ScrollView

public class ScrollView
extends FrameLayout

java.lang.Object
   ↳ android.view.View
     ↳ android.view.ViewGroup
       ↳ android.widget.FrameLayout
         ↳ android.widget.ScrollView


A view group that allows the view hierarchy placed within it to be scrolled. Scroll view may have only one direct child placed within it. To add multiple views within the scroll view, make the direct child you add a view group, for example LinearLayout, and place additional views within that LinearLayout.

Scroll view supports vertical scrolling only. For horizontal scrolling, use HorizontalScrollView instead.

Never add a RecyclerView or ListView to a scroll view. Doing so results in poor user interface performance and a poor user experience.

For vertical scrolling, consider NestedScrollView instead of scroll view which offers greater user interface flexibility and support for the material design scrolling patterns.

Material Design offers guidelines on how the appearance of several UI components, including app bars and banners, should respond to gestures.

Summary

XML attributes

android:fillViewport Defines whether the scrollview should stretch its content to fill the viewport. 

Inherited XML attributes

Inherited constants

Inherited fields

Public constructors

ScrollView(Context context)
ScrollView(Context context, AttributeSet attrs)
ScrollView(Context context, AttributeSet attrs, int defStyleAttr)
ScrollView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)

Public methods

void addView(View child, int index)

Adds a child view.

void addView(View child, ViewGroup.LayoutParams params)

Adds a child view with the specified layout parameters.

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

Adds a child view with the specified layout parameters.

void addView(View child)

Adds a child view.

boolean arrowScroll(int direction)

Handle scrolling in response to an up or down arrow click.

void computeScroll()

Called by a parent to request that a child update its values for mScrollX and mScrollY if necessary.

boolean dispatchKeyEvent(KeyEvent event)

Dispatch a key event to the next view on the focus path.

void draw(Canvas canvas)

Manually render this view (and all of its children) to the given Canvas.

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 fling(int velocityY)

Fling the scroll view

boolean fullScroll(int direction)

Handles scrolling in response to a "home/end" shortcut press.

CharSequence getAccessibilityClassName()

Return the class name of this object to be used for accessibility purposes.

int getBottomEdgeEffectColor()

Returns the bottom edge effect color.

int getMaxScrollAmount()
int getTopEdgeEffectColor()

Returns the top edge effect color.

boolean isFillViewport()

Indicates whether this ScrollView's content is stretched to fill the viewport.

boolean isSmoothScrollingEnabled()
boolean onGenericMotionEvent(MotionEvent event)

Implement this method to handle generic motion events.

boolean onInterceptTouchEvent(MotionEvent ev)

Implement this method to intercept all touch screen motion events.

boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed)

Request a fling from a nested scroll.

void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed)

React to a nested scroll in progress.

void onNestedScrollAccepted(View child, View target, int axes)

React to the successful claiming of a nested scroll operation.

boolean onStartNestedScroll(View child, View target, int nestedScrollAxes)

React to a descendant view initiating a nestable scroll operation, claiming the nested scroll operation if appropriate.

void onStopNestedScroll(View target)

React to a nested scroll operation ending.

boolean onTouchEvent(MotionEvent ev)

Implement this method to handle touch screen motion events.

boolean pageScroll(int direction)

Handles scrolling in response to a "page up/down" shortcut press.

void requestChildFocus(View child, View focused)

Called when a child of this parent wants focus

boolean requestChildRectangleOnScreen(View child, Rect rectangle, boolean immediate)

Called when a child of this group wants a particular rectangle to be positioned onto the screen.

void requestDisallowInterceptTouchEvent(boolean disallowIntercept)

Called when a child does not want this parent and its ancestors to intercept touch events with ViewGroup#onInterceptTouchEvent(MotionEvent).

void requestLayout()

Call this when something has changed which has invalidated the layout of this view.

void scrollTo(int x, int y)

Set the scrolled position of your view.

