{% setvar book_path %}/reference/androidx/_book.yaml{% endsetvar %} {% include "_shared/_reference-head-tags.html" %}
public 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 |
|
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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 |
Public constructors |
|
---|---|
This method is deprecated. use |
|
FragmentStatePagerAdapter( Constructor for |
Public methods |
|
---|---|
@NonNull void |
destroyItem( |
@NonNull void |
finishUpdate(@NonNull ViewGroup container) |
abstract @NonNull Fragment |
Return the Fragment associated with a specified 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 void |
startUpdate(@NonNull ViewGroup container) |
@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 | |
---|---|
FragmentStatePagerAdapter |
#FragmentStatePagerAdapter(FragmentManager, int) |
@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 | |
---|---|
FragmentStatePagerAdapter |
#FragmentStatePagerAdapter(FragmentManager, int) |
@NonNull
publicFragmentStatePagerAdapter(@NonNull FragmentManager fm)
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 | |
---|---|
@NonNull FragmentManager fm |
fragment manager that will interact with this adapter |
@NonNull
public FragmentStatePagerAdapter(
@NonNull FragmentManager fm,
@NonNull int behavior
)
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 | |
---|---|
@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 |
@NonNull
public void destroyItem(
@NonNull ViewGroup container,
@NonNull int position,
@NonNull Object object
)
@NonNull
public abstract Fragment getItem(@NonNull int position)
Return the Fragment associated with a specified position.
@NonNull
public Object instantiateItem(@NonNull ViewGroup container, @NonNull int position)
@NonNull
public boolean isViewFromObject(@NonNull View view, @NonNull Object object)
@NonNull
public void restoreState(@Nullable Parcelable state, @Nullable ClassLoader loader)