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ScaleGestureDetector

public class ScaleGestureDetector
extends Object

java.lang.Object
↳	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
`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 timeout, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void`	`wait(long timeout)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void`	`wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

Public constructors

ScaleGestureDetector

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
`listener`	`ScaleGestureDetector.OnScaleGestureListener`: the listener invoked for all the callbacks, this must not be null.

Throws
`NullPointerException`	if `listener` is null.

ScaleGestureDetector

public 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:

Handler.Handler()

Public methods

getCurrentSpan

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

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

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

public long getEventTime ()

Return the event time of the current event being processed.

Returns
`long`	Current event time in milliseconds.

getFocusX

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

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

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

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

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

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

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

public boolean isInProgress ()

Returns true if a scale gesture is in progress.

Returns
`boolean`

isQuickScaleEnabled

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

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

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

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

setQuickScaleEnabled

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

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.

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ScaleGestureDetector

Summary

Nested classes

Public constructors

Public methods

Inherited methods

Public constructors

ScaleGestureDetector

ScaleGestureDetector

Public methods

getCurrentSpan

getCurrentSpanX

getCurrentSpanY

getEventTime

getFocusX

getFocusY

getPreviousSpan

getPreviousSpanX

getPreviousSpanY

getScaleFactor

getTimeDelta

isInProgress

isQuickScaleEnabled

isStylusScaleEnabled

onTouchEvent

setQuickScaleEnabled

setStylusScaleEnabled