public
static
class
View.DragShadowBuilder
extends Object
| java.lang.Object | |
| ↳ | android.view.View.DragShadowBuilder |
Creates an image that the system displays during the drag and drop
operation. This is called a "drag shadow". The default implementation
for a DragShadowBuilder based on a View returns an image that has exactly the same
appearance as the given View. The default also positions the center of the drag shadow
directly under the touch point. If no View is provided (the constructor with no parameters
is used), and onProvideShadowMetrics() and
onDrawShadow() are not overridden, then the
default is an invisible drag shadow.
You are not required to use the View you provide to the constructor as the basis of the
drag shadow. The onDrawShadow() method allows you to draw
anything you want as the drag shadow.
You pass a DragShadowBuilder object to the system when you start the drag. The system
calls onProvideShadowMetrics() to get the
size and position of the drag shadow. It uses this data to construct a
Canvas object, then it calls onDrawShadow()
so that your application can draw the shadow image in the Canvas.
For a guide to implementing drag and drop features, read the Drag and Drop developer guide.
Public constructors | |
|---|---|
View.DragShadowBuilder(View view)
Constructs a shadow image builder based on a View. |
|
View.DragShadowBuilder()
Construct a shadow builder object with no associated View. |
|
Public methods | |
|---|---|
final
View
|
getView()
Returns the View object that had been passed to the
|
void
|
onDrawShadow(Canvas canvas)
Draws the shadow image. |
void
|
onProvideShadowMetrics(Point outShadowSize, Point outShadowTouchPoint)
Provides the metrics for the shadow image. |
Inherited methods | |
|---|---|
 From
class
java.lang.Object
| |
View.DragShadowBuilder (View view)
Constructs a shadow image builder based on a View. By default, the resulting drag shadow will have the same appearance and dimensions as the View, with the touch point over the center of the View.
| Parameters | |
|---|---|
view |
View:
A View. Any View in scope can be used.
|
View.DragShadowBuilder ()
Construct a shadow builder object with no associated View. This
constructor variant is only useful when the onProvideShadowMetrics(Point, Point)
and onDrawShadow(Canvas) methods are also overridden in order
to supply the drag shadow's dimensions and appearance without
reference to any View object. If they are not overridden, then the result is an
invisible drag shadow.
View getView ()
Returns the View object that had been passed to the
View.DragShadowBuilder(View)
constructor. If that View parameter was null or if the
View.DragShadowBuilder()
constructor was used to instantiate the builder object, this method will return
null.
| Returns | |
|---|---|
View |
The View object associate with this builder object. |
void onDrawShadow (Canvas canvas)
Draws the shadow image. The system creates the Canvas object
based on the dimensions it received from the
onProvideShadowMetrics(Point, Point) callback.
| Parameters | |
|---|---|
canvas |
Canvas:
A Canvas object in which to draw the shadow image.
|
void onProvideShadowMetrics (Point outShadowSize, Point outShadowTouchPoint)
Provides the metrics for the shadow image. These include the dimensions of the shadow image, and the point within that shadow that should be centered under the touch location while dragging.
The default implementation sets the dimensions of the shadow to be the same as the dimensions of the View itself and centers the shadow under the touch point.
| Parameters | |
|---|---|
outShadowSize |
Point:
A Point containing the width and height
of the shadow image. Your application must set x to the
desired width and must set y to the desired height of the
image. |
outShadowTouchPoint |
Point:
A Point for the position within the
shadow image that should be underneath the touch point during the drag and drop
operation. Your application must set x to the
X coordinate and y to the Y coordinate of this position.
|
Developers