android.support.v4.widget
Class ScrollerCompat

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

public class ScrollerCompat
extends Object

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.

Method Summary

void	abortAnimation() Stops the animation.
boolean	computeScrollOffset() Call this when you want to know the new location.
static ScrollerCompat	create(android.content.Context context)
static ScrollerCompat	create(android.content.Context context, android.view.animation.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.
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.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

create

public static ScrollerCompat create(android.content.Context context)

create

public static ScrollerCompat create(android.content.Context context,
                                    android.view.animation.Interpolator interpolator)

isFinished

public boolean isFinished()

Returns whether the scroller has finished scrolling.

Returns:

True if the scroller has finished scrolling, false otherwise.

getCurrX

public int getCurrX()

Returns the current X offset in the scroll.

Returns:

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

getCurrY

public int getCurrY()

Returns the current Y offset in the scroll.

Returns:

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

getFinalX

public int getFinalX()

Returns:

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

getFinalY

public int getFinalY()

Returns:

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

getCurrVelocity

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.

computeScrollOffset

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.

startScroll

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.

startScroll

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.

fling

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.

fling

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.

abortAnimation

public void abortAnimation()

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

notifyHorizontalEdgeReached

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.

notifyVerticalEdgeReached

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.

isOverScrolled

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.