Added in API level 9

OverScroller


public class OverScroller
extends Object

java.lang.Object
   ↳ android.widget.OverScroller


This class encapsulates scrolling with the ability to overshoot the bounds of a scrolling operation. This class is a drop-in replacement for Scroller in most cases.

Summary

Public constructors

OverScroller(Context context)

Creates an OverScroller with a viscous fluid scroll interpolator and flywheel.

OverScroller(Context context, Interpolator interpolator)

Creates an OverScroller with flywheel enabled.

OverScroller(Context context, Interpolator interpolator, float bounceCoefficientX, float bounceCoefficientY)

This constructor is deprecated. Use OverScroller(android.content.Context, android.view.animation.Interpolator) instead.

OverScroller(Context context, Interpolator interpolator, float bounceCoefficientX, float bounceCoefficientY, boolean flywheel)

This constructor is deprecated. Use OverScroller(android.content.Context, android.view.animation.Interpolator) instead.

Public methods

void abortAnimation()

Stops the animation.

boolean computeScrollOffset()

Call this when you want to know the new location.

void fling(int startX, int startY, int velocityX, int velocityY, int minX, int maxX, int minY, int maxY)
void fling(int startX, int startY, int velocityX, int velocityY, int minX, int maxX, int minY, int maxY, int overX, int overY)

Start scrolling based on a fling gesture.

final void forceFinished(boolean finished)

Force the finished field to a particular value.

float getCurrVelocity()

Returns the absolute value of the current velocity.

final int getCurrX()

Returns the current X offset in the scroll.

final int getCurrY()

Returns the current Y offset in the scroll.

final int getFinalX()

Returns where the scroll will end.

final int getFinalY()

Returns where the scroll will end.

final int getStartX()

Returns the start X offset in the scroll.

final int getStartY()

Returns the start Y offset in the scroll.

final boolean isFinished()

Returns whether the scroller has finished scrolling.

boolean isOverScrolled()

Returns whether the current Scroller is currently returning to a valid position.

void notifyHorizontalEdgeReached(int startX, int finalX, int overX)

Notify the scroller that we've reached a horizontal boundary.

void notifyVerticalEdgeReached(int startY, int finalY, int overY)

Notify the scroller that we've reached a vertical boundary.

final void setFriction(float friction)

The amount of friction applied to flings.

boolean springBack(int startX, int startY, int minX, int maxX, int minY, int maxY)

Call this when you want to 'spring back' into a valid coordinate range.

void startScroll(int startX, int startY, int dx, int dy, int duration)

Start scrolling by providing a starting point and the distance to travel.

void startScroll(int startX, int startY, int dx, int dy)

Start scrolling by providing a starting point and the distance to travel.

Inherited methods

Public constructors

OverScroller

Added in API level 9
public OverScroller (Context context)

Creates an OverScroller with a viscous fluid scroll interpolator and flywheel.

OverScroller

Added in API level 9
public OverScroller (Context context, 
                Interpolator interpolator)

Creates an OverScroller with flywheel enabled.

Parameters
context Context: The context of this application.

interpolator Interpolator: The scroll interpolator. If null, a default (viscous) interpolator will be used.

OverScroller

Added in API level 9
public OverScroller (Context context, 
                Interpolator interpolator, 
                float bounceCoefficientX, 
                float bounceCoefficientY)

This constructor is deprecated.
Use OverScroller(android.content.Context, android.view.animation.Interpolator) instead.

Creates an OverScroller with flywheel enabled.

Parameters
context Context: The context of this application.

interpolator Interpolator: The scroll interpolator. If null, a default (viscous) interpolator will be used.

bounceCoefficientX float: A value between 0 and 1 that will determine the proportion of the velocity which is preserved in the bounce when the horizontal edge is reached. A null value means no bounce. This behavior is no longer supported and this coefficient has no effect.

bounceCoefficientY float: Same as bounceCoefficientX but for the vertical direction. This behavior is no longer supported and this coefficient has no effect.

