java - 使用 JLayer 阻止对 Canvas 的输入

Question

我正在尝试编写利用JLayer来阻止事件进入由该层装饰的组件的代码。但是，我无法找到一种方法来做到这一点。

Here is a SSCCE 。这是一个pastebin链接，因为当我尝试使用它时，代码插入总是会破坏格式。

public class Window extends JFrame{

    private static boolean blockInput = true;
    private CustomCanvas canvas = new CustomCanvas();

    public static void main(String[] args) {
    new Window().setVisible(true);
    }

    public Window() {
    canvas.addMouseListener(canvas);
    LayerUI<Canvas> layerUI = new CanvasLayerUI();
    JLayer<Canvas> canvasLayer = new JLayer<Canvas>(canvas, layerUI);
    add(canvasLayer);
    setSize(800, 600);
    }

    private class CanvasLayerUI extends LayerUI<Canvas> {

    @Override
    public void eventDispatched(AWTEvent e, JLayer<? extends Canvas> l) {
        if (blockInput) {
        if (e instanceof InputEvent) {
            ((InputEvent) e).consume();
        }
        } else {
        super.eventDispatched(e, l);
        }
    }

    @Override
    public void installUI(JComponent c) {
        super.installUI(c);
        if (c instanceof JLayer) {
        JLayer<?> layer = (JLayer<?>) c;
        layer.setLayerEventMask(AWTEvent.MOUSE_EVENT_MASK);
        }
    }

    @Override
    protected void processMouseEvent(MouseEvent e, JLayer<? extends Canvas> l) {
        super.processMouseEvent(e, l);
        if (e.getID() == MouseEvent.MOUSE_CLICKED) {
        System.out.println("Mouse click on layer: " + e.getPoint());
        }
    }
    }

    private class CustomCanvas extends Canvas implements MouseListener {

    @Override
    public void mouseClicked(MouseEvent e) {
        System.out.println("Mouse click on canvas: " + e.getPoint());
    }

    @Override
    public void mousePressed(MouseEvent e) {

    }

    @Override
    public void mouseReleased(MouseEvent e) {

    }

    @Override
    public void mouseEntered(MouseEvent e) {

    }

    @Override
    public void mouseExited(MouseEvent e) {

    }
    }
}

我搜索了一些开发人员尝试做我正在做的事情的例子，我发现的最佳答案是 this thread 上的最后一篇文章之一。 。基本上，建议是在 LayerUI 的 eventDispatched 方法中使用 InputEvent。在我的示例中，我尝试这样做(当 blockInput 标志设置为 true 时)，但它不会阻止输入进入 Canvas - 仍然打印 “Mouse clicked on canvas”... 消息。但是，“鼠标单击图层”... 不会打印，因此使用事件似乎只会阻止事件在 JLayer 内处理，但我需要它们不要进入 Canvas。作为一次孤注一掷的尝试，我还尝试在 processMouseEvent 中使用 MouseEvent，但没有成功。

我担心这个问题可能是因为 Canvas 是一个 AWT 组件，而不是一个轻量级的 Swing 组件。不幸的是，对于我正在编写的应用程序来说，它必须是一个 AWT Canvas。

有没有人设法从由 JLayer 装饰的重量级组件中获取 block 输入事件？

Answer 1

您的图层似乎可以与 JComponent 配合使用，例如 JPanel。另请参阅Mixing Heavyweight and Lightweight Components和How to Decorate Components with the JLayer Class .

import java.awt.AWTEvent;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.InputEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLayer;
import javax.swing.JPanel;
import javax.swing.plaf.LayerUI;

public class MyWindow extends JFrame {

    private boolean blockInput = true;
    private CustomPanel panel = new CustomPanel();

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> {
            new MyWindow().setVisible(true);
        });

    }

    public MyWindow() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        LayerUI<JPanel> layerUI = new CanvasLayerUI();
        JLayer<JPanel> canvasLayer = new JLayer<>(panel, layerUI);
        add(canvasLayer);
        pack();
        setLocationRelativeTo(null);
    }

    private class CanvasLayerUI extends LayerUI<JPanel> {

        @Override
        public void eventDispatched(AWTEvent e, JLayer<? extends JPanel> l) {
            if (blockInput) {
                if (e instanceof InputEvent) {
                    ((InputEvent) e).consume();
                }
            } else {
                super.eventDispatched(e, l);
            }
        }

        @Override
        public void installUI(JComponent c) {
            super.installUI(c);
            if (c instanceof JLayer) {
                JLayer<?> layer = (JLayer<?>) c;
                layer.setLayerEventMask(AWTEvent.MOUSE_EVENT_MASK);
            }
        }

        @Override
        protected void processMouseEvent(MouseEvent e, JLayer<? extends JPanel> l) {
            super.processMouseEvent(e, l);
            if (e.getID() == MouseEvent.MOUSE_CLICKED) {
                System.out.println("Mouse click on layer: " + e.getPoint());
            }
        }
    }

    private class CustomPanel extends JPanel {

        public CustomPanel() {
            this.addMouseListener(new MouseAdapter() {
                @Override
                public void mouseClicked(MouseEvent e) {
                    System.out.println("Mouse click on canvas: " + e.getPoint());
                }
            });
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(640, 480);
        }
    }
}