net.simonvt.menudrawer
Class Scroller

java.lang.Object
  net.simonvt.menudrawer.Scroller

public class Scroller
extends Object

This class encapsulates scrolling. The duration of the scroll can be passed in the constructor and specifies the maximum time that the scrolling animation should take. Past this time, the scrolling is automatically moved to its final stage and computeScrollOffset() will always return false to indicate that scrolling is over.

Constructor Summary

Scroller(android.content.Context context)
Create a Scroller with the default duration and interpolator.

Scroller(android.content.Context context, android.view.animation.Interpolator interpolator)
Create a Scroller with the specified interpolator.

Scroller(android.content.Context context, android.view.animation.Interpolator interpolator, boolean flywheel)
Create a Scroller with the specified interpolator.

Method Summary

void	abortAnimation() Stops the animation.
boolean	computeScrollOffset() Call this when you want to know the new location.
void	extendDuration(int extend) Extend the scroll animation.
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	forceFinished(boolean finished) Force the finished field to a particular value.
float	getCurrVelocity() Returns the current velocity.
int	getCurrX() Returns the current X offset in the scroll.
int	getCurrY() Returns the current Y offset in the scroll.
int	getDuration() Returns how long the scroll event will take, in milliseconds.
int	getFinalX() Returns where the scroll will end.
int	getFinalY() Returns where the scroll will end.
int	getStartX() Returns the start X offset in the scroll.
int	getStartY() Returns the start Y offset in the scroll.
boolean	isFinished() Returns whether the scroller has finished scrolling.
boolean	isScrollingInDirection(float xvel, float yvel)
void	setFinalX(int newX) Sets the final position (X) for this scroller.
void	setFinalY(int newY) Sets the final position (Y) for this scroller.
void	setFriction(float friction) The amount of friction applied to flings.
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.
int	timePassed() Returns the time elapsed since the beginning of the scrolling.

Methods inherited from class java.lang.Object

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

Constructor Detail

Scroller

public Scroller(android.content.Context context)

Create a Scroller with the default duration and interpolator.

Scroller

public Scroller(android.content.Context context,
                android.view.animation.Interpolator interpolator)

Create a Scroller with the specified interpolator. If the interpolator is null, the default (viscous) interpolator will be used. "Flywheel" behavior will be in effect for apps targeting Honeycomb or newer.

Scroller

public Scroller(android.content.Context context,
                android.view.animation.Interpolator interpolator,
                boolean flywheel)

Create a Scroller with the specified interpolator. If the interpolator is null, the default (viscous) interpolator will be used. Specify whether or not to support progressive "flywheel" behavior in flinging.

Method Detail

setFriction

public final void setFriction(float friction)

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

Parameters:

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

isFinished

public final boolean isFinished()

Returns whether the scroller has finished scrolling.

Returns:

True if the scroller has finished scrolling, false otherwise.

forceFinished

public final void forceFinished(boolean finished)

Force the finished field to a particular value.

Parameters:

finished - The new finished value.

getDuration

public final int getDuration()

Returns how long the scroll event will take, in milliseconds.

Returns:

The duration of the scroll in milliseconds.

getCurrX

public final int getCurrX()

Returns the current X offset in the scroll.

Returns:

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

getCurrY

public final int getCurrY()

Returns the current Y offset in the scroll.

Returns:

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

getCurrVelocity

public float getCurrVelocity()

Returns the current velocity.

Returns:

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

getStartX

public final int getStartX()

Returns the start X offset in the scroll.

Returns:

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

getStartY

public final int getStartY()

Returns the start Y offset in the scroll.

Returns:

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

getFinalX

public final int getFinalX()

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

Returns:

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

getFinalY

public final int getFinalY()

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

Returns:

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

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.

abortAnimation

public void abortAnimation()

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

See Also:

forceFinished(boolean)

extendDuration

public void extendDuration(int extend)

Extend the scroll animation. This allows a running animation to scroll further and longer, when used with setFinalX(int) or setFinalY(int).

Parameters:

extend - Additional time to scroll in milliseconds.

See Also:

setFinalX(int), setFinalY(int)

timePassed

public int timePassed()

Returns the time elapsed since the beginning of the scrolling.

Returns:

The elapsed time in milliseconds.

setFinalX

public void setFinalX(int newX)

Sets the final position (X) for this scroller.

Parameters:

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

See Also:

extendDuration(int), setFinalY(int)

setFinalY

public void setFinalY(int newY)

Sets the final position (Y) for this scroller.

Parameters:

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

See Also:

extendDuration(int), setFinalX(int)

isScrollingInDirection

public boolean isScrollingInDirection(float xvel,
                                      float yvel)