OverScroller

Added in API level 11
public OverScroller (Context context, 
                Interpolator interpolator, 
                float bounceCoefficientX, 
                float bounceCoefficientY, 
                boolean flywheel)

This constructor is deprecated.
Use OverScroller(android.content.Context, android.view.animation.Interpolator) instead.

Creates an OverScroller.

Parameters
context Context: The context of this application.

interpolator Interpolator: The scroll interpolator. If null, a default (viscous) interpolator will be used.

bounceCoefficientX float: A value between 0 and 1 that will determine the proportion of the velocity which is preserved in the bounce when the horizontal edge is reached. A null value means no bounce. This behavior is no longer supported and this coefficient has no effect.

bounceCoefficientY float: Same as bounceCoefficientX but for the vertical direction. This behavior is no longer supported and this coefficient has no effect.

flywheel boolean: If true, successive fling motions will keep on increasing scroll speed.

Public methods

abortAnimation

Added in API level 9
public void abortAnimation ()

Stops the animation. Contrary to forceFinished(boolean), aborting the animating causes the scroller to move to the final x and y positions.

computeScrollOffset

Added in API level 9
public boolean computeScrollOffset ()

Call this when you want to know the new location. If it returns true, the animation is not yet finished.

Returns
boolean

fling

Added in API level 9
public void fling (int startX, 
                int startY, 
                int velocityX, 
                int velocityY, 
                int minX, 
                int maxX, 
                int minY, 
                int maxY)

Parameters
startX int

startY int

velocityX int

velocityY int

minX int

maxX int

minY int

maxY int

fling

Added in API level 9
public void fling (int startX, 
                int startY, 
                int velocityX, 
                int velocityY, 
                int minX, 
                int maxX, 
                int minY, 
                int maxY, 
                int overX, 
                int overY)

Start scrolling based on a fling gesture. The distance traveled will depend on the initial velocity of the fling.

Parameters
startX int: Starting point of the scroll (X)

startY int: Starting point of the scroll (Y)

velocityX int: Initial velocity of the fling (X) measured in pixels per second.

velocityY int: Initial velocity of the fling (Y) measured in pixels per second

minX int: Minimum X value. The scroller will not scroll past this point unless overX > 0. If overfling is allowed, it will use minX as a springback boundary.

maxX int: Maximum X value. The scroller will not scroll past this point unless overX > 0. If overfling is allowed, it will use maxX as a springback boundary.

minY int: Minimum Y value. The scroller will not scroll past this point unless overY > 0. If overfling is allowed, it will use minY as a springback boundary.

maxY int: Maximum Y value. The scroller will not scroll past this point unless overY > 0. If overfling is allowed, it will use maxY as a springback boundary.

overX int: Overfling range. If > 0, horizontal overfling in either direction will be possible.

overY int: Overfling range. If > 0, vertical overfling in either direction will be possible.

forceFinished

Added in API level 9
public final void forceFinished (boolean finished)

Force the finished field to a particular value. Contrary to abortAnimation(), forcing the animation to finished does NOT cause the scroller to move to the final x and y position.

Parameters
finished boolean: The new finished value.

getCurrVelocity

Added in API level 14
public float getCurrVelocity ()

Returns the absolute value of the current velocity.

Returns
float The original velocity less the deceleration, norm of the X and Y velocity vector.

getCurrX

Added in API level 9
public final int getCurrX ()

Returns the current X offset in the scroll.

Returns
int The new X offset as an absolute distance from the origin.

getCurrY

Added in API level 9
public final int getCurrY ()

Returns the current Y offset in the scroll.

Returns
int The new Y offset as an absolute distance from the origin.

getFinalX

Added in API level 9
public final int getFinalX ()

Returns where the scroll will end. Valid only for "fling" scrolls.

Returns
int The final X offset as an absolute distance from the origin.

getFinalY

Added in API level 9
public final int getFinalY ()

Returns where the scroll will end. Valid only for "fling" scrolls.

Returns
int The final Y offset as an absolute distance from the origin.

getStartX

Added in API level 9
public final int getStartX ()

Returns the start X offset in the scroll.