This version also clamps the scrolling to the bounds of our child.

void scrollToDescendant(View child)

Scrolls the view to the given child.

void setBottomEdgeEffectColor(int color)

Sets the bottom edge effect color.

void setEdgeEffectColor(int color)

Sets the edge effect color for both top and bottom edge effects.

void setFillViewport(boolean fillViewport)

Indicates this ScrollView whether it should stretch its content height to fill the viewport or not.

void setSmoothScrollingEnabled(boolean smoothScrollingEnabled)

Set whether arrow scrolling will animate its transition.

void setTopEdgeEffectColor(int color)

Sets the top edge effect color.

boolean shouldDelayChildPressedState()

Return true if the pressed state should be delayed for children or descendants of this ViewGroup.

final void smoothScrollBy(int dx, int dy)

Like View#scrollBy, but scroll smoothly instead of immediately.

final void smoothScrollTo(int x, int y)

Like scrollTo(int, int), but scroll smoothly instead of immediately.

Protected methods

int computeScrollDeltaToGetChildRectOnScreen(Rect rect)

Compute the amount to scroll in the Y direction in order to get a rectangle completely on the screen (or, if taller than the screen, at least the first screen size chunk of it).

int computeVerticalScrollOffset()

Compute the vertical offset of the vertical scrollbar's thumb within the horizontal range.

int computeVerticalScrollRange()

The scroll range of a scroll view is the overall height of all of its children.

float getBottomFadingEdgeStrength()

Returns the strength, or intensity, of the bottom faded edge.

float getTopFadingEdgeStrength()

Returns the strength, or intensity, of the top faded edge.

void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec)

Ask one of the children of this view to measure itself, taking into account both the MeasureSpec requirements for this view and its padding.

void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed)

Ask one of the children of this view to measure itself, taking into account both the MeasureSpec requirements for this view and its padding and margins.

void onDetachedFromWindow()

This is called when the view is detached from a window.

void onLayout(boolean changed, int l, int t, int r, int b)

Called from layout when this view should assign a size and position to each of its children.

void onMeasure(int widthMeasureSpec, int heightMeasureSpec)

Measure the view and its content to determine the measured width and the measured height.

void onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY)

Called by overScrollBy(int, int, int, int, int, int, int, int, boolean) to respond to the results of an over-scroll operation.

boolean onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect)

When looking for focus in children of a scroll view, need to be a little more careful not to give focus to something that is scrolled off screen.

void onRestoreInstanceState(Parcelable state)

Hook allowing a view to re-apply a representation of its internal state that had previously been generated by onSaveInstanceState().

Parcelable onSaveInstanceState()

Hook allowing a view to generate a representation of its internal state that can later be used to create a new instance with that same state.

void onSizeChanged(int w, int h, int oldw, int oldh)

This is called during layout when the size of this view has changed.

Inherited methods

XML attributes

android:fillViewport

Defines whether the scrollview should stretch its content to fill the viewport.

May be a boolean value, such as "true" or "false".

Related methods:

Public constructors

ScrollView

Added in API level 1
public ScrollView (Context context)

Parameters
context Context

ScrollView

Added in API level 1
public ScrollView (Context context, 
                AttributeSet attrs)

Parameters
context Context

attrs AttributeSet

ScrollView

Added in API level 1
public ScrollView (Context context, 
                AttributeSet attrs, 
                int defStyleAttr)

Parameters
context Context

attrs AttributeSet

defStyleAttr int

ScrollView

Added in API level 1
public ScrollView (Context context, 
                AttributeSet attrs, 
                int defStyleAttr, 
                int defStyleRes)

Parameters
context Context

attrs AttributeSet

defStyleAttr int

defStyleRes int

Public methods

addView

Added in API level 1
public void addView (View child, 
                int index)

Adds a child view. If no layout parameters are already set on the child, the default parameters for this ViewGroup are set on the child.

Note: do not invoke this method from View.draw(android.graphics.Canvas), View.onDraw(android.graphics.Canvas), dispatchDraw(android.graphics.Canvas) or any related method.

Parameters
child View: the child view to add

index int: the position at which to add the child

addView

Added in API level 1
public void addView (View child, 
                ViewGroup.LayoutParams params)

Adds a child view with the specified layout parameters.

Note: do not invoke this method from View.draw(android.graphics.Canvas), View.onDraw(android.graphics.Canvas), dispatchDraw(android.graphics.Canvas) or any related method.

