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Android APIs
public class

EdgeEffectCompat

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

Class Overview

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.

Summary

Public Constructors
EdgeEffectCompat ( Context context)
Construct a new EdgeEffect themed using the given context.
Public Methods
boolean draw ( 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.
[Expand]
Inherited Methods
From class java.lang.Object

Public Constructors

public EdgeEffectCompat ( 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

Public Methods

public boolean draw ( 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

public void finish ()

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

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.

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.

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 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.

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 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.

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