Module javafx.graphics
Package javafx.scene.input

Class 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

    • Field Detail

      • 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 Detail

      • 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 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
        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.

        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
        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: GestureEvent
        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 GestureEvent
        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 GestureEvent
        Returns:
        the event type