Parameters
child View: the child view to add

params ViewGroup.LayoutParams: the layout parameters to set on the child

addView

Added in API level 1
public void addView (View child, 
                int index, 
                ViewGroup.LayoutParams params)

Adds a child view with the specified layout parameters.

Note: do not invoke this method from View.draw(android.graphics.Canvas), View.onDraw(android.graphics.Canvas), dispatchDraw(android.graphics.Canvas) or any related method.

Parameters
child View: the child view to add

index int: the position at which to add the child or -1 to add last

params ViewGroup.LayoutParams: the layout parameters to set on the child

addView

Added in API level 1
public void addView (View child)

Adds a child view. If no layout parameters are already set on the child, the default parameters for this ViewGroup are set on the child.

Note: do not invoke this method from View.draw(android.graphics.Canvas), View.onDraw(android.graphics.Canvas), dispatchDraw(android.graphics.Canvas) or any related method.

Parameters
child View: the child view to add

arrowScroll

Added in API level 1
public boolean arrowScroll (int direction)

Handle scrolling in response to an up or down arrow click.

Parameters
direction int: The direction corresponding to the arrow key that was pressed

Returns
boolean True if we consumed the event, false otherwise

computeScroll

Added in API level 1
public void computeScroll ()

Called by a parent to request that a child update its values for mScrollX and mScrollY if necessary. This will typically be done if the child is animating a scroll using a Scroller object.

dispatchKeyEvent

Added in API level 1
public boolean dispatchKeyEvent (KeyEvent event)

Dispatch a key event to the next view on the focus path. This path runs from the top of the view tree down to the currently focused view. If this view has focus, it will dispatch to itself. Otherwise it will dispatch the next node down the focus path. This method also fires any key listeners.

Parameters
event KeyEvent: The key event to be dispatched.

Returns
boolean True if the event was handled, false otherwise.

draw

Added in API level 1
public void draw (Canvas canvas)

Manually render this view (and all of its children) to the given Canvas. The view must have already done a full layout before this function is called. When implementing a view, implement onDraw(android.graphics.Canvas) instead of overriding this method. If you do need to override this method, call the superclass version.
If you override this method you must call through to the superclass implementation.

Parameters
canvas Canvas: The Canvas to which the View is rendered. This value cannot be null.

executeKeyEvent

Added in API level 1
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.

fling

Added in API level 1
public void fling (int velocityY)

Fling the scroll view

Parameters
velocityY int: The initial velocity in the Y direction. Positive numbers mean that the finger/cursor is moving down the screen, which means we want to scroll towards the top.

fullScroll

Added in API level 1
public boolean fullScroll (int direction)

Handles scrolling in response to a "home/end" shortcut press. This method will scroll the view to the top or bottom and give the focus to the topmost/bottommost component in the new visible area. If no component is a good candidate for focus, this scrollview reclaims the focus.

Parameters
direction int: the scroll direction: View.FOCUS_UP to go the top of the view or View.FOCUS_DOWN to go the bottom

Returns
boolean true if the key event is consumed by this method, false otherwise

getAccessibilityClassName

Added in API level 23
public CharSequence getAccessibilityClassName ()

Return the class name of this object to be used for accessibility purposes. Subclasses should only override this if they are implementing something that should be seen as a completely new class of view when used by accessibility, unrelated to the class it is deriving from. This is used to fill in AccessibilityNodeInfo.setClassName.

Returns
CharSequence

getBottomEdgeEffectColor

Added in API level 29
public int getBottomEdgeEffectColor ()

Returns the bottom edge effect color.

Returns
int The bottom edge effect color.

getMaxScrollAmount

Added in API level 1
public int getMaxScrollAmount ()

Returns
int The maximum amount this scroll view will scroll in response to an arrow event.

getTopEdgeEffectColor

Added in API level 29
public int getTopEdgeEffectColor ()

Returns the top edge effect color.

Returns
int The top edge effect color.

isFillViewport

Added in API level 1
public boolean isFillViewport ()

Indicates whether this ScrollView's content is stretched to fill the viewport.

