Android APIs
public class

ScrollView

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

Class Overview

Layout container for a view hierarchy that can be scrolled by the user, allowing it to be larger than the physical display. A ScrollView is a FrameLayout, meaning you should place one child in it containing the entire contents to scroll; this child may itself be a layout manager with a complex hierarchy of objects. A child that is often used is a LinearLayout in a vertical orientation, presenting a vertical array of top-level items that the user can scroll through.

You should never use a ScrollView with a ListView, because ListView takes care of its own vertical scrolling. Most importantly, doing this defeats all of the important optimizations in ListView for dealing with large lists, since it effectively forces the ListView to display its entire list of items to fill up the infinite container supplied by ScrollView.

The TextView class also takes care of its own scrolling, so does not require a ScrollView, but using the two together is possible to achieve the effect of a text view within a larger container.

ScrollView only supports vertical scrolling. For horizontal scrolling, use HorizontalScrollView.

Summary

XML Attributes
Attribute Name Related Method Description
android:fillViewport setFillViewport(boolean) Defines whether the scrollview should stretch its content to fill the viewport. 
[Expand]
Inherited XML Attributes
From class android.widget.FrameLayout
From class android.view.ViewGroup
From class android.view.View
[Expand]
Inherited Constants
From class android.view.ViewGroup
From class android.view.View
[Expand]
Inherited Fields
From class android.view.View
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, int index, ViewGroup.LayoutParams params)
Adds a child view with the specified layout parameters.
void addView(View child)

Adds a child view.

void addView(View child, ViewGroup.LayoutParams params)
Adds a child view with the specified layout parameters.
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.

int getMaxScrollAmount()
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.
void onInitializeAccessibilityEvent(AccessibilityEvent event)
Initializes an AccessibilityEvent with information about this View which is the event source.
void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info)
Initializes an AccessibilityNodeInfo with information about this view.
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.

boolean performAccessibilityAction(int action, Bundle arguments)
Performs the specified accessibility action on the view.
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 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 setFillViewport(boolean fillViewport)
Indicates this ScrollView whether it should stretch its content height to fill the viewport or not.
void setOverScrollMode(int mode)
Set the over-scroll mode for this view.
void setSmoothScrollingEnabled(boolean smoothScrollingEnabled)
Set whether arrow scrolling will animate its transition.
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 scrollBy(int, int), 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.
[Expand]
Inherited Methods
From class android.widget.FrameLayout
From class android.view.ViewGroup
From class android.view.View
From class java.lang.Object
From interface android.graphics.drawable.Drawable.Callback
From interface android.view.KeyEvent.Callback
From interface android.view.ViewManager
From interface android.view.ViewParent
From interface android.view.accessibility.AccessibilityEventSource

XML Attributes

android:fillViewport

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

Must be a boolean value, either "true" or "false".

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

This corresponds to the global attribute resource symbol fillViewport.

Related Methods

Public Constructors

public ScrollView (Context context)

Added in API level 1

public ScrollView (Context context, AttributeSet attrs)

Added in API level 1

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

Added in API level 1

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

Public Methods

public void addView (View child, int index)

Added in API level 1

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 draw(android.graphics.Canvas), onDraw(android.graphics.Canvas), dispatchDraw(android.graphics.Canvas) or any related method.

Parameters
child the child view to add
index the position at which to add the child

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

Added in API level 1

Adds a child view with the specified layout parameters.

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

Parameters
child the child view to add
index the position at which to add the child
params the layout parameters to set on the child

public void addView (View child)

Added in API level 1

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 draw(android.graphics.Canvas), onDraw(android.graphics.Canvas), dispatchDraw(android.graphics.Canvas) or any related method.

Parameters
child the child view to add

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

Added in API level 1

Adds a child view with the specified layout parameters.

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

Parameters
child the child view to add
params the layout parameters to set on the child

public boolean arrowScroll (int direction)

Added in API level 1

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

Parameters
direction The direction corresponding to the arrow key that was pressed
Returns
  • True if we consumed the event, false otherwise

public void computeScroll ()

Added in API level 1

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.

public boolean dispatchKeyEvent (KeyEvent event)

Added in API level 1

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 The key event to be dispatched.
Returns
  • True if the event was handled, false otherwise.

public void draw (Canvas canvas)

Added in API level 1

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.

