ScaleGestureDetector

Kotlin |Java

open class ScaleGestureDetector

kotlin.Any
↳	android.view.ScaleGestureDetector

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
abstract	`OnScaleGestureListener` The listener for receiving notifications when gestures occur.
open	`SimpleOnScaleGestureListener` A convenience class to extend when you only want to listen for a subset of scaling-related events.

Public constructors
`ScaleGestureDetector(context: Context, listener: ScaleGestureDetector.OnScaleGestureListener)` Creates a ScaleGestureDetector with the supplied listener.
`ScaleGestureDetector(context: Context, listener: ScaleGestureDetector.OnScaleGestureListener, handler: Handler?)` Creates a ScaleGestureDetector with the supplied listener.

Public methods
open Float	`getCurrentSpan()` Return the average distance between each of the pointers forming the gesture in progress through the focal point.
open Float	`getCurrentSpanX()` Return the average X distance between each of the pointers forming the gesture in progress through the focal point.
open Float	`getCurrentSpanY()` Return the average Y distance between each of the pointers forming the gesture in progress through the focal point.
open Long	`getEventTime()` Return the event time of the current event being processed.
open Float	`getFocusX()` Get the X coordinate of the current gesture's focal point.
open Float	`getFocusY()` Get the Y coordinate of the current gesture's focal point.
open Float	`getPreviousSpan()` Return the previous average distance between each of the pointers forming the gesture in progress through the focal point.
open Float	`getPreviousSpanX()` Return the previous average X distance between each of the pointers forming the gesture in progress through the focal point.
open Float	`getPreviousSpanY()` Return the previous average Y distance between each of the pointers forming the gesture in progress through the focal point.
open Float	`getScaleFactor()` Return the scaling factor from the previous scale event to the current event.
open Long	`getTimeDelta()` Return the time difference in milliseconds between the previous accepted scaling event and the current scaling event.
open Boolean	`isInProgress()` Returns `true` if a scale gesture is in progress.
open Boolean	`isQuickScaleEnabled()` Return whether the quick scale gesture, in which the user performs a double tap followed by a swipe, should perform scaling.
open Boolean	`isStylusScaleEnabled()` Return whether the stylus scale gesture, in which the user uses a stylus and presses the button, should perform scaling.
open Boolean	`onTouchEvent(event: MotionEvent)` Accepts MotionEvents and dispatches events to a `OnScaleGestureListener` when appropriate.
open Unit	`setQuickScaleEnabled(scales: Boolean)` Set whether the associated `OnScaleGestureListener` should receive onScale callbacks when the user performs a doubleTap followed by a swipe.
open Unit	`setStylusScaleEnabled(scales: Boolean)` Sets whether the associates `OnScaleGestureListener` should receive onScale callbacks when the user uses a stylus and presses the button.

Public constructors

ScaleGestureDetector

Added in API level 8

ScaleGestureDetector(
    context: Context, 
    listener: ScaleGestureDetector.OnScaleGestureListener)

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.

Exceptions
`java.lang.NullPointerException`	if `listener` is null.

ScaleGestureDetector

Added in API level 19

ScaleGestureDetector(
    context: Context, 
    listener: ScaleGestureDetector.OnScaleGestureListener, 
    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`.

Exceptions
`java.lang.NullPointerException`	if `listener` is null.

See Also

android.os.Handler#Handler()

Public methods

getCurrentSpan

Added in API level 8

open fun getCurrentSpan(): Float

Return the average distance between each of the pointers forming the gesture in progress through the focal point.

Return
`Float`	Distance between pointers in pixels.

getCurrentSpanX

Added in API level 11

open fun getCurrentSpanX(): Float

Return the average X distance between each of the pointers forming the gesture in progress through the focal point.

Return
`Float`	Distance between pointers in pixels.

getCurrentSpanY

Added in API level 11

open fun getCurrentSpanY(): Float

Return the average Y distance between each of the pointers forming the gesture in progress through the focal point.

Return
`Float`	Distance between pointers in pixels.

getEventTime

Added in API level 8

open fun getEventTime(): Long

Return the event time of the current event being processed.

Return
`Long`	Current event time in milliseconds.

getFocusX

Added in API level 8

open fun getFocusX(): Float

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.

Return
`Float`	X coordinate of the focal point in pixels.

getFocusY

Added in API level 8

open fun getFocusY(): Float

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.

Return
`Float`	Y coordinate of the focal point in pixels.

getPreviousSpan

Added in API level 8

open fun getPreviousSpan(): Float

Return the previous average distance between each of the pointers forming the gesture in progress through the focal point.

Return
`Float`	Previous distance between pointers in pixels.

getPreviousSpanX

Added in API level 11

open fun getPreviousSpanX(): Float

Return the previous average X distance between each of the pointers forming the gesture in progress through the focal point.

Return
`Float`	Previous distance between pointers in pixels.

getPreviousSpanY

Added in API level 11

open fun getPreviousSpanY(): Float

Return the previous average Y distance between each of the pointers forming the gesture in progress through the focal point.

Return
`Float`	Previous distance between pointers in pixels.

getScaleFactor

Added in API level 8

open fun getScaleFactor(): Float

Return the scaling factor from the previous scale event to the current event. This value is defined as (getCurrentSpan() / getPreviousSpan()).

Return
`Float`	The current scaling factor.

getTimeDelta

Added in API level 8

open fun getTimeDelta(): Long

Return the time difference in milliseconds between the previous accepted scaling event and the current scaling event.

Return
`Long`	Time difference since the last scaling event in milliseconds.

isInProgress

Added in API level 8

open fun isInProgress(): Boolean

Returns true if a scale gesture is in progress.

isQuickScaleEnabled

Added in API level 19

open fun isQuickScaleEnabled(): Boolean

Return whether the quick scale gesture, in which the user performs a double tap followed by a swipe, should perform scaling. {@see #setQuickScaleEnabled(boolean)}.

isStylusScaleEnabled

Added in API level 23

open fun isStylusScaleEnabled(): Boolean

Return whether the stylus scale gesture, in which the user uses a stylus and presses the button, should perform scaling. {@see #setStylusScaleEnabled(boolean)}

onTouchEvent

Added in API level 8

open fun onTouchEvent(event: MotionEvent): Boolean

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`.

Return
`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

open fun setQuickScaleEnabled(scales: Boolean): Unit

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

open fun setStylusScaleEnabled(scales: Boolean): Unit

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.