Related XML Attributes:

Returns
boolean True if the content fills the viewport, false otherwise.

isSmoothScrollingEnabled

Added in API level 1
public boolean isSmoothScrollingEnabled ()

Returns
boolean Whether arrow scrolling will animate its transition.

onGenericMotionEvent

Added in API level 12
public boolean onGenericMotionEvent (MotionEvent event)

Implement this method to handle generic motion events.

Generic motion events describe joystick movements, hover events from mouse or stylus devices, trackpad touches, scroll wheel movements and other motion events not handled by onTouchEvent(android.view.MotionEvent) or onTrackballEvent(android.view.MotionEvent). The source of the motion event specifies the class of input that was received. Implementations of this method must examine the bits in the source before processing the event. The following code example shows how this is done.

Generic motion events with source class InputDevice#SOURCE_CLASS_POINTER are delivered to the view under the pointer. All other generic motion events are delivered to the focused view.

 public boolean onGenericMotionEvent(MotionEvent event) {
     if (event.isFromSource(InputDevice.SOURCE_CLASS_JOYSTICK)) {
         if (event.getAction() == MotionEvent.ACTION_MOVE) {
             // process the joystick movement...
             return true;
         }
     }
     if (event.isFromSource(InputDevice.SOURCE_CLASS_POINTER)) {
         switch (event.getAction()) {
             case MotionEvent.ACTION_HOVER_MOVE:
                 // process the hover movement...
                 return true;
             case MotionEvent.ACTION_SCROLL:
                 // process the scroll wheel movement...
                 return true;
         }
     }
     return super.onGenericMotionEvent(event);
 }

Parameters
event MotionEvent: The generic motion event being processed.

Returns
boolean True if the event was handled, false otherwise.

onInterceptTouchEvent

Added in API level 1
public boolean onInterceptTouchEvent (MotionEvent ev)

Implement this method to intercept all touch screen motion events. This allows you to watch events as they are dispatched to your children, and take ownership of the current gesture at any point.

Using this function takes some care, as it has a fairly complicated interaction with View.onTouchEvent(MotionEvent), and using it requires implementing that method as well as this one in the correct way. Events will be received in the following order:

  1. You will receive the down event here.
  2. The down event will be handled either by a child of this view group, or given to your own onTouchEvent() method to handle; this means you should implement onTouchEvent() to return true, so you will continue to see the rest of the gesture (instead of looking for a parent view to handle it). Also, by returning true from onTouchEvent(), you will not receive any following events in onInterceptTouchEvent() and all touch processing must happen in onTouchEvent() like normal.
  3. For as long as you return false from this function, each following event (up to and including the final up) will be delivered first here and then to the target's onTouchEvent().
  4. If you return true from here, you will not receive any following events: the target view will receive the same event but with the action MotionEvent#ACTION_CANCEL, and all further events will be delivered to your onTouchEvent() method and no longer appear here.

Parameters
ev MotionEvent: The motion event being dispatched down the hierarchy.

Returns
boolean Return true to steal motion events from the children and have them dispatched to this ViewGroup through onTouchEvent(). The current target will receive an ACTION_CANCEL event, and no further messages will be delivered here.

onNestedFling

public boolean onNestedFling (View target, 
                float velocityX, 
                float velocityY, 
                boolean consumed)

Request a fling from a nested scroll.

This method signifies that a nested scrolling child has detected suitable conditions for a fling. Generally this means that a touch scroll has ended with a velocity in the direction of scrolling that meets or exceeds the minimum fling velocity along a scrollable axis.

If a nested scrolling child view would normally fling but it is at the edge of its own content, it can use this method to delegate the fling to its nested scrolling parent instead. The parent may optionally consume the fling or observe a child fling.

Parameters
target View: View that initiated the nested scroll This value cannot be null.

velocityX float: Horizontal velocity in pixels per second

velocityY float: Vertical velocity in pixels per second

consumed boolean: true if the child consumed the fling, false otherwise

Returns
boolean true if this parent consumed or otherwise reacted to the fling

onNestedScroll

Added in API level 21
public void onNestedScroll (View target, 
                int dxConsumed, 
                int dyConsumed, 
                int dxUnconsumed, 
                int dyUnconsumed)

React to a nested scroll in progress.

