Added in API level 8

Summary: Nested Classes | Ctors | Methods | Inherited Methods

ScaleGestureDetector

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Kotlin |Java

public class ScaleGestureDetector
extends Object

java.lang.Object
↳	android.view.ScaleGestureDetector

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Detects scaling transformation gestures using the supplied MotionEvents. The 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:

• Create an instance of the ScaleGestureDetector for your View
• In the View#onTouchEvent(MotionEvent) method ensure you call onTouchEvent(android.view.MotionEvent). The methods defined in your callback will be executed when the events occur.

Summary

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 true if a scale gesture is in progress.
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 OnScaleGestureListener when appropriate.
void	setQuickScaleEnabled(boolean scales) Set whether the associated OnScaleGestureListener should receive onScale callbacks when the user performs a doubleTap followed by a swipe.
void	setStylusScaleEnabled(boolean scales) Sets whether the associates OnScaleGestureListener should receive onScale callbacks when the user uses a stylus and presses the button.

Inherited methods

From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public constructors

ScaleGestureDetector

Added in API level 8

public 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 This value cannot be null.
listener	ScaleGestureDetector.OnScaleGestureListener: the listener invoked for all the callbacks, this must not be null.

Throws
NullPointerException	if listener is null.

ScaleGestureDetector

Added in API level 19

public ScaleGestureDetector (Context context, 
                ScaleGestureDetector.OnScaleGestureListener listener, 
                Handler handler)

Creates a ScaleGestureDetector with the supplied listener.

Parameters
context	Context: the application's context This value cannot be null.
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. This value may be null.

Throws
NullPointerException	if listener is null.

See also:

• Handler.Handler()

Public methods

getCurrentSpan

Added in API level 8

public 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.

getCurrentSpanX

Added in API level 11

public 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.

getCurrentSpanY

Added in API level 11

public 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.

getEventTime

Added in API level 8

public long getEventTime ()

Return the event time of the current event being processed.

Returns
long	Current event time in milliseconds.

getFocusX

Added in API level 8

public 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.

getFocusY

Added in API level 8

public 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.

getPreviousSpan

Added in API level 8

public 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.

getPreviousSpanX

Added in API level 11

public 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.

getPreviousSpanY

Added in API level 11

public 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.

getScaleFactor

Added in API level 8

public 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.

getTimeDelta

Added in API level 8

public 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.

isInProgress

Added in API level 8

public boolean isInProgress ()

Returns true if a scale gesture is in progress.

Returns
boolean

isQuickScaleEnabled

Added in API level 19

public 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:

• setQuickScaleEnabled(boolean)

isStylusScaleEnabled

Added in API level 23

public 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:

• setStylusScaleEnabled(boolean)

onTouchEvent

Added in API level 8

public boolean onTouchEvent (MotionEvent event)

Accepts MotionEvents and dispatches events to a 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 This value cannot be null.

Returns
boolean	true if the event was processed and the detector wants to receive the rest of the MotionEvents in this event stream.

setQuickScaleEnabled

Added in API level 19

public void setQuickScaleEnabled (boolean scales)

Set whether the associated 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

setStylusScaleEnabled

Added in API level 23

public void setStylusScaleEnabled (boolean scales)

Sets whether the associates 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.