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ViewPager

public class ViewPager
extends ViewGroup

java.lang.Object
   ↳ android.view.View
     ↳ android.view.ViewGroup
       ↳ androidx.viewpager.widget.ViewPager

Layout manager that allows the user to flip left and right through pages of data. You supply an implementation of a PagerAdapter to generate the pages that the view shows.

ViewPager is most often used in conjunction with Fragment, which is a convenient way to supply and manage the lifecycle of each page. There are standard adapters implemented for using fragments with the ViewPager, which cover the most common use cases. These are FragmentPagerAdapter and FragmentStatePagerAdapter; each of these classes have simple code showing how to build a full user interface with them.

Views which are annotated with the ViewPager.DecorView annotation are treated as part of the view pagers 'decor'. Each decor view's position can be controlled via its android:layout_gravity attribute. For example: 

 <androidx.viewpager.widget.ViewPager
     android:layout_width="match_parent"
     android:layout_height="match_parent">

     <androidx.viewpager.widget.PagerTitleStrip
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_gravity="top" />

 </androidx.viewpager.widget.ViewPager>

For more information about how to use ViewPager, read Creating Swipe Views with Tabs.

You can find examples of using ViewPager in the API 4+ Support Demos and API 13+ Support Demos sample code.

Summary

Nested classes

@interface ViewPager.DecorView

Annotation which allows marking of views to be decoration views when added to a view pager. 

class ViewPager.LayoutParams

Layout parameters that should be supplied for views added to a ViewPager. 

interface ViewPager.OnAdapterChangeListener

Callback interface for responding to adapter changes. 

interface ViewPager.OnPageChangeListener

Callback interface for responding to changing state of the selected page. 

interface ViewPager.PageTransformer

A PageTransformer is invoked whenever a visible/attached page is scrolled. 

class ViewPager.SavedState

This is the persistent state that is saved by ViewPager. 

class ViewPager.SimpleOnPageChangeListener

Simple implementation of the ViewPager.OnPageChangeListener interface with stub implementations of each method. 

Constants

int SCROLL_STATE_DRAGGING

Indicates that the pager is currently being dragged by the user.

int SCROLL_STATE_IDLE

Indicates that the pager is in an idle, settled state.

int SCROLL_STATE_SETTLING

Indicates that the pager is in the process of settling to a final position.

Inherited constants

Inherited fields

Public constructors

ViewPager(Context context)
ViewPager(Context context, AttributeSet attrs)

Public methods

void addFocusables(ArrayList<View> views, int direction, int focusableMode)

We only want the current page that is being shown to be focusable.

void addOnAdapterChangeListener(ViewPager.OnAdapterChangeListener listener)

Add a listener that will be invoked whenever the adapter for this ViewPager changes.

void addOnPageChangeListener(ViewPager.OnPageChangeListener listener)

Add a listener that will be invoked whenever the page changes or is incrementally scrolled.

void addTouchables(ArrayList<View> views)

We only want the current page that is being shown to be touchable.

void addView(View child, int index, ViewGroup.LayoutParams params)
boolean arrowScroll(int direction)

Handle scrolling in response to a left or right arrow click.

boolean beginFakeDrag()

Start a fake drag of the pager.

boolean canScrollHorizontally(int direction)

Check if this ViewPager can be scrolled horizontally in a certain direction.

void clearOnPageChangeListeners()

Remove all listeners that are notified of any changes in scroll state or position.

void computeScroll()
boolean dispatchKeyEvent(KeyEvent event)
boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event)
void draw(Canvas canvas)
void endFakeDrag()

End a fake drag of the pager.

boolean executeKeyEvent(KeyEvent event)

You can call this function yourself to have the scroll view perform scrolling from a key event, just as if the event had been dispatched to it by the view hierarchy.

void fakeDragBy(float xOffset)

Fake drag by an offset in pixels.

