Class ScrollEvent

javafx.scene.input.ScrollEvent

All Implemented Interfaces:: Serializable, Cloneable

public final 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<ScrollEvent>() {
        @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:: JavaFX 2.0
See Also:: Serialized Form

Nested Class Summary

Nested Classes
Modifier and Type	Class	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	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 declared in class javafx.event.Event

consumed, eventType, NULL_SOURCE_TARGET, target

Fields declared in class java.util.EventObject

source

Constructor Summary

Constructors
Constructor	Description
ScrollEvent(Object source, EventTarget target, EventType<ScrollEvent> eventType, double x, double y, double screenX, double screenY, boolean shiftDown, boolean controlDown, boolean altDown, boolean metaDown, boolean direct, boolean inertia, double deltaX, double deltaY, double totalDeltaX, double totalDeltaY, ScrollEvent.HorizontalTextScrollUnits textDeltaXUnits, double textDeltaX, ScrollEvent.VerticalTextScrollUnits textDeltaYUnits, double textDeltaY, int touchCount, PickResult pickResult)	Constructs new ScrollEvent event.
ScrollEvent(EventType<ScrollEvent> eventType, double x, double y, double screenX, double screenY, boolean shiftDown, boolean controlDown, boolean altDown, boolean metaDown, boolean direct, boolean inertia, double deltaX, double deltaY, double totalDeltaX, double totalDeltaY, double multiplierX, double multiplierY, ScrollEvent.HorizontalTextScrollUnits textDeltaXUnits, double textDeltaX, ScrollEvent.VerticalTextScrollUnits textDeltaYUnits, double textDeltaY, int touchCount, PickResult pickResult)	Constructs new ScrollEvent event with null source and target
`ScrollEvent(EventType<ScrollEvent> eventType, double x, double y, double screenX, double screenY, boolean shiftDown, boolean controlDown, boolean altDown, boolean metaDown, boolean direct, boolean inertia, double deltaX, double deltaY, double totalDeltaX, double totalDeltaY, ScrollEvent.HorizontalTextScrollUnits textDeltaXUnits, double textDeltaX, ScrollEvent.VerticalTextScrollUnits textDeltaYUnits, double textDeltaY, int touchCount, PickResult pickResult)`	Constructs new ScrollEvent event with null source and target

Method Summary

Modifier and Type	Method	Description
`ScrollEvent`	`copyFor(Object newSource, EventTarget newTarget)`	Creates and returns a copy of this event with the specified event source and target.
`ScrollEvent`	`copyFor(Object newSource, EventTarget newTarget, EventType<ScrollEvent> type)`	Creates a copy of the given event with the given fields substituted.
`double`	`getDeltaX()`	Gets the horizontal scroll amount.
`double`	`getDeltaY()`	Gets the vertical scroll amount.
`EventType<ScrollEvent>`	`getEventType()`	Gets the event type of this event.
`double`	`getMultiplierX()`	Gets the multiplier used to convert mouse wheel rotation units to pixels
`double`	`getMultiplierY()`	Gets the multiplier used to convert mouse wheel rotation units to pixels
`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.
`String`	`toString()`	Returns a string representation of this `ScrollEvent` object.

Methods declared in class javafx.scene.input.GestureEvent

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

Methods declared in class javafx.event.Event

clone, consume, fireEvent, getTarget, isConsumed

Methods declared in class java.util.EventObject

getSource

Methods declared in class java.lang.Object

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

Field Details

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.

Since:: JavaFX 2.2

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.

Since:: JavaFX 2.2

Constructor Details

ScrollEvent

public ScrollEvent(Object source, EventTarget target, EventType<ScrollEvent> eventType, double x, double y, double screenX, double screenY, boolean shiftDown, boolean controlDown, boolean altDown, boolean metaDown, boolean direct, boolean inertia, double deltaX, double deltaY, double totalDeltaX, double totalDeltaY, ScrollEvent.HorizontalTextScrollUnits textDeltaXUnits, double textDeltaX, ScrollEvent.VerticalTextScrollUnits textDeltaYUnits, double textDeltaY, int touchCount, PickResult pickResult)

Constructs new ScrollEvent event.

Parameters:: source - the source of the event. Can be null.; target - the target of the event. Can be null.; eventType - The type of the event.; x - The x with respect to the scene.; y - The y with respect to the scene.; screenX - The x coordinate relative to screen.; screenY - The y coordinate relative to screen.; shiftDown - true if shift modifier was pressed.; controlDown - true if control modifier was pressed.; altDown - true if alt modifier was pressed.; metaDown - true if meta modifier was pressed.; direct - true if the event was caused by direct input device. See GestureEvent.isDirect(); inertia - if represents inertia of an already finished gesture.; deltaX - horizontal scroll amount; deltaY - vertical scroll amount; totalDeltaX - cumulative horizontal scroll amount; totalDeltaY - cumulative vertical scroll amount; textDeltaXUnits - units for horizontal text-based scroll amount; textDeltaX - horizontal text-based scroll amount; textDeltaYUnits - units for vertical text-based scroll amount; textDeltaY - vertical text-based scroll amount; touchCount - number of touch points; pickResult - pick result. Can be null, in this case a 2D pick result without any further values is constructed based on the scene coordinates and the target
Since:: JavaFX 8.0