This method will be called when the ViewParent's current nested scrolling child view dispatches a nested scroll event. To receive calls to this method the ViewParent must have previously returned true for a call to onStartNestedScroll(android.view.View, android.view.View, int).

Both the consumed and unconsumed portions of the scroll distance are reported to the ViewParent. An implementation may choose to use the consumed portion to match or chase scroll position of multiple child elements, for example. The unconsumed portion may be used to allow continuous dragging of multiple scrolling or draggable elements, such as scrolling a list within a vertical drawer where the drawer begins dragging once the edge of inner scrolling content is reached.

Parameters
target View: The descendent view controlling the nested scroll This value cannot be null.

dxConsumed int: Horizontal scroll distance in pixels already consumed by target

dyConsumed int: Vertical scroll distance in pixels already consumed by target

dxUnconsumed int: Horizontal scroll distance in pixels not consumed by target

dyUnconsumed int: Vertical scroll distance in pixels not consumed by target

onNestedScrollAccepted

Added in API level 21
public void onNestedScrollAccepted (View child, 
                View target, 
                int axes)

React to the successful claiming of a nested scroll operation.

This method will be called after onStartNestedScroll returns true. It offers an opportunity for the view and its superclasses to perform initial configuration for the nested scroll. Implementations of this method should always call their superclass's implementation of this method if one is present.

Parameters
child View: Direct child of this ViewParent containing target This value cannot be null.

target View: View that initiated the nested scroll This value cannot be null.

axes int: Flags consisting of View#SCROLL_AXIS_HORIZONTAL, View#SCROLL_AXIS_VERTICAL or both

onStartNestedScroll

Added in API level 21
public boolean onStartNestedScroll (View child, 
                View target, 
                int nestedScrollAxes)

React to a descendant view initiating a nestable scroll operation, claiming the nested scroll operation if appropriate.

This method will be called in response to a descendant view invoking View#startNestedScroll(int). Each parent up the view hierarchy will be given an opportunity to respond and claim the nested scrolling operation by returning true.

This method may be overridden by ViewParent implementations to indicate when the view is willing to support a nested scrolling operation that is about to begin. If it returns true, this ViewParent will become the target view's nested scrolling parent for the duration of the scroll operation in progress. When the nested scroll is finished this ViewParent will receive a call to onStopNestedScroll(android.view.View).

Parameters
child View: Direct child of this ViewParent containing target This value cannot be null.

target View: View that initiated the nested scroll This value cannot be null.

nestedScrollAxes int: Flags consisting of View#SCROLL_AXIS_HORIZONTAL, View#SCROLL_AXIS_VERTICAL or both

Returns
boolean true if this ViewParent accepts the nested scroll operation

onStopNestedScroll

public void onStopNestedScroll (View target)

React to a nested scroll operation ending.

Perform cleanup after a nested scrolling operation. This method will be called when a nested scroll stops, for example when a nested touch scroll ends with a MotionEvent#ACTION_UP or MotionEvent#ACTION_CANCEL event. Implementations of this method should always call their superclass's implementation of this method if one is present.

Parameters
target View: View that initiated the nested scroll This value cannot be null.

onTouchEvent

Added in API level 1
public boolean onTouchEvent (MotionEvent ev)

Implement this method to handle touch screen motion events.

If this method is used to detect click actions, it is recommended that the actions be performed by implementing and calling performClick(). This will ensure consistent system behavior, including:

  • obeying click sound preferences
  • dispatching OnClickListener calls
  • handling ACTION_CLICK when accessibility features are enabled

Parameters
ev MotionEvent: The motion event.

Returns
boolean True if the event was handled, false otherwise.

pageScroll

Added in API level 1
public boolean pageScroll (int direction)

Handles scrolling in response to a "page up/down" shortcut press. This method will scroll the view by one page up or down and give the focus to the topmost/bottommost component in the new visible area. If no component is a good candidate for focus, this scrollview reclaims the focus.