ViewGroup.LayoutParams generateLayoutParams(AttributeSet attrs)
PagerAdapter getAdapter()

Retrieve the current adapter supplying pages.

int getCurrentItem()
int getOffscreenPageLimit()

Returns the number of pages that will be retained to either side of the current page in the view hierarchy in an idle state.

int getPageMargin()

Return the margin between pages.

boolean isFakeDragging()

Returns true if a fake drag is in progress.

boolean onInterceptTouchEvent(MotionEvent ev)
void onRestoreInstanceState(Parcelable state)
Parcelable onSaveInstanceState()
boolean onTouchEvent(MotionEvent ev)
void removeOnAdapterChangeListener(ViewPager.OnAdapterChangeListener listener)

Remove a listener that was previously added via addOnAdapterChangeListener(OnAdapterChangeListener).

void removeOnPageChangeListener(ViewPager.OnPageChangeListener listener)

Remove a listener that was previously added via addOnPageChangeListener(OnPageChangeListener).

void removeView(View view)
void setAdapter(PagerAdapter adapter)

Set a PagerAdapter that will supply views for this pager as needed.

void setCurrentItem(int item)

Set the currently selected page.

void setCurrentItem(int item, boolean smoothScroll)

Set the currently selected page.

void setOffscreenPageLimit(int limit)

Set the number of pages that should be retained to either side of the current page in the view hierarchy in an idle state.

void setOnPageChangeListener(ViewPager.OnPageChangeListener listener)

This method is deprecated. Use addOnPageChangeListener(OnPageChangeListener) and removeOnPageChangeListener(OnPageChangeListener) instead.

void setPageMargin(int marginPixels)

Set the margin between pages.

void setPageMarginDrawable(int resId)

Set a drawable that will be used to fill the margin between pages.

void setPageMarginDrawable(Drawable d)

Set a drawable that will be used to fill the margin between pages.

void setPageTransformer(boolean reverseDrawingOrder, ViewPager.PageTransformer transformer, int pageLayerType)

Sets a ViewPager.PageTransformer that will be called for each attached page whenever the scroll position is changed.

void setPageTransformer(boolean reverseDrawingOrder, ViewPager.PageTransformer transformer)

Sets a ViewPager.PageTransformer that will be called for each attached page whenever the scroll position is changed.

Protected methods

boolean canScroll(View v, boolean checkV, int dx, int x, int y)

Tests scrollability within child views of v given a delta of dx.

boolean checkLayoutParams(ViewGroup.LayoutParams p)
void drawableStateChanged()
ViewGroup.LayoutParams generateDefaultLayoutParams()
ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p)
int getChildDrawingOrder(int childCount, int i)
void onAttachedToWindow()
void onDetachedFromWindow()
void onDraw(Canvas canvas)
void onLayout(boolean changed, int l, int t, int r, int b)
void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
void onPageScrolled(int position, float offset, int offsetPixels)

This method will be invoked when the current page is scrolled, either as part of a programmatically initiated smooth scroll or a user initiated touch scroll.

boolean onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect)

We only want the current page that is being shown to be focusable.

void onSizeChanged(int w, int h, int oldw, int oldh)
boolean verifyDrawable(Drawable who)

Inherited methods

Constants

SCROLL_STATE_DRAGGING

public static final int SCROLL_STATE_DRAGGING

Indicates that the pager is currently being dragged by the user.

Constant Value: 1 (0x00000001)

SCROLL_STATE_IDLE

public static final int SCROLL_STATE_IDLE

Indicates that the pager is in an idle, settled state. The current page is fully in view and no animation is in progress.

Constant Value: 0 (0x00000000)

SCROLL_STATE_SETTLING

public static final int SCROLL_STATE_SETTLING

Indicates that the pager is in the process of settling to a final position.

Constant Value: 2 (0x00000002)

Public constructors

ViewPager

public ViewPager (Context context)

Parameters
context Context

ViewPager

public ViewPager (Context context, 
                AttributeSet attrs)

Parameters
context Context

attrs AttributeSet

Public methods

addFocusables

public void addFocusables (ArrayList<View> views, 
                int direction, 
                int focusableMode)

We only want the current page that is being shown to be focusable.

Parameters
views ArrayList

direction int

focusableMode int

addOnAdapterChangeListener

public void addOnAdapterChangeListener (ViewPager.OnAdapterChangeListener listener)

Add a listener that will be invoked whenever the adapter for this ViewPager changes.

Parameters
listener ViewPager.OnAdapterChangeListener: listener to add

addOnPageChangeListener

public void addOnPageChangeListener (ViewPager.OnPageChangeListener listener)

Add a listener that will be invoked whenever the page changes or is incrementally scrolled. See ViewPager.OnPageChangeListener.

