public
class
EdgeEffect
extends Object
| java.lang.Object | |
| ↳ | android.widget.EdgeEffect |
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
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.
Public constructors | |
|---|---|
EdgeEffect(Context context)
Construct a new EdgeEffect with a theme appropriate for the provided context. |
|
Public methods | |
|---|---|
boolean
|
draw(Canvas canvas)
Draw into the provided canvas. |
void
|
finish()
Immediately finish the current animation. |
int
|
getColor()
Return the color of this edge effect in argb. |
int
|
getMaxHeight()
Return the maximum height that the edge effect will be drawn at given the original
|
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
|
onPull(float deltaDistance, float displacement)
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
|
setColor(int color)
Set the color of this edge effect in argb. |
void
|
setSize(int width, int height)
Set the size of this edge effect in pixels. |
Inherited methods | |
|---|---|
 From
class
java.lang.Object
| |
EdgeEffect (Context context)
Construct a new EdgeEffect with a theme appropriate for the provided context.
| Parameters | |
|---|---|
context |
Context:
Context used to provide theming and resource information for the EdgeEffect
|
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 |
void finish ()
Immediately finish the current animation.
After this call isFinished() will return true.
int getColor ()
Return the color of this edge effect in argb.
| Returns | |
|---|---|
int |
The color of this edge effect in argb |
int getMaxHeight ()
Return the maximum height that the edge effect will be drawn at given the original
input size.
| Returns | |
|---|---|
int |
The maximum height of the edge effect |
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 | |
|---|---|
boolean |
true if animation is finished, false if drawing should continue on the next frame. |
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 |
int:
Velocity at impact in pixels per second.
|
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 invalidate() after this
and draw the results accordingly.
Views using EdgeEffect should favor onPull(float, float) when the displacement
of the pull point is known.
| 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.
|
Developers
void 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() after this
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.
|
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 invalidate() and thereby
draw the results accordingly.
void setColor (int color)
Set the color of this edge effect in argb.
| Parameters | |
|---|---|
color |
int:
Color in argb
|
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
|