通过JLayer和LayerUI缩放JLayeredPane

Question

在这个问题上，有人建议在Swing应用程序中实现缩放的最佳方法是通过JLayerJava
7附带的装饰器。

我一直在关注Oracle教程，并且认为做到这一点的最佳方法是创建自己的ZoomUI扩展LayerUI。到目前为止，我的想法是该类将具有一个zoom在绘制实际组件之前应用的成员变量。

然后，稍后我可以使用相同的类来捕获鼠标事件，并将其分配到未缩放的坐标。

我在第一步时遇到了一些麻烦，无法理解为什么g2.scale(zoom, zoom)呼叫在下面的SSCCE中没有效果。

import javax.swing.*;
import javax.swing.plaf.LayerUI;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;

public class Demo {


    public static void main(String args[]) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

                final JLayeredPane panel = new JLayeredPane();
                final ZoomUI layerUI = new ZoomUI();
                final JLayer<JComponent> jLayer = new JLayer<JComponent>(panel, layerUI);

                Button zoomIn = new Button("Zoom In");
                zoomIn.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                       layerUI.zoom += 0.1;
                       jLayer.repaint();
                    }
                });
                zoomIn.setBounds(0,0,100,50);
                panel.add(zoomIn);

                Button zoomOut = new Button("Zoom Out");
                zoomOut.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                        layerUI.zoom -= 0.1;
                        jLayer.repaint();
                    }
                });
                zoomOut.setBounds(100,0,100,50);
                panel.add(zoomOut);

                frame.setPreferredSize(new Dimension(400,200));
                frame.add(jLayer);
                frame.pack();
                frame.setVisible(true);
            }
        });
    }

    private static class ZoomUI extends LayerUI<JComponent> {
        public int zoom = 1.5; // Changing this value seems to have no effect
        @Override
        public void paint(Graphics g, JComponent c) {
            Graphics2D g2 = (Graphics2D) g.create();
            g2.scale(zoom, zoom);
            super.paint(g2, c);
            g2.dispose();
        }

        @Override
        public void installUI(JComponent c) {
            super.installUI(c);
            JLayer jlayer = (JLayer)c;
            jlayer.setLayerEventMask(
                    AWTEvent.MOUSE_EVENT_MASK | AWTEvent.ACTION_EVENT_MASK |
                            AWTEvent.MOUSE_MOTION_EVENT_MASK
            );
        }

        @Override
        public void uninstallUI(JComponent c) {
            JLayer jlayer = (JLayer)c;
            jlayer.setLayerEventMask(0);
            super.uninstallUI(c);
        }
    }
}

在此示例中，我期望单击和缩放以正确响应鼠标事件时，放大/缩小按钮的大小会增加。不必单击它们曾经驻留的位置即可触发事件。

可悲的是，我什至无法通过更改注释行来放大它们，因此，我非常感谢您的帮助！

Answer 1

您的直接问题是，您正在混合重量级/ AWT组件和重量轻/ Swing组件…

Button 是本地组件，这意味着它的绘画超出了Swing的控制范围，因此不受其影响。

而是使用JButton代替。

public class TestJLayerZoom {

    public static void main(String args[]) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

                final JPanel panel = new JPanel();
                final ZoomUI layerUI = new ZoomUI();
                final JLayer<JComponent> jLayer = new JLayer<JComponent>(panel, layerUI);

                JButton zoomIn = new JButton("Zoom In");
                zoomIn.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                        layerUI.zoom += 0.1;
                        jLayer.repaint();
                    }
                });
                panel.add(zoomIn);

                JButton zoomOut = new JButton("Zoom Out");
                zoomOut.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                        layerUI.zoom -= 0.1;
                        jLayer.repaint();
                    }
                });
                panel.add(zoomOut);

                frame.setPreferredSize(new Dimension(400, 200));
                frame.add(jLayer);
                frame.pack();
                frame.setVisible(true);
            }
        });
    }

    private static class ZoomUI extends LayerUI<JComponent> {

        public double zoom = 2; // Changing this value seems to have no effect

        @Override
        public void paint(Graphics g, JComponent c) {
            Graphics2D g2 = (Graphics2D) g.create();
            g2.scale(zoom, zoom);
            super.paint(g2, c);
            g2.dispose();
        }

        @Override
        public void installUI(JComponent c) {
            super.installUI(c);
            JLayer jlayer = (JLayer) c;
            jlayer.setLayerEventMask(
                    AWTEvent.MOUSE_EVENT_MASK | AWTEvent.ACTION_EVENT_MASK
                    | AWTEvent.MOUSE_MOTION_EVENT_MASK
            );
        }

        @Override
        public void uninstallUI(JComponent c) {
            JLayer jlayer = (JLayer) c;
            jlayer.setLayerEventMask(0);
            super.uninstallUI(c);
        }
    }
}

您的下一个问题将是研究如何转换鼠标事件;）