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EdgeEffectCompat

public final class EdgeEffectCompat
extends Object

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


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, float displacement)

A view should call this when content is pulled away from an edge by the user.

boolean onPull(float deltaDistance)

This method is deprecated. use onPull(float, float)

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.

Inherited methods

From class java.lang.Object

Public constructors

EdgeEffectCompat

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: Context to use for theming the effect

Public methods

draw

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: Canvas to draw into
Returns
boolean true if drawing should continue beyond this frame to continue the animation

finish

void finish ()

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

isFinished

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

onAbsorb

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 int: Velocity at impact in pixels per second.
Returns
boolean true if the host view should invalidate, false if it should not.

onPull

boolean onPull (float deltaDistance, 
                float displacement)

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 float: 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.
displacement float: The displacement from the starting side of the effect of the point initiating the pull. In the case of touch this is the finger position. Values may be from 0-1.
Returns
boolean true if the host view should call invalidate, false if it should not.

onPull

boolean onPull (float deltaDistance)

This method is deprecated.
use onPull(float, float)

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

onRelease

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

setSize

void setSize (int width, 
                int height)

Set the size of this edge effect in pixels.

Parameters
width int: Effect width in pixels
height int: Effect height in pixels
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