Android APIs
public class

ScrollerCompat

extends Object
java.lang.Object
   ↳ android.support.v4.widget.ScrollerCompat

Class Overview

Provides access to new Scroller APIs when available.

This class provides a platform version-independent mechanism for obeying the current device's preferred scroll physics and fling behavior. It offers a subset of the APIs from Scroller or OverScroller.

Summary

Public Methods
void abortAnimation()
Stops the animation.
boolean computeScrollOffset()
Call this when you want to know the new location.
static ScrollerCompat create(Context context)
static ScrollerCompat create(Context context, Interpolator interpolator)
void fling(int startX, int startY, int velocityX, int velocityY, int minX, int maxX, int minY, int maxY)
Start scrolling based on a fling gesture.
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.
float getCurrVelocity()
Returns the current velocity on platform versions that support it.
int getCurrX()
Returns the current X offset in the scroll.
int getCurrY()
Returns the current Y offset in the scroll.
int getFinalX()
int getFinalY()
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.
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)
Start scrolling by providing a starting point and the distance to travel.
void startScroll(int startX, int startY, int dx, int dy, int duration)
Start scrolling by providing a starting point and the distance to travel.
[Expand]
Inherited Methods
From class java.lang.Object

Public Methods

public void abortAnimation ()

Stops the animation. Aborting the animation causes the scroller to move to the final x and y position.

public boolean computeScrollOffset ()

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

public static ScrollerCompat create (Context context)

public static ScrollerCompat create (Context context, Interpolator interpolator)

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

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

Parameters
startX Starting point of the scroll (X)
startY Starting point of the scroll (Y)
velocityX Initial velocity of the fling (X) measured in pixels per second.
velocityY Initial velocity of the fling (Y) measured in pixels per second
minX Minimum X value. The scroller will not scroll past this point.
maxX Maximum X value. The scroller will not scroll past this point.
minY Minimum Y value. The scroller will not scroll past this point.
maxY Maximum Y value. The scroller will not scroll past this point.

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 travelled will depend on the initial velocity of the fling.

Parameters
startX Starting point of the scroll (X)
startY Starting point of the scroll (Y)
velocityX Initial velocity of the fling (X) measured in pixels per second.
velocityY Initial velocity of the fling (Y) measured in pixels per second
minX Minimum X value. The scroller will not scroll past this point.
maxX Maximum X value. The scroller will not scroll past this point.
minY Minimum Y value. The scroller will not scroll past this point.
maxY Maximum Y value. The scroller will not scroll past this point.
overX Overfling range. If > 0, horizontal overfling in either direction will be possible.
overY Overfling range. If > 0, vertical overfling in either direction will be possible.

public float getCurrVelocity ()

Returns the current velocity on platform versions that support it.

The device must support at least API level 14 (Ice Cream Sandwich). On older platform versions this method will return 0. This method should only be used as input for nonessential visual effects such as EdgeEffectCompat.

Returns
  • The original velocity less the deceleration. Result may be negative.

public int getCurrX ()

Returns the current X offset in the scroll.

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

public int getCurrY ()

Returns the current Y offset in the scroll.

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

public int getFinalX ()

Returns
  • The final X position for the scroll in progress, if known.

public int getFinalY ()

Returns
  • The final Y position for the scroll in progress, if known.

public boolean isFinished ()

Returns whether the scroller has finished scrolling.

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

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

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 Starting/current X position
finalX Desired final X position
overX Magnitude of overscroll allowed. This should be the maximum desired distance from finalX. Absolute value - must be positive.

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 Starting/current Y position
finalY Desired final Y position
overY Magnitude of overscroll allowed. This should be the maximum desired distance from finalY. Absolute value - must be positive.

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 Starting X coordinate
startY Starting Y coordinate
minX Minimum valid X value
maxX Maximum valid X value
minY Minimum valid Y value
maxY Maximum valid Y value
Returns
  • true if a springback was initiated, false if startX and startY were already within the valid range.

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 Starting horizontal scroll offset in pixels. Positive numbers will scroll the content to the left.
startY Starting vertical scroll offset in pixels. Positive numbers will scroll the content up.
dx Horizontal distance to travel. Positive numbers will scroll the content to the left.
dy Vertical distance to travel. Positive numbers will scroll the content up.

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 Starting horizontal scroll offset in pixels. Positive numbers will scroll the content to the left.
startY Starting vertical scroll offset in pixels. Positive numbers will scroll the content up.
dx Horizontal distance to travel. Positive numbers will scroll the content to the left.
dy Vertical distance to travel. Positive numbers will scroll the content up.
duration Duration of the scroll in milliseconds.