Returns
int The start X offset as an absolute distance from the origin.

getStartY

Added in API level 9
public final int getStartY ()

Returns the start Y offset in the scroll.

Returns
int The start Y offset as an absolute distance from the origin.

isFinished

Added in API level 9
public final boolean isFinished ()

Returns whether the scroller has finished scrolling.

Returns
boolean True if the scroller has finished scrolling, false otherwise.

isOverScrolled

Added in API level 9
public boolean isOverScrolled ()

Returns whether the current Scroller is currently returning to a valid position. Valid bounds were provided by the fling(int, int, int, int, int, int, int, int, int, int) method. One should check this value before calling startScroll(int, int, int, int) as the interpolation currently in progress to restore a valid position will then be stopped. The caller has to take into account the fact that the started scroll will start from an overscrolled position.

Returns
boolean true when the current position is overscrolled and in the process of interpolating back to a valid value.

notifyHorizontalEdgeReached

Added in API level 9
public void notifyHorizontalEdgeReached (int startX, 
                int finalX, 
                int overX)

Notify the scroller that we've reached a horizontal boundary. Normally the information to handle this will already be known when the animation is started, such as in a call to one of the fling functions. However there are cases where this cannot be known in advance. This function will transition the current motion and animate from startX to finalX as appropriate.

Parameters
startX int: Starting/current X position

finalX int: Desired final X position

overX int: Magnitude of overscroll allowed. This should be the maximum desired distance from finalX. Absolute value - must be positive.

notifyVerticalEdgeReached

Added in API level 9
public void notifyVerticalEdgeReached (int startY, 
                int finalY, 
                int overY)

Notify the scroller that we've reached a vertical boundary. Normally the information to handle this will already be known when the animation is started, such as in a call to one of the fling functions. However there are cases where this cannot be known in advance. This function will animate a parabolic motion from startY to finalY.

Parameters
startY int: Starting/current Y position

finalY int: Desired final Y position

overY int: Magnitude of overscroll allowed. This should be the maximum desired distance from finalY. Absolute value - must be positive.

setFriction

Added in API level 11
public final void setFriction (float friction)

The amount of friction applied to flings. The default value is ViewConfiguration#getScrollFriction.

Parameters
friction float: A scalar dimension-less value representing the coefficient of friction.

springBack

Added in API level 9
public boolean springBack (int startX, 
                int startY, 
                int minX, 
                int maxX, 
                int minY, 
                int maxY)

Call this when you want to 'spring back' into a valid coordinate range.

Parameters
startX int: Starting X coordinate

startY int: Starting Y coordinate

minX int: Minimum valid X value

maxX int: Maximum valid X value

minY int: Minimum valid Y value

maxY int: Minimum valid Y value

Returns
boolean true if a springback was initiated, false if startX and startY were already within the valid range.

startScroll

Added in API level 9
public void startScroll (int startX, 
                int startY, 
                int dx, 
                int dy, 
                int duration)

Start scrolling by providing a starting point and the distance to travel.

Parameters
startX int: Starting horizontal scroll offset in pixels. Positive numbers will scroll the content to the left.

startY int: Starting vertical scroll offset in pixels. Positive numbers will scroll the content up.

dx int: Horizontal distance to travel. Positive numbers will scroll the content to the left.

dy int: Vertical distance to travel. Positive numbers will scroll the content up.

duration int: Duration of the scroll in milliseconds.

startScroll

Added in API level 9
public void startScroll (int startX, 
                int startY, 
                int dx, 
                int dy)

Start scrolling by providing a starting point and the distance to travel. The scroll will use the default value of 250 milliseconds for the duration.

Parameters
startX int: Starting horizontal scroll offset in pixels. Positive numbers will scroll the content to the left.

startY int: Starting vertical scroll offset in pixels. Positive numbers will scroll the content up.

dx int: Horizontal distance to travel. Positive numbers will scroll the content to the left.

dy int: Vertical distance to travel. Positive numbers will scroll the content up.