javafx.scene.input

Class ScrollEvent

java.lang.Object

java.util.EventObject

javafx.event.Event

javafx.scene.input.InputEvent

javafx.scene.input.GestureEvent

javafx.scene.input.ScrollEvent

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable

public class ScrollEvent
extends GestureEvent

Scroll event indicates that user performed scrolling by mouse wheel, track pad, touch screen or other similar device.

When the scrolling is produced by a touch gesture (such as dragging a finger over a touch screen), it is surrounded by the SCROLL_STARTED and SCROLL_FINISHED events. Changing number of involved touch points during the scrolling is considered a new gesture, so the pair of SCROLL_FINISHED and SCROLL_STARTED notifications is delivered each time the touchCount changes. When the scrolling is caused by a mouse wheel rotation, only a one-time SCROLL event is delivered, without the started/finished surroundings. If scrolling inertia is active on the given platform, some SCROLL events with isInertia() returning true can come after SCROLL_FINISHED.

The event is delivered to the top-most node picked on the gesture coordinates in time of the gesture start - the whole gesture is delivered to the same node even if the coordinates change during the gesture. For mouse wheel rotation the event is delivered to the top-most node picked on mouse cursor location. The delivery is independent of current focus owner.

The event provides two different types of scrolling values: pixel-based and character/line-based. The basic deltaX and deltaY values give reasonable results when used as number of pixels to scroll (The totalDeltaX and totalDeltaY contain the cumulative values for the whole gesture, zeros for mouse wheel). For scrolling text (or other line-based content as tables) the textDelta values should be used if they are available. The textDeltaXUnits and textDeltaYUnits determine how to interpret the textDeltaX and textDeltaY values. If the units are set to NONE, the text-based values are not available (not provided by the underlying platform) and the pixel-based values need to be used.

As all gestures, scrolling can be direct (performed directly at the concrete coordinates as on touch screen - the center point among all the touches is usually used as the gesture coordinates) or indirect (performed indirectly as on track pad or with mouse - the mouse cursor location is usually used as the gesture coordinates).

For example, scrolling a graphical node can be achieved by following code:

    node.setOnScroll(new EventHandler() {
        @Override public void handle(ScrollEvent event) {
            node.setTranslateX(node.getTranslateX() + event.getDeltaX());
            node.setTranslateY(node.getTranslateY() + event.getDeltaY());
        }
    });

A scroll event handler on text-based component behaving according to system settings on all platforms should contain following logic:

    switch(event.getTextDeltaYUnits()) {
        case LINES:
            // scroll about event.getTextDeltaY() lines 
            break;
        case PAGES:
            // scroll about event.getTextDeltaY() pages
            break;
        case NONE:
            // scroll about event.getDeltaY() pixels
            break;
    }
 

Since:

2.2

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ScrollEvent.HorizontalTextScrollUnits Horizontal text-based scrolling units.
static class	ScrollEvent.VerticalTextScrollUnits Vertical text-based scrolling units.

Field Summary

Fields

Modifier and Type	Field and Description
static EventType<ScrollEvent>	ANY Common supertype for all scroll event types.
static EventType<ScrollEvent>	SCROLL This event occurs when user performs a scrolling action such as rotating mouse wheel or dragging a finger over touch screen.
static EventType<ScrollEvent>	SCROLL_FINISHED This event occurs when a scrolling gesture ends.
static EventType<ScrollEvent>	SCROLL_STARTED This event occurs when a scrolling gesture is detected.

Fields inherited from class javafx.event.Event

consumed, eventType, NULL_SOURCE_TARGET, target

Fields inherited from class java.util.EventObject

source

Method Summary

Methods

Modifier and Type	Method and Description
double	getDeltaX() Gets the horizontal scroll amount.
double	getDeltaY() Gets the vertical scroll amount.
double	getTextDeltaX() Gets the horizontal text-based scroll amount.
ScrollEvent.HorizontalTextScrollUnits	getTextDeltaXUnits() Gets the horizontal scrolling units for text-based scrolling.
double	getTextDeltaY() Gets the vertical text-based scroll amount.
ScrollEvent.VerticalTextScrollUnits	getTextDeltaYUnits() Gets the vertical scrolling units for text-based scrolling.
double	getTotalDeltaX() Gets the cumulative horizontal scroll amount for the whole gesture.
double	getTotalDeltaY() Gets the cumulative vertical scroll amount for the whole gesture.
int	getTouchCount() Gets number of touch points that caused this event.
java.lang.String	toString() Returns a string representation of this ScrollEvent object.

