com.telerik.widget.chart.visualization.behaviors

Class ChartScaleGestureDetector

java.lang.Object

com.telerik.widget.chart.visualization.behaviors.ChartScaleGestureDetector

public class ChartScaleGestureDetector
extends Object

Detects scaling transformation gestures using the supplied MotionEvents. The ChartScaleGestureDetector.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(MotionEvent). The methods defined in your callback will be executed when the events occur.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	ChartScaleGestureDetector.OnScaleGestureListener The listener for receiving notifications when gestures occur.
static class	ChartScaleGestureDetector.SimpleOnScaleGestureListener A convenience class to extend when you only want to listen for a subset of scaling-related events.

Constructor Summary

Constructors

Constructor and Description
ChartScaleGestureDetector(Context context, ChartScaleGestureDetector.OnScaleGestureListener listener) Creates a ScaleGestureDetector with the supplied listener.
ChartScaleGestureDetector(Context context, ChartScaleGestureDetector.OnScaleGestureListener listener, Handler handler) Creates a ScaleGestureDetector with the supplied listener.

Method Summary

Modifier and Type	Method and Description
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	onTouchEvent(MotionEvent event) Accepts MotionEvents and dispatches events to a ChartScaleGestureDetector.OnScaleGestureListener when appropriate.
void	setQuickScaleEnabled(boolean scales) Set whether the associated ChartScaleGestureDetector.OnScaleGestureListener should receive onScale callbacks when the user performs a doubleTap followed by a swipe.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ChartScaleGestureDetector

public ChartScaleGestureDetector(Context context,
                                 ChartScaleGestureDetector.OnScaleGestureListener listener)

Creates a ScaleGestureDetector with the supplied listener. You may only use this constructor from a Looper thread.

Parameters:

context - the application's context

listener - the listener invoked for all the callbacks, this must not be null.

Throws:

NullPointerException - if listener is null.

ChartScaleGestureDetector

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

Creates a ScaleGestureDetector with the supplied listener.

Parameters:

context - the application's context

listener - the listener invoked for all the callbacks, this must not be null.

handler - the handler to use for running deferred listener events.

Throws:

NullPointerException - if listener is null.

See Also:

Handler.Handler()

Method Detail

onTouchEvent

public boolean onTouchEvent(MotionEvent event)

Accepts MotionEvents and dispatches events to a ChartScaleGestureDetector.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 - The event to process

Returns:

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 ChartScaleGestureDetector.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 - true to enable quick scaling, false to disable

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.

See Also:

setQuickScaleEnabled(boolean)

isInProgress

public boolean isInProgress()

Returns true if a scale gesture is in progress.

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:

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:

Y coordinate of the focal point in pixels.

getCurrentSpan

public float getCurrentSpan()

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

Returns:

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:

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:

Distance between pointers 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:

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:

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:

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:

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:

Time difference since the last scaling event in milliseconds.

getEventTime

public long getEventTime()

Return the event time of the current event being processed.

Returns:

Current event time in milliseconds.