Parameters
direction int: the scroll direction: View.FOCUS_UP to go one page up or View.FOCUS_DOWN to go one page down

Returns
boolean true if the key event is consumed by this method, false otherwise

requestChildFocus

Added in API level 1
public void requestChildFocus (View child, 
                View focused)

Called when a child of this parent wants focus

Parameters
child View: The child of this ViewParent that wants focus. This view will contain the focused view. It is not necessarily the view that actually has focus.

focused View: The view that is a descendant of child that actually has focus

requestChildRectangleOnScreen

Added in API level 1
public boolean requestChildRectangleOnScreen (View child, 
                Rect rectangle, 
                boolean immediate)

Called when a child of this group wants a particular rectangle to be positioned onto the screen. ViewGroups overriding this can trust that:

  • child will be a direct child of this group
  • rectangle will be in the child's content coordinates

ViewGroups overriding this should uphold the contract:

  • nothing will change if the rectangle is already visible
  • the view port will be scrolled only just enough to make the rectangle visible
    • Parameters
      child View: The direct child making the request. This value cannot be null.

      rectangle Rect: The rectangle in the child's coordinates the child wishes to be on the screen.

      immediate boolean: True to forbid animated or delayed scrolling, false otherwise

      Returns
      boolean Whether the group scrolled to handle the operation

requestDisallowInterceptTouchEvent

Added in API level 1
public void requestDisallowInterceptTouchEvent (boolean disallowIntercept)

Called when a child does not want this parent and its ancestors to intercept touch events with ViewGroup#onInterceptTouchEvent(MotionEvent).

This parent should pass this call onto its parents. This parent must obey this request for the duration of the touch (that is, only clear the flag after this parent has received an up or a cancel.

Parameters
disallowIntercept boolean: True if the child does not want the parent to intercept touch events.

requestLayout

Added in API level 1
public void requestLayout ()

Call this when something has changed which has invalidated the layout of this view. This will schedule a layout pass of the view tree. This should not be called while the view hierarchy is currently in a layout pass (isInLayout(). If layout is happening, the request may be honored at the end of the current layout pass (and then layout will run again) or after the current frame is drawn and the next layout occurs.

Subclasses which override this method should call the superclass method to handle possible request-during-layout errors correctly.


If you override this method you must call through to the superclass implementation.

scrollTo

Added in API level 1
public void scrollTo (int x, 
                int y)

Set the scrolled position of your view. This will cause a call to onScrollChanged(int, int, int, int) and the view will be invalidated.

This version also clamps the scrolling to the bounds of our child.

Parameters
x int: the x position to scroll to

y int: the y position to scroll to

scrollToDescendant

Added in API level 29
public void scrollToDescendant (View child)

Scrolls the view to the given child.

Parameters
child View: the View to scroll to This value cannot be null.

setBottomEdgeEffectColor

Added in API level 29
public void setBottomEdgeEffectColor (int color)

Sets the bottom edge effect color.

Parameters
color int: The color for the bottom edge effect.

setEdgeEffectColor

Added in API level 29
public void setEdgeEffectColor (int color)

Sets the edge effect color for both top and bottom edge effects.

Parameters
color int: The color for the edge effects.

setFillViewport

Added in API level 1
public void setFillViewport (boolean fillViewport)

Indicates this ScrollView whether it should stretch its content height to fill the viewport or not.

Related XML Attributes:

Parameters
fillViewport boolean: True to stretch the content's height to the viewport's boundaries, false otherwise.

setSmoothScrollingEnabled

Added in API level 1
public void setSmoothScrollingEnabled (boolean smoothScrollingEnabled)

Set whether arrow scrolling will animate its transition.

Parameters
smoothScrollingEnabled boolean: whether arrow scrolling will animate its transition

setTopEdgeEffectColor

Added in API level 29
public void setTopEdgeEffectColor (int color)

Sets the top edge effect color.

Parameters
color int: The color for the top edge effect.

shouldDelayChildPressedState

Added in API level 14
public boolean shouldDelayChildPressedState ()

Return true if the pressed state should be delayed for children or descendants of this ViewGroup. Generally, this should be done for containers that can scroll, such as a List. This prevents the pressed state from appearing when the user is actually trying to scroll the content. The default implementation returns true for compatibility reasons. Subclasses that do not scroll should generally override this method and return false.

