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.
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 |
const Int |
This property is deprecated. This behavior relies on the deprecated |
Public constructors |
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|
This function is deprecated. use |
FragmentStatePagerAdapter(fm: FragmentManager, behavior: Int)Constructor for |
Public functions |
|
|---|---|
Unit |
destroyItem(container: ViewGroup, position: Int, object: Any)Remove a page for the given position. |
Unit |
finishUpdate(container: ViewGroup)Called when the a change in the shown pages has been completed. |
abstract Fragment |
Return the Fragment associated with a specified position. |
Any |
instantiateItem(container: ViewGroup, position: Int)Create the page for the given position. |
Boolean |
isViewFromObject(view: View, object: Any)Determines whether a page View is associated with a specific key object as returned by |
Unit |
restoreState(state: Parcelable?, loader: ClassLoader?)Restore any instance state associated with this adapter and its pages that was previously saved by |
Parcelable? |
Save any instance state associated with this adapter and its pages that should be restored if the current UI state needs to be reconstructed. |
Unit |
setPrimaryItem(container: ViewGroup, position: Int, object: Any)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. |
Unit |
startUpdate(container: ViewGroup)Called when a change in the shown pages is going to start being made. |
Inherited Constants |
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Inherited functions |
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Constants
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 |
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(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(fm: FragmentManager, 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 |
behavior: Int |
determines if only current fragments are in a resumed state |
Public functions
destroyItem
fun destroyItem(container: ViewGroup, position: Int, object: Any): Unit
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.
| Parameters | |
|---|---|
container: ViewGroup |
The containing View from which the page will be removed. |
position: Int |
The page position to be removed. |
object: Any |
The same object that was returned by |
finishUpdate
fun finishUpdate(container: ViewGroup): Unit
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 | |
|---|---|
container: ViewGroup |
The containing View which is displaying this adapter's page views. |
abstract fun getItem(position: Int): Fragment
Return the Fragment associated with a specified position.
instantiateItem
fun instantiateItem(container: ViewGroup, position: Int): Any
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.
| Parameters | |
|---|---|
container: ViewGroup |
The containing View in which the page will be shown. |
position: Int |
The page position to be instantiated. |
| Returns | |
|---|---|
Any |
Returns an Object representing the new page. This does not need to be a View, but can be some other container of the page. |
fun isViewFromObject(view: View, object: Any): Boolean
Determines whether a page View is associated with a specific key object as returned by instantiateItem. This method is required for a PagerAdapter to function properly.
| Parameters | |
|---|---|
view: View |
Page View to check for association with |
object: Any |
Object to check for association with |
| Returns | |
|---|---|
Boolean |
true if |
restoreState
fun restoreState(state: Parcelable?, loader: ClassLoader?): Unit
Restore any instance state associated with this adapter and its pages that was previously saved by saveState.
| Parameters | |
|---|---|
state: Parcelable? |
State previously saved by a call to |
loader: ClassLoader? |
A ClassLoader that should be used to instantiate any restored objects |
saveState
fun saveState(): Parcelable?
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 | |
|---|---|
Parcelable? |
Saved state for this adapter |
setPrimaryItem
fun setPrimaryItem(container: ViewGroup, position: Int, object: Any): Unit
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. This method will not be invoked when the adapter contains no items.
| Parameters | |
|---|---|
container: ViewGroup |
The containing View from which the page will be removed. |
position: Int |
The page position that is now the primary. |
object: Any |
The same object that was returned by |
startUpdate
fun startUpdate(container: ViewGroup): Unit
Called when a change in the shown pages is going to start being made.
| Parameters | |
|---|---|
container: ViewGroup |
The containing View which is displaying this adapter's page views. |