it.sephiroth.android.library.widget

Class EdgeEffect

java.lang.Object

it.sephiroth.android.library.widget.EdgeEffect

public class EdgeEffect
extends java.lang.Object

This class performs the graphical effect used at the edges of scrollable widgets when the user scrolls beyond the content bounds in 2D space.

EdgeEffect is stateful. Custom widgets using EdgeEffect should create an instance for each edge that should show the effect, feed it input data using the methods onAbsorb(int), onPull(float), and onRelease(), and draw the effect using draw(Canvas) in the widget's overridden View.draw(Canvas) method. If isFinished() returns false after drawing, the edge effect's animation is not yet complete and the widget should schedule another drawing pass to continue the animation.

When drawing, widgets should draw their main content and child views first, usually by invoking super.draw(canvas) from an overridden draw method. (This will invoke onDraw and dispatch drawing to child views as needed.) The edge effect may then be drawn on top of the view's content using the draw(Canvas) method.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DIRECTION_HORIZONTAL
static int	DIRECTION_VERTICAL

Constructor Summary

Constructors

Constructor and Description
EdgeEffect(android.content.Context context, int direction) Construct a new EdgeEffect with a theme appropriate for the provided context.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	draw(android.graphics.Canvas canvas) Draw into the provided canvas.
void	finish() Immediately finish the current animation.
android.graphics.Rect	getBounds(boolean reverse) Returns the bounds of the edge effect.
boolean	isFinished() Reports if this EdgeEffect's animation is finished.
void	onAbsorb(int velocity) Call when the effect absorbs an impact at the given velocity.
void	onPull(float deltaDistance) A view should call this when content is pulled away from an edge by the user.
void	onRelease() Call when the object is released after being pulled.
void	setPosition(int x, int y) Set the position of this edge effect in pixels.
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

Field Detail

DIRECTION_VERTICAL

public static final int DIRECTION_VERTICAL

See Also:

Constant Field Values

DIRECTION_HORIZONTAL

public static final int DIRECTION_HORIZONTAL

See Also:

Constant Field Values

Constructor Detail

EdgeEffect

public EdgeEffect(android.content.Context context,
          int direction)

Construct a new EdgeEffect with a theme appropriate for the provided context.

Parameters:

context - Context used to provide theming and resource information for the EdgeEffect

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

setPosition

public void setPosition(int x,
               int y)

Set the position of this edge effect in pixels. This position is only used by getBounds(boolean).

Parameters:

x - The position of the edge effect on the X axis

y - The position of the edge effect on the Y axis

isFinished

public boolean isFinished()

Reports if this EdgeEffect'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 void 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() after this 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.

onRelease

public void 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() and thereby draw the results accordingly.

onAbsorb

public void 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.

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

getBounds

public android.graphics.Rect getBounds(boolean reverse)

Returns the bounds of the edge effect.