Returns
boolean

smoothScrollBy

Added in API level 1
public final void smoothScrollBy (int dx, 
                int dy)

Like View#scrollBy, but scroll smoothly instead of immediately.

Parameters
dx int: the number of pixels to scroll by on the X axis

dy int: the number of pixels to scroll by on the Y axis

smoothScrollTo

Added in API level 1
public final void smoothScrollTo (int x, 
                int y)

Like scrollTo(int, int), but scroll smoothly instead of immediately.

Parameters
x int: the position where to scroll on the X axis

y int: the position where to scroll on the Y axis

Protected methods

computeScrollDeltaToGetChildRectOnScreen

Added in API level 1
protected int computeScrollDeltaToGetChildRectOnScreen (Rect rect)

Compute the amount to scroll in the Y direction in order to get a rectangle completely on the screen (or, if taller than the screen, at least the first screen size chunk of it).

Parameters
rect Rect: The rect.

Returns
int The scroll delta.

computeVerticalScrollOffset

Added in API level 1
protected int computeVerticalScrollOffset ()

Compute the vertical offset of the vertical scrollbar's thumb within the horizontal range. This value is used to compute the position of the thumb within the scrollbar's track.

The range is expressed in arbitrary units that must be the same as the units used by computeVerticalScrollRange() and computeVerticalScrollExtent().

The default offset is the scroll offset of this view.

Returns
int the vertical offset of the scrollbar's thumb

computeVerticalScrollRange

Added in API level 1
protected int computeVerticalScrollRange ()

The scroll range of a scroll view is the overall height of all of its children.

Returns
int the total vertical range represented by the vertical scrollbar

The default range is the drawing height of this view.

getBottomFadingEdgeStrength

Added in API level 1
protected float getBottomFadingEdgeStrength ()

Returns the strength, or intensity, of the bottom faded edge. The strength is a value between 0.0 (no fade) and 1.0 (full fade). The default implementation returns 0.0 or 1.0 but no value in between. Subclasses should override this method to provide a smoother fade transition when scrolling occurs.

Returns
float the intensity of the bottom fade as a float between 0.0f and 1.0f

getTopFadingEdgeStrength

Added in API level 1
protected float getTopFadingEdgeStrength ()

Returns the strength, or intensity, of the top faded edge. The strength is a value between 0.0 (no fade) and 1.0 (full fade). The default implementation returns 0.0 or 1.0 but no value in between. Subclasses should override this method to provide a smoother fade transition when scrolling occurs.

Returns
float the intensity of the top fade as a float between 0.0f and 1.0f

measureChild

Added in API level 1
protected void measureChild (View child, 
                int parentWidthMeasureSpec, 
                int parentHeightMeasureSpec)

Ask one of the children of this view to measure itself, taking into account both the MeasureSpec requirements for this view and its padding. The heavy lifting is done in getChildMeasureSpec.

Parameters
child View: The child to measure

parentWidthMeasureSpec int: The width requirements for this view

parentHeightMeasureSpec int: The height requirements for this view

measureChildWithMargins

Added in API level 1
protected void measureChildWithMargins (View child, 
                int parentWidthMeasureSpec, 
                int widthUsed, 
                int parentHeightMeasureSpec, 
                int heightUsed)

Ask one of the children of this view to measure itself, taking into account both the MeasureSpec requirements for this view and its padding and margins. The child must have MarginLayoutParams The heavy lifting is done in getChildMeasureSpec.

Parameters
child View: The child to measure

parentWidthMeasureSpec int: The width requirements for this view

widthUsed int: Extra space that has been used up by the parent horizontally (possibly by other children of the parent)

parentHeightMeasureSpec int: The height requirements for this view

heightUsed int: Extra space that has been used up by the parent vertically (possibly by other children of the parent)

onDetachedFromWindow

Added in API level 1
protected void onDetachedFromWindow ()

This is called when the view is detached from a window. At this point it no longer has a surface for drawing.
If you override this method you must call through to the superclass implementation.

onLayout

Added in API level 1
protected void onLayout (boolean changed, 
                int l, 
                int t, 
                int r, 
                int b)

Called from layout when this view should assign a size and position to each of its children. Derived classes with children should override this method and call layout on each of their children.