ScrollEvent

public ScrollEvent(EventType<ScrollEvent> eventType, double x, double y, double screenX, double screenY, boolean shiftDown, boolean controlDown, boolean altDown, boolean metaDown, boolean direct, boolean inertia, double deltaX, double deltaY, double totalDeltaX, double totalDeltaY, ScrollEvent.HorizontalTextScrollUnits textDeltaXUnits, double textDeltaX, ScrollEvent.VerticalTextScrollUnits textDeltaYUnits, double textDeltaY, int touchCount, PickResult pickResult)

Constructs new ScrollEvent event with null source and target

Parameters:: eventType - The type of the event.; x - The x with respect to the scene.; y - The y with respect to the scene.; screenX - The x coordinate relative to screen.; screenY - The y coordinate relative to screen.; shiftDown - true if shift modifier was pressed.; controlDown - true if control modifier was pressed.; altDown - true if alt modifier was pressed.; metaDown - true if meta modifier was pressed.; direct - true if the event was caused by direct input device. See GestureEvent.isDirect(); inertia - if represents inertia of an already finished gesture.; deltaX - horizontal scroll amount; deltaY - vertical scroll amount; totalDeltaX - cumulative horizontal scroll amount; totalDeltaY - cumulative vertical scroll amount; textDeltaXUnits - units for horizontal text-based scroll amount; textDeltaX - horizontal text-based scroll amount; textDeltaYUnits - units for vertical text-based scroll amount; textDeltaY - vertical text-based scroll amount; touchCount - number of touch points; pickResult - pick result. Can be null, in this case a 2D pick result without any further values is constructed based on the scene coordinates
Since:: JavaFX 8.0

ScrollEvent

public ScrollEvent(EventType<ScrollEvent> eventType, double x, double y, double screenX, double screenY, boolean shiftDown, boolean controlDown, boolean altDown, boolean metaDown, boolean direct, boolean inertia, double deltaX, double deltaY, double totalDeltaX, double totalDeltaY, double multiplierX, double multiplierY, ScrollEvent.HorizontalTextScrollUnits textDeltaXUnits, double textDeltaX, ScrollEvent.VerticalTextScrollUnits textDeltaYUnits, double textDeltaY, int touchCount, PickResult pickResult)

Constructs new ScrollEvent event with null source and target

Parameters:: eventType - The type of the event.; x - The x with respect to the scene.; y - The y with respect to the scene.; screenX - The x coordinate relative to screen.; screenY - The y coordinate relative to screen.; shiftDown - true if shift modifier was pressed.; controlDown - true if control modifier was pressed.; altDown - true if alt modifier was pressed.; metaDown - true if meta modifier was pressed.; direct - true if the event was caused by direct input device. See GestureEvent.isDirect(); inertia - if represents inertia of an already finished gesture.; deltaX - horizontal scroll amount; deltaY - vertical scroll amount; totalDeltaX - cumulative horizontal scroll amount; totalDeltaY - cumulative vertical scroll amount; multiplierX - an X multiplier used to convert wheel rotations to pixels; multiplierY - an Y multiplier used to convert wheel rotations to pixels; textDeltaXUnits - units for horizontal text-based scroll amount; textDeltaX - horizontal text-based scroll amount; textDeltaYUnits - units for vertical text-based scroll amount; textDeltaY - vertical text-based scroll amount; touchCount - number of touch points; pickResult - pick result. Can be null, in this case a 2D pick result without any further values is constructed based on the scene coordinates
Since:: JavaFX 8.0

Method Details

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.

Returns:: Number of pixels scrolled horizontally during the gesture
Since:: JavaFX 2.2

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.

Returns:: Number of pixels to scrolled vertically during the gesture
Since:: JavaFX 2.2

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
Since:: JavaFX 2.2

getMultiplierX

public double getMultiplierX()

Gets the multiplier used to convert mouse wheel rotation units to pixels

Returns:: the x multiplier
Since:: JavaFX 8.0

getMultiplierY

public double getMultiplierY()

Gets the multiplier used to convert mouse wheel rotation units to pixels

Returns:: the y multiplier
Since:: JavaFX 8.0

toString

public String toString()

Returns a string representation of this ScrollEvent object.

Overrides:: toString in class GestureEvent
Returns:: a string representation of this ScrollEvent object.

copyFor

public ScrollEvent copyFor(Object newSource, EventTarget newTarget)

Description copied from class: Event

Creates and returns a copy of this event with the specified event source and target. If the source or target is set to null, it is replaced by the NULL_SOURCE_TARGET value.

Overrides:: copyFor in class Event
Parameters:: newSource - the new source of the copied event; newTarget - the new target of the copied event
Returns:: the event copy with the new source and target

copyFor

public ScrollEvent copyFor(Object newSource, EventTarget newTarget, EventType<ScrollEvent> type)

Creates a copy of the given event with the given fields substituted.

Parameters:: newSource - the new source of the copied event; newTarget - the new target of the copied event; type - the new eventType
Returns:: the event copy with the fields substituted
Since:: JavaFX 8.0

getEventType

public EventType<ScrollEvent> getEventType()

Description copied from class: Event

Gets the event type of this event. Objects of the same Event class can have different event types. These event types further specify what kind of event occurred.

Overrides:: getEventType in class Event
Returns:: the event type

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