Parameters
canvas The Canvas to which the View is rendered.

public boolean executeKeyEvent (KeyEvent event)

Added in API level 1

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 The key event to execute.
Returns
  • Return true if the event was handled, else false.

public void fling (int velocityY)

Added in API level 1

Fling the scroll view

Parameters
velocityY 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.

public boolean fullScroll (int direction)

Added in API level 1

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 the scroll direction: FOCUS_UP to go the top of the view or FOCUS_DOWN to go the bottom
Returns
  • true if the key event is consumed by this method, false otherwise

public int getMaxScrollAmount ()

Added in API level 1

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

public boolean isFillViewport ()

Added in API level 1

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

Related XML Attributes
Returns
  • True if the content fills the viewport, false otherwise.

public boolean isSmoothScrollingEnabled ()

Added in API level 1

Returns
  • Whether arrow scrolling will animate its transition.

public boolean onGenericMotionEvent (MotionEvent event)

Added in API level 12

Implement this method to handle generic motion events.

Generic motion events describe joystick movements, mouse hovers, track pad touches, scroll wheel movements and other input events. 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 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 mouse hover movement...
                 return true;
             case MotionEvent.ACTION_SCROLL:
                 // process the scroll wheel movement...
                 return true;
         }
     }
     return super.onGenericMotionEvent(event);
 }

Parameters
event The generic motion event being processed.
Returns
  • True if the event was handled, false otherwise.

public void onInitializeAccessibilityEvent (AccessibilityEvent event)

Added in API level 14

Initializes an AccessibilityEvent with information about this View which is the event source. In other words, the source of an accessibility event is the view whose state change triggered firing the event.

Example: Setting the password property of an event in addition to properties set by the super implementation: 

 public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
     super.onInitializeAccessibilityEvent(event);
     event.setPassword(true);
 }

If an View.AccessibilityDelegate has been specified via calling setAccessibilityDelegate(AccessibilityDelegate) its onInitializeAccessibilityEvent(View, AccessibilityEvent) is responsible for handling this call.

Note: Always call the super implementation before adding information to the event, in case the default implementation has basic information to add.

Parameters
event The event to initialize.

public void onInitializeAccessibilityNodeInfo (AccessibilityNodeInfo info)

Added in API level 14

Initializes an AccessibilityNodeInfo with information about this view. The base implementation sets:

Subclasses should override this method, call the super implementation, and set additional attributes.

If an View.AccessibilityDelegate has been specified via calling setAccessibilityDelegate(AccessibilityDelegate) its onInitializeAccessibilityNodeInfo(View, AccessibilityNodeInfo) is responsible for handling this call.

Parameters
info The instance to initialize.

public boolean onInterceptTouchEvent (MotionEvent ev)

Added in API level 1

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 ACTION_CANCEL, and all further events will be delivered to your onTouchEvent() method and no longer appear here.

Parameters
ev The motion event being dispatched down the hierarchy.
Returns
  • 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.

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 that initiated the nested scroll
velocityX Horizontal velocity in pixels per second.
velocityY Vertical velocity in pixels per second
consumed true if the child consumed the fling, false otherwise
Returns
  • true if this parent consumed or otherwise reacted to the fling

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(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 The descendent view controlling the nested scroll
dxConsumed Horizontal scroll distance in pixels already consumed by target
dyConsumed Vertical scroll distance in pixels already consumed by target
dxUnconsumed Horizontal scroll distance in pixels not consumed by target
dyUnconsumed Vertical scroll distance in pixels not consumed by target

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 Direct child of this ViewParent containing target
target View that initiated the nested scroll
axes Flags consisting of SCROLL_AXIS_HORIZONTAL, SCROLL_AXIS_VERTICAL or both

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 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(View).

Parameters
child Direct child of this ViewParent containing target
target View that initiated the nested scroll
nestedScrollAxes Flags consisting of SCROLL_AXIS_HORIZONTAL, SCROLL_AXIS_VERTICAL or both
Returns
  • true if this ViewParent accepts the nested scroll operation

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 ACTION_UP or ACTION_CANCEL event. Implementations of this method should always call their superclass's implementation of this method if one is present.

Parameters
target View that initiated the nested scroll

public boolean onTouchEvent (MotionEvent ev)

Added in API level 1

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 The motion event.
Returns
  • True if the event was handled, false otherwise.

public boolean pageScroll (int direction)

Added in API level 1

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 the scroll direction: FOCUS_UP to go one page up or FOCUS_DOWN to go one page down
Returns
  • true if the key event is consumed by this method, false otherwise

public boolean performAccessibilityAction (int action, Bundle arguments)

Added in API level 16

Performs the specified accessibility action on the view. For possible accessibility actions look at AccessibilityNodeInfo.