Components that add a listener should take care to remove it when finished. Other components that take ownership of a view may call clearOnPageChangeListeners() to remove all attached listeners.

Parameters
listener ViewPager.OnPageChangeListener: listener to add

addTouchables

public void addTouchables (ArrayList<View> views)

We only want the current page that is being shown to be touchable.

Parameters
views ArrayList

addView

public void addView (View child, 
                int index, 
                ViewGroup.LayoutParams params)

Parameters
child View

index int

params ViewGroup.LayoutParams

arrowScroll

public boolean arrowScroll (int direction)

Handle scrolling in response to a left or right arrow click.

Parameters
direction int: The direction corresponding to the arrow key that was pressed. It should be either View.FOCUS_LEFT or View.FOCUS_RIGHT.
Returns
boolean Whether the scrolling was handled successfully.

beginFakeDrag

public boolean beginFakeDrag ()

Start a fake drag of the pager.

A fake drag can be useful if you want to synchronize the motion of the ViewPager with the touch scrolling of another view, while still letting the ViewPager control the snapping motion and fling behavior. (e.g. parallax-scrolling tabs.) Call fakeDragBy(float) to simulate the actual drag motion. Call endFakeDrag() to complete the fake drag and fling as necessary.

During a fake drag the ViewPager will ignore all touch events. If a real drag is already in progress, this method will return false.

Returns
boolean true if the fake drag began successfully, false if it could not be started.

canScrollHorizontally

public boolean canScrollHorizontally (int direction)

Check if this ViewPager can be scrolled horizontally in a certain direction.

Parameters
direction int: Negative to check scrolling left, positive to check scrolling right.
Returns
boolean Whether this ViewPager can be scrolled in the specified direction. It will always return false if the specified direction is 0.

clearOnPageChangeListeners

public void clearOnPageChangeListeners ()

Remove all listeners that are notified of any changes in scroll state or position.

computeScroll

public void computeScroll ()

dispatchKeyEvent

public boolean dispatchKeyEvent (KeyEvent event)

Parameters
event KeyEvent

Returns
boolean

dispatchPopulateAccessibilityEvent

public boolean dispatchPopulateAccessibilityEvent (AccessibilityEvent event)

Parameters
event AccessibilityEvent

Returns
boolean

draw

public void draw (Canvas canvas)

Parameters
canvas Canvas

endFakeDrag

public void endFakeDrag ()

End a fake drag of the pager.

executeKeyEvent

public boolean executeKeyEvent (KeyEvent event)

You can call this function yourself to have the scroll view perform scrolling from a key event, just as if the event had been dispatched to it by the view hierarchy.

Parameters
event KeyEvent: The key event to execute.
Returns
boolean Return true if the event was handled, else false.

fakeDragBy

public void fakeDragBy (float xOffset)

Fake drag by an offset in pixels. You must have called beginFakeDrag() first.

Parameters
xOffset float: Offset in pixels to drag by.

generateLayoutParams

public ViewGroup.LayoutParams generateLayoutParams (AttributeSet attrs)

Parameters
attrs AttributeSet

Returns
ViewGroup.LayoutParams

getAdapter

public PagerAdapter getAdapter ()

Retrieve the current adapter supplying pages.

Returns
PagerAdapter The currently registered PagerAdapter

getCurrentItem

public int getCurrentItem ()

Returns
int

getOffscreenPageLimit

public int getOffscreenPageLimit ()

Returns the number of pages that will be retained to either side of the current page in the view hierarchy in an idle state. Defaults to 1.

Returns
int How many pages will be kept offscreen on either side

getPageMargin

public int getPageMargin ()

Return the margin between pages.

Returns
int The size of the margin in pixels

isFakeDragging

public boolean isFakeDragging ()

Returns true if a fake drag is in progress.

Returns
boolean true if currently in a fake drag, false otherwise.

onInterceptTouchEvent

public boolean onInterceptTouchEvent (MotionEvent ev)

Parameters
ev MotionEvent

Returns
boolean

onRestoreInstanceState

public void onRestoreInstanceState (Parcelable state)

Parameters
state Parcelable

onSaveInstanceState

public