自动调整Canvas大小以填充封闭的Parent

Question

我最近想在JavaFX中创建一个动画背景,类似于这里看到的Swing示例.我使用了一个Canvas绘制的内容,如使用Canvas API所示,以及一个AnimationTimer绘图循环,如动画基础知识所示.不幸的是,我不确定如何在调整Canvas封闭Stage大小时自动调整大小.什么是好方法？

Answer 1

在下面的示例中,静态嵌套类CanvasPane包装Canvasa Pane和覆盖中的实例layoutChildren()以使画布尺寸与封闭匹配Pane.请注意,Canvas返回false时isResizable(),"父级无法在布局期间调整大小",并且Pane"除了将可调整大小的子级调整为其首选大小外,不执行布局".的width和height用于构建画布成为其初始大小.在Ensemble粒子模拟中使用类似的方法Fireworks.java来缩放背景图像,同时保持其纵横比.

另外,请注意与使用完全饱和的颜色相比,与原始颜色的区别.这些相关示例说明了在动画背景上放置控件.

import java.util.LinkedList;
import java.util.Queue;
import java.util.Random;
import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.beans.Observable;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.control.CheckBox;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

/**
 * @see https://stackoverflow.com/a/31761362/230513
 * @see https://stackoverflow.com/a/8616169/230513
 */

public class Baubles extends Application {

    private static final int MAX = 64;
    private static final double WIDTH = 640;
    private static final double HEIGHT = 480;
    private static final Random RND = new Random();
    private final Queue<Bauble> queue = new LinkedList<>();
    private Canvas canvas;

    @Override
    public void start(Stage stage) {
        CanvasPane canvasPane = new CanvasPane(WIDTH, HEIGHT);
        canvas = canvasPane.getCanvas();
        BorderPane root = new BorderPane(canvasPane);
        CheckBox cb = new CheckBox("Animate");
        cb.setSelected(true);
        root.setBottom(cb);
        Scene scene = new Scene(root);
        stage.setScene(scene);
        stage.show();

        for (int i = 0; i < MAX; i++) {
            queue.add(randomBauble());
        }
        AnimationTimer loop = new AnimationTimer() {
            @Override
            public void handle(long now) {
                GraphicsContext g = canvas.getGraphicsContext2D();
                g.setFill(Color.BLACK);
                g.fillRect(0, 0, canvas.getWidth(), canvas.getHeight());
                for (Bauble b : queue) {
                    g.setFill(b.c);
                    g.fillOval(b.x, b.y, b.d, b.d);
                }
                queue.add(randomBauble());
                queue.remove();
            }
        };
        loop.start();
        cb.selectedProperty().addListener((Observable o) -> {
            if (cb.isSelected()) {
                loop.start();
            } else {
                loop.stop();
            }
        });
    }

    private static class Bauble {

        private final double x, y, d;
        private final Color c;

        public Bauble(double x, double y, double r, Color c) {
            this.x = x - r;
            this.y = y - r;
            this.d = 2 * r;
            this.c = c;
        }
    }

    private Bauble randomBauble() {
        double x = RND.nextDouble() * canvas.getWidth();
        double y = RND.nextDouble() * canvas.getHeight();
        double r = RND.nextDouble() * MAX + MAX / 2;
        Color c = Color.hsb(RND.nextDouble() * 360, 1, 1, 0.75);
        return new Bauble(x, y, r, c);
    }

    private static class CanvasPane extends Pane {

        private final Canvas canvas;

        public CanvasPane(double width, double height) {
            canvas = new Canvas(width, height);
            getChildren().add(canvas);
        }

        public Canvas getCanvas() {
            return canvas;
        }

        @Override
        protected void layoutChildren() {
            super.layoutChildren();
            final double x = snappedLeftInset();
            final double y = snappedTopInset();
            // Java 9 - snapSize is deprecated, use snapSizeX() and snapSizeY() accordingly
            final double w = snapSize(getWidth()) - x - snappedRightInset();
            final double h = snapSize(getHeight()) - y - snappedBottomInset();
            canvas.setLayoutX(x);
            canvas.setLayoutY(y);
            canvas.setWidth(w);
            canvas.setHeight(h);
        }
    }

    public static void main(String[] args) {
        launch(args);
    }
}

Answer 2

你不能用 a 来做这个Binding吗？以下似乎无需添加派生类即可产生相同的结果。

import java.util.LinkedList;
import java.util.Queue;
import java.util.Random;
import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.beans.Observable;
import javafx.beans.binding.DoubleBinding;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.control.CheckBox;
import javafx.scene.layout.BorderPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

/**
 * @see http://stackoverflow.com/a/31761362/230513
 * @see http://stackoverflow.com/a/8616169/230513
 */

public class Baubles extends Application {

private static final int MAX = 64;
private static final double WIDTH = 640;
private static final double HEIGHT = 480;
private static final Random RND = new Random();
private final Queue<Bauble> queue = new LinkedList<>();
private Canvas canvas;

@Override
public void start(Stage stage) {
    canvas = new Canvas(WIDTH, HEIGHT);
    BorderPane root = new BorderPane(canvas);
    CheckBox cb = new CheckBox("Animate");
    cb.setSelected(true);
    root.setBottom(cb);
    Scene scene = new Scene(root);
    stage.setScene(scene);
    stage.show();

    // Create bindings for resizing.
    DoubleBinding heightBinding = root.heightProperty()
            .subtract(root.bottomProperty().getValue().getBoundsInParent().getHeight());
    canvas.widthProperty().bind(root.widthProperty());
    canvas.heightProperty().bind(heightBinding);

    for (int i = 0; i < MAX; i++) {
        queue.add(randomBauble());
    }
    AnimationTimer loop = new AnimationTimer() {
        @Override
        public void handle(long now) {
            GraphicsContext g = canvas.getGraphicsContext2D();
            g.setFill(Color.BLACK);
            g.fillRect(0, 0, canvas.getWidth(), canvas.getHeight());
            for (Bauble b : queue) {
                g.setFill(b.c);
                g.fillOval(b.x, b.y, b.d, b.d);
            }
            queue.add(randomBauble());
            queue.remove();
        }
    };
    loop.start();
    cb.selectedProperty().addListener((Observable o) -> {
        if (cb.isSelected()) {
            loop.start();
        } else {
            loop.stop();
        }
    });
}

private static class Bauble {

    private final double x, y, d;
    private final Color c;

    public Bauble(double x, double y, double r, Color c) {
        this.x = x - r;
        this.y = y - r;
        this.d = 2 * r;
        this.c = c;
    }
}

private Bauble randomBauble() {
    double x = RND.nextDouble() * canvas.getWidth();
    double y = RND.nextDouble() * canvas.getHeight();
    double r = RND.nextDouble() * MAX + MAX / 2;
    Color c = Color.hsb(RND.nextDouble() * 360, 1, 1, 0.75);
    return new Bauble(x, y, r, c);
}

public static void main(String[] args) {
    launch(args);
}
}

Answer 3

我通过将画布放入窗格中并将其绑定到它来组合之前的两个解决方案（@trashgod 和 @clataq's）：

private static class CanvasPane extends Pane {

    final Canvas canvas;

    CanvasPane(double width, double height) {
        setWidth(width);
        setHeight(height);
        canvas = new Canvas(width, height);
        getChildren().add(canvas);

        canvas.widthProperty().bind(this.widthProperty());
        canvas.heightProperty().bind(this.heightProperty());
    }
}