If an View.AccessibilityDelegate has been specified via calling setAccessibilityDelegate(AccessibilityDelegate) its performAccessibilityAction(View, int, Bundle) is responsible for handling this call.

Parameters
action The action to perform.
arguments Optional action arguments.
Returns
  • Whether the action was performed.

public void requestChildFocus (View child, View focused)

Added in API level 1

Called when a child of this parent wants focus

Parameters
child 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 The view that is a descendant of child that actually has focus

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

Added in API level 1

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 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 The direct child making the request.
rectangle The rectangle in the child's coordinates the child wishes to be on the screen.
immediate True to forbid animated or delayed scrolling, false otherwise
Returns
  • Whether the group scrolled to handle the operation

public void requestDisallowInterceptTouchEvent (boolean disallowIntercept)

Added in API level 1

Called when a child does not want this parent and its ancestors to intercept touch events with 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 True if the child does not want the parent to intercept touch events.

public void requestLayout ()

Added in API level 1

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.

public void scrollTo (int x, int y)

Added in API level 1

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 the x position to scroll to
y the y position to scroll to

public void setFillViewport (boolean fillViewport)

Added in API level 1

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

Related XML Attributes
Parameters
fillViewport True to stretch the content's height to the viewport's boundaries, false otherwise.

public void setOverScrollMode (int mode)

Added in API level 9

Set the over-scroll mode for this view. Valid over-scroll modes are OVER_SCROLL_ALWAYS (default), OVER_SCROLL_IF_CONTENT_SCROLLS (allow over-scrolling only if the view content is larger than the container), or OVER_SCROLL_NEVER. Setting the over-scroll mode of a view will have an effect only if the view is capable of scrolling.

Parameters
mode The new over-scroll mode for this view.

public void setSmoothScrollingEnabled (boolean smoothScrollingEnabled)

Added in API level 1

Set whether arrow scrolling will animate its transition.

Parameters
smoothScrollingEnabled whether arrow scrolling will animate its transition

public boolean shouldDelayChildPressedState ()

Added in API level 14

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.

public final void smoothScrollBy (int dx, int dy)

Added in API level 1

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

Parameters
dx the number of pixels to scroll by on the X axis
dy the number of pixels to scroll by on the Y axis

public final void smoothScrollTo (int x, int y)

Added in API level 1

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

Parameters
x the position where to scroll on the X axis
y the position where to scroll on the Y axis

Protected Methods

protected int computeScrollDeltaToGetChildRectOnScreen (Rect rect)

Added in API level 1

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 The rect.
Returns
  • The scroll delta.

protected int computeVerticalScrollOffset ()

Added in API level 1

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
  • the vertical offset of the scrollbar's thumb

protected int computeVerticalScrollRange ()

Added in API level 1

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

Returns
  • the total vertical range represented by the vertical scrollbar

    The default range is the drawing height of this view.

protected float getBottomFadingEdgeStrength ()

Added in API level 1

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

protected float getTopFadingEdgeStrength ()

Added in API level 1

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

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

Added in API level 1

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 The child to measure
parentWidthMeasureSpec The width requirements for this view
parentHeightMeasureSpec The height requirements for this view

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

Added in API level 1

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 The child to measure
parentWidthMeasureSpec The width requirements for this view
widthUsed Extra space that has been used up by the parent horizontally (possibly by other children of the parent)
parentHeightMeasureSpec The height requirements for this view
heightUsed Extra space that has been used up by the parent vertically (possibly by other children of the parent)

protected void onDetachedFromWindow ()

Added in API level 1

This is called when the view is detached from a window. At this point it no longer has a surface for drawing.

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

Added in API level 1

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 This is a new size or position for this view
l Left position, relative to parent
t Top position, relative to parent
r Right position, relative to parent
b Bottom position, relative to parent

protected void onMeasure (int widthMeasureSpec, int heightMeasureSpec)

Added in API level 1

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

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

Added in API level 9

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

Parameters
scrollX New X scroll value in pixels
scrollY New Y scroll value in pixels
clampedX True if scrollX was clamped to an over-scroll boundary
clampedY True if scrollY was clamped to an over-scroll boundary

protected boolean onRequestFocusInDescendants (int direction, Rect previouslyFocusedRect)

Added in API level 1

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 One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and FOCUS_RIGHT
previouslyFocusedRect 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
  • Whether focus was taken.

protected void onRestoreInstanceState (Parcelable state)

Added in API level 1

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.

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

protected Parcelable onSaveInstanceState ()

Added in API level 1

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.

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

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

Added in API level 1

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 Current width of this view.
h Current height of this view.
oldw Old width of this view.
oldh Old height of this view.