How to make canvas Resizable in javaFX?


Question

In javaFX to resize a canvas there is no such method to do that, the only solution is to extends from Canvas.

class ResizableCanvas extends Canvas {

    public ResizableCanvas() {
        // Redraw canvas when size changes.
        widthProperty().addListener(evt -> draw());
        heightProperty().addListener(evt -> draw());
    }

    private void draw() {
        double width = getWidth();
        double height = getHeight();

        GraphicsContext gc = getGraphicsContext2D();
        gc.clearRect(0, 0, width, height);

    }

    @Override
    public boolean isResizable() {
        return true;
    }
}

is extends from Canvas is the only solution to make canvas Resizable ? because this solution work only if we don't want to use FXML, if we declare in fxml a canvas how can we make it resizable?

this is my code :

package sample;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.layout.AnchorPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class Main extends Application {

    Controller controller;

    @Override
    public void start(Stage primaryStage) throws Exception{
        FXMLLoader loader = new FXMLLoader(getClass().getResource("sample.fxml"));
        AnchorPane root = loader.load(); // controller initialized
        controller = loader.getController();
        GraphicsContext gc = controller.canvas.getGraphicsContext2D();
        gc.setFill(Color.AQUA);
        gc.fillRect(0, 0, root.getPrefWidth(), root.getPrefHeight());
        primaryStage.setTitle("Hello World");
        primaryStage.setScene(new Scene(controller.Pane, controller.Pane.getPrefWidth(), controller.Pane.getPrefHeight()));
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}
1
10
7/22/2019 11:51:15 PM

Accepted Answer

There's a guide that I think that you may find useful for setting up a resizable canvas:

JavaFx tip - resizable canvas

Piece of code from the guide:

/**
 * Tip 1: A canvas resizing itself to the size of
 *        the parent pane.
 */
public class Tip1ResizableCanvas extends Application {

    class ResizableCanvas extends Canvas {

        public ResizableCanvas() {
            // Redraw canvas when size changes.
            widthProperty().addListener(evt -> draw());
            heightProperty().addListener(evt -> draw());
        }

        private void draw() {
            double width = getWidth();
            double height = getHeight();

            GraphicsContext gc = getGraphicsContext2D();
            gc.clearRect(0, 0, width, height);

            gc.setStroke(Color.RED);
            gc.strokeLine(0, 0, width, height);
            gc.strokeLine(0, height, width, 0);
        }

        @Override
        public boolean isResizable() {
            return true;
        }

        @Override
        public double prefWidth(double height) {
            return getWidth();
        }

        @Override
        public double prefHeight(double width) {
            return getHeight();
        }
    }
5
8/11/2015 4:10:33 PM

Taken from http://werner.yellowcouch.org/log/resizable-javafx-canvas/: To make a JavaFx canvas resizable all that needs to be done is override the min/pref/max methods. Make it resizable and implement the resize method.

With this method no width/height listeners are necessary to trigger a redraw. It is also no longer necessary to bind the size of the width and height to the container.

public class ResizableCanvas extends Canvas {

@Override
public double minHeight(double width)
{
    return 64;
}

@Override
public double maxHeight(double width)
{
    return 1000;
}

@Override
public double prefHeight(double width)
{
    return minHeight(width);
}

@Override
public double minWidth(double height)
{
    return 0;
}

@Override
public double maxWidth(double height)
{
    return 10000;
}

@Override
public boolean isResizable()
{
    return true;
}

@Override
public void resize(double width, double height)
{
    super.setWidth(width);
    super.setHeight(height);
    <paint>
}

Licensed under: CC-BY-SA with attribution
Not affiliated with: Stack Overflow
Icon