Parameters
changed boolean: This is a new size or position for this view

l int: Left position, relative to parent

t int: Top position, relative to parent

r int: Right position, relative to parent

b int: Bottom position, relative to parent

onMeasure

Added in API level 1
protected void onMeasure (int widthMeasureSpec, 
                int heightMeasureSpec)

Measure the view and its content to determine the measured width and the measured height. This method is invoked by measure(int, int) and should be overridden by subclasses to provide accurate and efficient measurement of their contents.

CONTRACT: When overriding this method, you must call setMeasuredDimension(int, int) to store the measured width and height of this view. Failure to do so will trigger an IllegalStateException, thrown by measure(int, int). Calling the superclass' onMeasure(int, int) is a valid use.

The base class implementation of measure defaults to the background size, unless a larger size is allowed by the MeasureSpec. Subclasses should override onMeasure(int, int) to provide better measurements of their content.

If this method is overridden, it is the subclass's responsibility to make sure the measured height and width are at least the view's minimum height and width (getSuggestedMinimumHeight() and getSuggestedMinimumWidth()).

Parameters
widthMeasureSpec int: horizontal space requirements as imposed by the parent. The requirements are encoded with View.MeasureSpec.

heightMeasureSpec int: vertical space requirements as imposed by the parent. The requirements are encoded with View.MeasureSpec.

onOverScrolled

Added in API level 9
protected void onOverScrolled (int scrollX, 
                int scrollY, 
                boolean clampedX, 
                boolean clampedY)

Called by overScrollBy(int, int, int, int, int, int, int, int, boolean) to respond to the results of an over-scroll operation.

Parameters
scrollX int: New X scroll value in pixels

scrollY int: New Y scroll value in pixels

clampedX boolean: True if scrollX was clamped to an over-scroll boundary

clampedY boolean: True if scrollY was clamped to an over-scroll boundary

onRequestFocusInDescendants

Added in API level 1
protected boolean onRequestFocusInDescendants (int direction, 
                Rect previouslyFocusedRect)

When looking for focus in children of a scroll view, need to be a little more careful not to give focus to something that is scrolled off screen. This is more expensive than the default ViewGroup implementation, otherwise this behavior might have been made the default.

Parameters
direction int: One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and FOCUS_RIGHT

previouslyFocusedRect Rect: The rectangle (in this View's coordinate system) to give a finer grained hint about where focus is coming from. May be null if there is no hint.

Returns
boolean Whether focus was taken.

onRestoreInstanceState

Added in API level 1
protected void onRestoreInstanceState (Parcelable state)

Hook allowing a view to re-apply a representation of its internal state that had previously been generated by onSaveInstanceState(). This function will never be called with a null state.
If you override this method you must call through to the superclass implementation.

Parameters
state Parcelable: The frozen state that had previously been returned by onSaveInstanceState().

onSaveInstanceState

Added in API level 1
protected Parcelable onSaveInstanceState ()

Hook allowing a view to generate a representation of its internal state that can later be used to create a new instance with that same state. This state should only contain information that is not persistent or can not be reconstructed later. For example, you will never store your current position on screen because that will be computed again when a new instance of the view is placed in its view hierarchy.

Some examples of things you may store here: the current cursor position in a text view (but usually not the text itself since that is stored in a content provider or other persistent storage), the currently selected item in a list view.
If you override this method you must call through to the superclass implementation.

Returns
Parcelable Returns a Parcelable object containing the view's current dynamic state, or null if there is nothing interesting to save.

onSizeChanged

Added in API level 1
protected void onSizeChanged (int w, 
                int h, 
                int oldw, 
                int oldh)

This is called during layout when the size of this view has changed. If you were just added to the view hierarchy, you're called with the old values of 0.

Parameters
w int: Current width of this view.

h int: Current height of this view.

oldw int: Old width of this view.

oldh int: Old height of this view.