JavaFX区分拖放

Question

I'm trying to do the following in JavaFX. I am using Canvas to draw stuff on the screen and I want the following to happen:

When I click on the Canvas surface (like fast press and release): something happens

When I drag on the Canvas surface (like press and move, then release): something ELSE happens

BUT I want it to exclude the click action if I drag, so if I drag, what would have happened if I clicked should not happen. Sadly, it seems like when I release the mouse, both release and click events launch, even if I drag.

Answer 1

The method isStillSincePress() can be used together with the getEventType() , both from the MouseEvent API.

Maybe you'll need to implement a threshold for the mouse movement between the MOUSE_PRESSED and MOUSE_RELEASED to improve the usability.

Answer 2

It's a bit late, but in case someone will come here for a solution. I've created a simple class to handle it.

Usage:

clickNotDragDetectingOn(yourNode)
        .withPressedDurationTreshold(150)
        .setOnMouseClickedNotDragged((mouseEvent) -> {
            // logic here
        });

Code:

class MouseClickNotDragDetector {

    private final Node node;

    private Consumer<MouseEvent> onClickedNotDragged;
    private boolean wasDragged;
    private long timePressed;
    private long timeReleased;
    private long pressedDurationTreshold;

    private MouseClickNotDragDetector(Node node) {
        this.node = node;

        node.addEventHandler(MOUSE_PRESSED, (mouseEvent) -> {
            this.timePressed = currentTimeMillis();
        });

        node.addEventHandler(MOUSE_DRAGGED, (mouseEvent) -> {
            this.wasDragged = true;
        });

        node.addEventHandler(MOUSE_RELEASED, (mouseEvent) -> {
            this.timeReleased = currentTimeMillis();
            this.fireEventIfWasClickedNotDragged(mouseEvent);
            this.clear();
        });

        this.pressedDurationTreshold = 200;
    }

    static MouseClickNotDragDetector clickNotDragDetectingOn(Node node) {
        return new MouseClickNotDragDetector(node);
    }

    MouseClickNotDragDetector withPressedDurationTreshold(long durationTreshold) {
        this.pressedDurationTreshold = durationTreshold;
        return this;
    }

    MouseClickNotDragDetector setOnMouseClickedNotDragged(Consumer<MouseEvent> onClickedNotDragged) {
        this.onClickedNotDragged = onClickedNotDragged;
        return this;
    }

    private void clear() {
        this.wasDragged = false;
        this.timePressed = 0;
        this.timeReleased = 0;
    }

    private void fireEventIfWasClickedNotDragged(MouseEvent mouseEvent) {
        if ( this.wasDragged ) {
            debug("[CLICK-NOT-DRAG] dragged!");
            return;
        }
        if ( this.mousePressedDuration() > this.pressedDurationTreshold ) {
            debug("[CLICK-NOT-DRAG] pressed too long, not a click!");
            return;
        }
        debug("[CLICK-NOT-DRAG] click!");
        this.onClickedNotDragged.accept(mouseEvent);
    }

    private long mousePressedDuration() {
        return this.timeReleased - this.timePressed;
    }
}

Answer 3

@wcomnisky

Thank you very much for your help. What I did in the end (I tried using isStillSincePress() in the release event handler and it seemed it was still treating short distance drags as clicks.. though I may have done something wrong) was this: in the mouse press handler I record press coordinates (maybe this idea is similar to the isStillSincePressed() method.. it may have been suggested by its name / description) pressX = event.getX(); pressY = event.getY() pressX = event.getX(); pressY = event.getY() and in the mouse release handler I do this: if( (pressX == event.getX() ) && (pressY == event.getY()) ) doClickAction(); else doDragEndAction() if( (pressX == event.getX() ) && (pressY == event.getY()) ) doClickAction(); else doDragEndAction() . Seems to be workin.. for handling actions while dragging, I'll try using the usual drag handler.