放大和缩小面板但滚动条不起作用

Question

我创建了一个具有放大和缩小功能的面板，但滚动条不起作用，我的意思是当我放大时我无法滚动查看整个面板。
这是我的代码：

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JScrollPane;
import java.awt.Dimension;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

@SuppressWarnings("serial")
public class PanelWithZoom extends JPanel{

    private JButton btnZoomIn;
    private JButton btnZoomOut;
    private double scale = 1;
    private JPanel innerPanel;
    private JPanel outerPanel;
    public PanelWithZoom() {
        setLayout(new BorderLayout(0, 0));

        JPanel panel = new JPanel();
        add(panel, BorderLayout.NORTH);

        btnZoomIn = new JButton("zoom in");
        btnZoomIn.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                scale = scale + 0.1;
                outerPanel.repaint();
                outerPanel.revalidate();
            }
        });
        panel.add(btnZoomIn);

        btnZoomOut = new JButton("zoom out");
        btnZoomOut.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                scale = scale - 0.1;
                outerPanel.repaint();
                outerPanel.revalidate();
            }
        });
        panel.add(btnZoomOut);

        JPanel panel_1 = new JPanel();
        add(panel_1, BorderLayout.WEST);

        JPanel panel_2 = new JPanel();
        add(panel_2, BorderLayout.SOUTH);

        JPanel panel_3 = new JPanel();
        add(panel_3, BorderLayout.EAST);

        outerPanel = new JPanel(){
            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);

                Graphics2D g2 = (Graphics2D) g;             
                int w = (int) getWidth();
                int h = (int) getHeight();
                // Translate used to make sure scale is centered
                g2.translate(w/2, h/2);
                g2.scale(scale, scale);
                g2.translate(-w/2, -h/2);
            }


        };
        JScrollPane scroll = new JScrollPane(outerPanel);
        add(scroll, BorderLayout.CENTER);

        innerPanel = new JPanel(){
            @Override
            protected void paintComponent(Graphics g) {
                Graphics2D g2 = (Graphics2D) g;             
                g2.setColor(Color.white);
                g2.fillRect(0, 0, getWidth(), getHeight());
                g2.setColor(Color.black);
                g2.drawString("String for test", 10, 50);
                g2.drawRect(0, 0, getWidth()-1, getHeight()-1);
                setPreferredSize(new Dimension(595, 842));
            }

        };

        outerPanel.add(innerPanel);
    }


    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setContentPane(new PanelWithZoom());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
        frame.setVisible(true);
    }

}

你可以测试它以理解我的意思。

Answer 1

覆盖组件的getPreferredSize方法，根据组件的scale和原始大小返回组件的大小。

因为您想对子组件应用缩放，您可能希望覆盖paint而不是paintComponent

outerPanel = new JPanel(){
    @Override
    public void paint(Graphics g) {
        Graphics2D g2 = (Graphics2D) g.create();             
        g2.scale(scale, scale);
        super.paint(g);
        g2.dispose()
    }
}    

但是，Swing组件可以独立于其父容器进行绘制，这意味着在绘制子组件时可能不会调用paint方法...

问题在于，它不会缩放鼠标事件（或许多其他属性）。

随着问题列表越来越多，更好的解决方案是使用像JXLayer这样的东西，如演示here

附注：

• 使用Graphics#create复制Graphics上下文和Graphics#dispose的属性，在处理翻译/转换/呈现提示和一堆其他属性时更安全，如对副本的任何更改都不会影响原始
• 不要在任何可能直接或间接导致重绘事件被触发的绘制方法中调用任何方法，你最终会陷入一个令人讨厌的永不停止的循环，最终会消耗你的CPU

图形#create和#Dispose示例......

outerPanel = new JPanel(){
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        Graphics2D g2 = (Graphics2D) g.create();             
        int w = (int) getWidth();
        int h = (int) getHeight();
        // Translate used to make sure scale is centered
        g2.translate(w/2, h/2);
        g2.scale(scale, scale);
        g2.translate(-w/2, -h/2);
        g2.dispose();
    }
}