroup, position: Int, object: Any) |
Unit |
finishUpdate(container: ViewGroup) |
abstract Fragment |
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) |
val BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT: Int
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 | |
---|---|
FragmentStatePagerAdapter |
#FragmentStatePagerAdapter(FragmentManager, int) |
val BEHAVIOR_SET_USER_VISIBLE_HINT: Int
Indicates that Fragment#setUserVisibleHint(boolean)
will be called when the current fragment changes.
See also | |
---|---|
FragmentStatePagerAdapter |
#FragmentStatePagerAdapter(FragmentManager, int) |
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 Fragment#setUserVisibleHint(boolean)
called whenever the current Fragment changes.
Parameters | |
---|---|
fm: FragmentManager |
fragment manager that will interact with this adapter |
FragmentStatePagerAdapter(fm: FragmentManager, behavior: Int)
Constructor for FragmentStatePagerAdapter
. If BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT
is passed in, then only the current Fragment is in the Lifecycle.State#RESUMED state, while 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 | |
---|---|
fm: FragmentManager |
fragment manager that will interact with this adapter |
behavior: Int |
determines if only current fragments are in a resumed stateValue is |