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:
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:

  • 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.

      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 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