CODEWITHSUNDEEP
javajavafx
Carter Brainerd
Carter Brainerd

Reputation: 197

How do I implement drag and drop on a canvas?

More specifically, how would I go about implementing a drag and drop feature so that the image file dragged on to the canvas would be drawn on the canvas? I've tried using a VBox listener on top of the canvas, but that didn't work. The source code of by program is available here.

In my controllers initialize() function, I have the following code. canvas is passed from the FXML file via the @FXML annotation:

public void initialize() {
        GraphicsContext g = canvas.getGraphicsContext2D();

        // Setter for brush type
        setBrushBrush();

        // Get screen dimensions and set the canvas accordingly
        Dimension screenSize = getScreenSize();
        double screenWidth = screenSize.getWidth();
        double screenHeight = screenSize.getHeight();
        canvas.setHeight(screenHeight/1.5);
        canvas.setWidth(screenWidth/1.5);

        canvas.setOnMouseDragged(e -> {
         //Drawing code here
        }); 

        canvas.setOnDragOver(e -> {
         // Need to read data of dragged image
        });

        canvas.setOnMouseDragReleased(e -> {
         // Need to put dragged data on to canvas
        });
}

Upvotes: 0

Views: 1212

Answers (1)

James_D
James_D

Reputation: 209330

The mouseDragReleased event is the wrong event to listen for here. That event is triggered when the mouse is released during a "full press-drag-release gesture" within the application; not when data is dropped during a "platform-supported drag-and-drop gesture" (see the documentation for MouseEvent for a description of these different dragging modes). So instead of canvas.setOnMouseDragReleased(...), you need:

canvas.setOnDragDropped(e -> {
    // ...
});

Assuming the implementations of the handlers are correct, this should enable you to drop an image from a file and draw it on the canvas.

Upvotes: 2

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