android.support.v4.widget
Class EdgeEffectCompat

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

public class EdgeEffectCompat
extends Object

Helper for accessing EdgeEffect introduced after API level 4 in a backwards compatible fashion. This class is used to access EdgeEffect on platform versions that support it. When running on older platforms it will result in no-ops. It should be used by views that wish to use the standard Android visual effects at the edges of scrolling containers.

Constructor Summary

EdgeEffectCompat(android.content.Context context)
Construct a new EdgeEffect themed using the given context.

Method Summary

boolean	draw(android.graphics.Canvas canvas) Draw into the provided canvas.
void	finish() Immediately finish the current animation.
boolean	isFinished() Reports if this EdgeEffectCompat's animation is finished.
boolean	onAbsorb(int velocity) Call when the effect absorbs an impact at the given velocity.
boolean	onPull(float deltaDistance) A view should call this when content is pulled away from an edge by the user.
boolean	onRelease() Call when the object is released after being pulled.
void	setSize(int width, int height) Set the size of this edge effect in pixels.

Methods inherited from class java.lang.Object

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

Constructor Detail

EdgeEffectCompat

public EdgeEffectCompat(android.content.Context context)

Construct a new EdgeEffect themed using the given context.

Note: On platform versions that do not support EdgeEffect, all operations on the newly constructed object will be mocked/no-ops.

Parameters:

context - Context to use for theming the effect

Method Detail

setSize

public void setSize(int width,
                    int height)

Set the size of this edge effect in pixels.

Parameters:

width - Effect width in pixels

height - Effect height in pixels

isFinished

public boolean isFinished()

Reports if this EdgeEffectCompat's animation is finished. If this method returns false after a call to draw(Canvas) the host widget should schedule another drawing pass to continue the animation.

Returns:

true if animation is finished, false if drawing should continue on the next frame.

finish

public void finish()

Immediately finish the current animation. After this call isFinished() will return true.

onPull

public boolean onPull(float deltaDistance)

A view should call this when content is pulled away from an edge by the user. This will update the state of the current visual effect and its associated animation. The host view should always View.invalidate() if this method returns true and draw the results accordingly.

Parameters:

deltaDistance - Change in distance since the last call. Values may be 0 (no change) to 1.f (full length of the view) or negative values to express change back toward the edge reached to initiate the effect.

Returns:

true if the host view should call invalidate, false if it should not.

onRelease

public boolean onRelease()

Call when the object is released after being pulled. This will begin the "decay" phase of the effect. After calling this method the host view should View.invalidate() if this method returns true and thereby draw the results accordingly.

Returns:

true if the host view should invalidate, false if it should not.

onAbsorb

public boolean onAbsorb(int velocity)

Call when the effect absorbs an impact at the given velocity. Used when a fling reaches the scroll boundary.

When using a Scroller or OverScroller, the method getCurrVelocity will provide a reasonable approximation to use here.

Parameters:

velocity - Velocity at impact in pixels per second.

Returns:

true if the host view should invalidate, false if it should not.

draw

public boolean draw(android.graphics.Canvas canvas)

Draw into the provided canvas. Assumes that the canvas has been rotated accordingly and the size has been set. The effect will be drawn the full width of X=0 to X=width, beginning from Y=0 and extending to some factor < 1.f of height.

Parameters:

canvas - Canvas to draw into

Returns:

true if drawing should continue beyond this frame to continue the animation