public
class
ScaleGestureDetector
extends Object
| java.lang.Object | |
| ↳ | android.view.ScaleGestureDetector |
Detects scaling transformation gestures using the supplied MotionEvents.
The ScaleGestureDetector.OnScaleGestureListener callback will notify users when a particular
gesture event has occurred.
This class should only be used with MotionEvents reported via touch.
To use this class:
Developers
ScaleGestureDetector for your
View
onTouchEvent(MotionEvent) method ensure you call
onTouchEvent(MotionEvent). The methods defined in your
callback will be executed when the events occur.
Nested classes | |
|---|---|
interface |
ScaleGestureDetector.OnScaleGestureListener
The listener for receiving notifications when gestures occur. |
class |
ScaleGestureDetector.SimpleOnScaleGestureListener
A convenience class to extend when you only want to listen for a subset of scaling-related events. |
Public constructors | |
|---|---|
ScaleGestureDetector(Context context, ScaleGestureDetector.OnScaleGestureListener listener)
Creates a ScaleGestureDetector with the supplied listener. |
|
ScaleGestureDetector(Context context, ScaleGestureDetector.OnScaleGestureListener listener, Handler handler)
Creates a ScaleGestureDetector with the supplied listener. |
|
Public methods | |
|---|---|
float
|
getCurrentSpan()
Return the average distance between each of the pointers forming the gesture in progress through the focal point. |
float
|
getCurrentSpanX()
Return the average X distance between each of the pointers forming the gesture in progress through the focal point. |
float
|
getCurrentSpanY()
Return the average Y distance between each of the pointers forming the gesture in progress through the focal point. |
long
|
getEventTime()
Return the event time of the current event being processed. |
float
|
getFocusX()
Get the X coordinate of the current gesture's focal point. |
float
|
getFocusY()
Get the Y coordinate of the current gesture's focal point. |
float
|
getPreviousSpan()
Return the previous average distance between each of the pointers forming the gesture in progress through the focal point. |
float
|
getPreviousSpanX()
Return the previous average X distance between each of the pointers forming the gesture in progress through the focal point. |
float
|
getPreviousSpanY()
Return the previous average Y distance between each of the pointers forming the gesture in progress through the focal point. |
float
|
getScaleFactor()
Return the scaling factor from the previous scale event to the current event. |
long
|
getTimeDelta()
Return the time difference in milliseconds between the previous accepted scaling event and the current scaling event. |
boolean
|
isInProgress()
Returns |
boolean
|
isQuickScaleEnabled()
Return whether the quick scale gesture, in which the user performs a double tap followed by a swipe, should perform scaling. |
boolean
|
isStylusScaleEnabled()
Return whether the stylus scale gesture, in which the user uses a stylus and presses the button, should perform scaling. |
boolean
|
onTouchEvent(MotionEvent event)
Accepts MotionEvents and dispatches events to a |
void
|
setQuickScaleEnabled(boolean scales)
Set whether the associated |
void
|
setStylusScaleEnabled(boolean scales)
Sets whether the associates |
Inherited methods | |
|---|---|
 From
class
java.lang.Object
| |
ScaleGestureDetector (Context context, ScaleGestureDetector.OnScaleGestureListener listener)
Creates a ScaleGestureDetector with the supplied listener.
You may only use this constructor from a Looper thread.
| Parameters | |
|---|---|
context |
Context:
the application's context |
listener |
ScaleGestureDetector.OnScaleGestureListener:
the listener invoked for all the callbacks, this must
not be null. |
| Throws | |
|---|---|
NullPointerException |
if listener is null.
|
ScaleGestureDetector (Context context, ScaleGestureDetector.OnScaleGestureListener listener, Handler handler)
Creates a ScaleGestureDetector with the supplied listener.
| Parameters | |
|---|---|
context |
Context:
the application's context |
listener |
ScaleGestureDetector.OnScaleGestureListener:
the listener invoked for all the callbacks, this must
not be null. |
handler |
Handler:
the handler to use for running deferred listener events. |
| Throws | |
|---|---|
NullPointerException |
if listener is null.
