java - 最简单的 Gui 测试 Java 重绘

Question

这是一个简单的问题，也许我只是不明白我正在阅读的教程。但我已经坚持了一段时间了。我的程序很简单，除了“hello world”之外。我想做的是:当用户单击按钮时，“O”向右移动。很简单，但是我该把 repaint() 放在哪里呢？我需要添加一些东西。repaint();重新绘制屏幕还是单独绘制屏幕？嵌套类问题？ T_T 这让我很痛苦，似乎没有人遇到这个我无法理解的问题。提前致谢。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class GuiTest {

    static int x = 20;

    private static class moveTest extends JPanel {

        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawString("O", x, 30);
        }
    }

    private static class ButtonHandler implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            x += 1;
        }
    }

    public static void main(String[] args) {
        moveTest displayPanel = new moveTest();
        JButton okButton = new JButton("move");
        ButtonHandler listener = new ButtonHandler();
        okButton.addActionListener(listener);

        JPanel content = new JPanel();
        content.setLayout(new BorderLayout());
        content.add(displayPanel, BorderLayout.CENTER);
        content.add(okButton, BorderLayout.SOUTH);

        JFrame window = new JFrame("GUI Test");
        window.setContentPane(content);
        window.setSize(250, 100);
        window.setLocation(100, 100);
        window.setVisible(true);
    }
}

Answer 1

考虑让您的 MoveTest 面板导出 Action供 GuiTest 按钮使用。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class GuiTest {

    private static class MoveTest extends JPanel {

        private int x = 20;
        private int y = 20;

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawString("<O>", x, y);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(256, 128);
        }

        public Action getAction() {
            return new ButtonHandler("Move");
        }

        private class ButtonHandler extends AbstractAction {

            public ButtonHandler(String name) {
                super(name);
            }

            @Override
            public void actionPerformed(ActionEvent e) {
                x += 2;
                y += 1;
                repaint();
            }
        }
    }

    public static void main(String[] args) {
        MoveTest displayPanel = new MoveTest();
        JButton moveButton = new JButton(displayPanel.getAction());

        JFrame window = new JFrame("GUI Test");
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.add(displayPanel);
        window.add(moveButton, BorderLayout.SOUTH);
        window.pack();
        window.setLocationByPlatform(true);
        window.setVisible(true);
    }
}