com.luciad.input.touch

Class TouchGestureRecognizer

java.lang.Object

com.luciad.input.touch.TouchGestureRecognizer

All Implemented Interfaces:

AutoCloseable

public final class TouchGestureRecognizer
extends Object
implements AutoCloseable

This class generates high-level touch gesture events from low-level input events.

High level events are subclasses of IInputEvent such as TouchTapEvent. Sequences of low level events are used to create those high level events.

For example, a touch press + movement of the touch point (possibly multiple times) sequence is recognized as a touch drag gesture. A touch press + a touch release sequence is recognized as a touch tap gesture. This class is useful when adding integration with a platform that does not provide these more high-level events.

A typical use of such a class is to wire it to a UI framework specific class (such as Qt , see QQuickMapObject in the sample code) and make the controller react to the high level event instead of every low level event the framework can fire.

The use of the TouchGestureRecognizer is optional. A controller implementation can use custom conversion code if needed, for example if you want to manage the low level events yourself and create other high level IInputEvent instances.

The events passed to this class are expected to be defined in device independent pixels.

Constructor Summary

Constructors

Constructor and Description
TouchGestureRecognizer(IInputEventCallback callback, ITaskScheduler taskScheduler) Creates a TouchGestureRecognizer The generated high level IInputEvents are passed to the given callback on the UI thread.

Method Summary

Modifier and Type	Method and Description
void	close()
protected void	finalize()
double	getDisplayScale()
double	getDpi()
ScreenDistance	getDragThreshold()
long	getLongPressThreshold()
long	getMultiTapInterval()
ScreenDistance	getMultiTapThreshold()
void	onTouchEvent(TouchPointEvent touchPointEvent) Entry point for the touch events of the gesture recognizer.
void	setDisplayScale(double scale) Set the display scale factor.
void	setDpi(double dpi) Set the display pixel density in dots per inch.
void	setDragThreshold(ScreenDistance threshold) Sets the screen distance that is used as threshold to detect if a drag is performed while using touch inputs.
void	setLongPressThreshold(long longPressThreshold) Set the threshold, in milliseconds, to reach before a long press event is sent.
void	setMultiTapInterval(long interval) Set the interval used to detect multiple taps (default is 400 ms).
void	setMultiTapThreshold(ScreenDistance threshold) Set the screen distance threshold to detect multiple taps.

Methods inherited from class java.lang.Object

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

Constructor Detail

TouchGestureRecognizer

public TouchGestureRecognizer(@NotNull
                              IInputEventCallback callback,
                              @Nullable
                              ITaskScheduler taskScheduler)
                       throws NullPointerException

Creates a TouchGestureRecognizer The generated high level IInputEvents are passed to the given callback on the UI thread.

For certain events, like for example a long press, an internal timer is used to determine when an IInputEvent needs to be sent. Due to the use of a timer, it is possible that some work is done on a different thread than the UI thread. The task scheduler can be used to apply the result of the timer on the UI thread.

Parameters:

callback - the callback that receive generated IInputEvents. Can not be null.

taskScheduler - a scheduler allowing the caller to receive some IInputEvents on another thread and resolve them on the UI thread. Can be null. If null, some events won't be emitted.

Throws:

NullPointerException - If callback is null.

Method Detail

finalize

protected void finalize()

Overrides:

finalize in class Object

close

public void close()

Specified by:

close in interface AutoCloseable

onTouchEvent

public void onTouchEvent(@NotNull
                         TouchPointEvent touchPointEvent)

Entry point for the touch events of the gesture recognizer.

Parameters:

touchPointEvent - the TouchPointEvent object containing a collection of TouchPoints.

setMultiTapInterval

public void setMultiTapInterval(long interval)

Set the interval used to detect multiple taps (default is 400 ms).

Parameters:

interval - the maximum time (in milliseconds) between multiple taps. If the interval is set to 0, no multiple taps will be detected.

getMultiTapInterval

public long getMultiTapInterval()

Returns:

the time interval used to detect multiple taps, expressed in milliseconds (default is 400 ms).

setDragThreshold

public void setDragThreshold(@NotNull
                             ScreenDistance threshold)

Sets the screen distance that is used as threshold to detect if a drag is performed while using touch inputs.

It means that the input device has to move at least that distance before it can be detected as a drag gesture. The default drag threshold is a screen distance of 5 mm.

Parameters:

threshold - the screen distance threshold

getDragThreshold

@NotNull
public ScreenDistance getDragThreshold()

Returns:

the screen distance that is used as threshold to detect if a drag is performed while using touch inputs. It means that the input device has to move at least that amount of pixels before it can be detected as a drag gesture.

setMultiTapThreshold

public void setMultiTapThreshold(@NotNull
                                 ScreenDistance threshold)

Set the screen distance threshold to detect multiple taps.

It means that consecutive taps need to be as close as that distance in order to generate an event for a multiple tap.

Parameters:

threshold - the distance threshold

getMultiTapThreshold

@NotNull
public ScreenDistance getMultiTapThreshold()

Returns:

the screen distance threshold for multiple taps detection.

setLongPressThreshold

public void setLongPressThreshold(long longPressThreshold)

Set the threshold, in milliseconds, to reach before a long press event is sent.

The default is 700 ms.

Parameters:

longPressThreshold - the threshold in milliseconds.

getLongPressThreshold

public long getLongPressThreshold()

Returns:

the threshold, in milliseconds, to reach before a long press event is sent.

setDpi

public void setDpi(double dpi)

Set the display pixel density in dots per inch.

If no value is provided, the platform standard pixel density is assumed.

Parameters:

dpi - the pixel density in dots per inch

getDpi

public double getDpi()

Returns:

the display pixel density, expressed in dots per inch.

setDisplayScale

public void setDisplayScale(double scale)

Set the display scale factor.

If no value is provided, a scale factor of 1.0 is assumed.

Parameters:

scale - the display scale factor (adimensional scale value)

getDisplayScale

public double getDisplayScale()

Returns:

the display scale factor.