|
See also:
float getCurrentSpan ()
Return the average distance between each of the pointers forming the gesture in progress through the focal point.
| Returns | |
|---|---|
float |
Distance between pointers in pixels. |
float getCurrentSpanX ()
Return the average X distance between each of the pointers forming the gesture in progress through the focal point.
| Returns | |
|---|---|
float |
Distance between pointers in pixels. |
float getCurrentSpanY ()
Return the average Y distance between each of the pointers forming the gesture in progress through the focal point.
| Returns | |
|---|---|
float |
Distance between pointers in pixels. |
long getEventTime ()
Return the event time of the current event being processed.
| Returns | |
|---|---|
long |
Current event time in milliseconds. |
float getFocusX ()
Get the X coordinate of the current gesture's focal point.
If a gesture is in progress, the focal point is between
each of the pointers forming the gesture.
If isInProgress() would return false, the result of this
function is undefined.
| Returns | |
|---|---|
float |
X coordinate of the focal point in pixels. |
float getFocusY ()
Get the Y coordinate of the current gesture's focal point.
If a gesture is in progress, the focal point is between
each of the pointers forming the gesture.
If isInProgress() would return false, the result of this
function is undefined.
| Returns | |
|---|---|
float |
Y coordinate of the focal point in pixels. |
float getPreviousSpan ()
Return the previous average distance between each of the pointers forming the gesture in progress through the focal point.
| Returns | |
|---|---|
float |
Previous distance between pointers in pixels. |
float getPreviousSpanX ()
Return the previous average X distance between each of the pointers forming the gesture in progress through the focal point.
| Returns | |
|---|---|
float |
Previous distance between pointers in pixels. |
float getPreviousSpanY ()
Return the previous average Y distance between each of the pointers forming the gesture in progress through the focal point.
| Returns | |
|---|---|
float |
Previous distance between pointers in pixels. |
float getScaleFactor ()
Return the scaling factor from the previous scale event to the current
event. This value is defined as
(getCurrentSpan() / getPreviousSpan()).
| Returns | |
|---|---|
float |
The current scaling factor. |
long getTimeDelta ()
Return the time difference in milliseconds between the previous accepted scaling event and the current scaling event.
| Returns | |
|---|---|
long |
Time difference since the last scaling event in milliseconds. |
boolean isInProgress ()
Returns true if a scale gesture is in progress.
| Returns | |
|---|---|
boolean |
|
boolean isQuickScaleEnabled ()
Return whether the quick scale gesture, in which the user performs a double tap followed by a swipe, should perform scaling. .
| Returns | |
|---|---|
boolean |
|
See also:
boolean isStylusScaleEnabled ()
Return whether the stylus scale gesture, in which the user uses a stylus and presses the button, should perform scaling.
| Returns | |
|---|---|
boolean |
|
See also:
boolean onTouchEvent (MotionEvent event)
Accepts MotionEvents and dispatches events to a ScaleGestureDetector.OnScaleGestureListener
when appropriate.
Applications should pass a complete and consistent event stream to this method. A complete and consistent event stream involves all MotionEvents from the initial ACTION_DOWN to the final ACTION_UP or ACTION_CANCEL.
| Parameters | |
|---|---|
event |
MotionEvent:
The event to process |
| Returns | |
|---|---|
boolean |
true if the event was processed and the detector wants to receive the rest of the MotionEvents in this event stream. |
void setQuickScaleEnabled (boolean scales)
Set whether the associated ScaleGestureDetector.OnScaleGestureListener should receive onScale callbacks
when the user performs a doubleTap followed by a swipe. Note that this is enabled by default
if the app targets API 19 and newer.
| Parameters | |
|---|---|
scales |
boolean:
true to enable quick scaling, false to disable
|
void setStylusScaleEnabled (boolean scales)
Sets whether the associates ScaleGestureDetector.OnScaleGestureListener should receive
onScale callbacks when the user uses a stylus and presses the button.
Note that this is enabled by default if the app targets API 23 and newer.
| Parameters | |
|---|---|
scales |
boolean:
true to enable stylus scaling, false to disable.
|