Methods inherited from class javafx.scene.input.GestureEvent

copyFor, getSceneX, getSceneY, getScreenX, getScreenY, getX, getY, isAltDown, isControlDown, isDirect, isInertia, isMetaDown, isShiftDown, isShortcutDown

Methods inherited from class javafx.event.Event

clone, consume, fireEvent, getEventType, getTarget, isConsumed

Methods inherited from class java.util.EventObject

getSource

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

ANY

public static final EventType<ScrollEvent> ANY

Common supertype for all scroll event types.

SCROLL

public static final EventType<ScrollEvent> SCROLL

This event occurs when user performs a scrolling action such as rotating mouse wheel or dragging a finger over touch screen.

SCROLL_STARTED

public static final EventType<ScrollEvent> SCROLL_STARTED

This event occurs when a scrolling gesture is detected. It doesn't occur for mouse wheel scrolling.

SCROLL_FINISHED

public static final EventType<ScrollEvent> SCROLL_FINISHED

This event occurs when a scrolling gesture ends. It doesn't occur for mouse wheel scrolling.

Method Detail

getDeltaX

public double getDeltaX()

Gets the horizontal scroll amount. This value should be interpreted as a number of pixels to scroll. When scrolling a text-based content, the textDeltaX and textDeltaXUnits values should be considered first.

The sign of the value is reversed compared to the coordinate system (when you scroll right, the content actually needs to go left). So the returned value can be simply added to the content's X coordinate.

Returns:

Number of pixels to scroll horizontally.

getDeltaY

public double getDeltaY()

Gets the vertical scroll amount. This value should be interpreted as a number of pixels to scroll. When scrolling a line-based content, the textDeltaY and textDeltaYUnits values should be considered first.

The sign of the value is reversed compared to the coordinate system (when you scroll down, the content actually needs to go up). So the returned value can be simply added to the content's Y coordinate.

Returns:

Number of pixels to scroll vertically.

getTotalDeltaX

public double getTotalDeltaX()

Gets the cumulative horizontal scroll amount for the whole gesture. This value should be interpreted as a number of pixels to scroll relatively to the state at the beginning of the gesture. Contains zeros for mouse wheel scrolling.

The sign of the value is reversed compared to the coordinate system (when you scroll right, the content actually needs to go left). So the returned value can be simply added to the content's X coordinate.

Returns:

Number of pixels scrolled horizontally during the gesture

getTotalDeltaY

public double getTotalDeltaY()

Gets the cumulative vertical scroll amount for the whole gesture. This value should be interpreted as a number of pixels to scroll relatively to the state at the beginning of the gesture. Contains zeros for mouse wheel scrolling.

The sign of the value is reversed compared to the coordinate system (when you scroll down, the content actually needs to go up). So the returned value can be simply added to the content's Y coordinate.

Returns:

Number of pixels to scrolled vertically during the gesture

getTextDeltaXUnits

public ScrollEvent.HorizontalTextScrollUnits getTextDeltaXUnits()

Gets the horizontal scrolling units for text-based scrolling. The returned value indicates how to interpret the getTextDeltaX() value. If the returned value is NONE, the text-based scrolling value is not available and the pixel-based getDeltaX() value needs to be used.

Returns:

the horizontal scrolling units for text-based scrolling

getTextDeltaYUnits

public ScrollEvent.VerticalTextScrollUnits getTextDeltaYUnits()

Gets the vertical scrolling units for text-based scrolling. The returned value indicates how to interpret the getTextDeltaY() value. If the returned value is NONE, the text-based scrolling value is not available and the pixel-based getDeltaY() value needs to be used.

Returns:

the vertical scrolling units for text-based scrolling

getTextDeltaX

public double getTextDeltaX()

Gets the horizontal text-based scroll amount. This value should be interpreted according to the getTextDeltaXUnits() value.

Returns:

Number of units to scroll horizontally, zero if the text-based horizontal scrolling data is not available getTextDeltaXUnits() returns NONE

getTextDeltaY

public double getTextDeltaY()

Gets the vertical text-based scroll amount. This value should be interpreted according to the getTextDeltaYUnits() value.

Returns:

Number of units to scroll vertically, zero if the text-based vertical scrolling data is not available getTextDeltaYUnits() returns NONE

getTouchCount

public int getTouchCount()

Gets number of touch points that caused this event. For non-touch source devices as mouse wheel and for inertia events after gesture finish it returns zero.

Returns:

Number of touch points that caused this event

toString

public java.lang.String toString()

Returns a string representation of this ScrollEvent object.

Overrides:

toString in class GestureEvent

Returns:

a string representation of this ScrollEvent object.