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 associated `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 associated 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.