JAVA swing gui window 在重绘方法运行后变得不和谐

Question

我开始学习 Java Swing。我试图创建一个 GUI，其中有 2 个按钮，底部的 changeColor 和右侧的 changeLabel。它在右侧和中心有一个标签 JPanel，显示渐变色的椭圆形。

当我点击 changeLabel 时，它工作正常并更改了左侧的标签。但是当我点击 changeColor 时，出现了一个新的椭圆形，整个布局被打破，一些新的面板叠加在一起。我正在关注一本书，其中给出了相同的东西，但是它在 paintComponent 方法中使用了随机颜色生成，我从这里学到的，这不是一件好事。该方法工作正常，但我试图避免这种情况并制作一个单独的方法。但这不起作用。

图形界面 class:

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

public class TwoButtons {
    public JFrame frame;
    private JLabel label;
    private MyDrawPanel panel;
    private boolean clicked = false;

    public static void main(String[] args) {
        TwoButtons gui = new TwoButtons();
        gui.go();
    }

    public void go() {
        frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JButton labelButton = new JButton("Change Label");
        labelButton.addActionListener(new LabelListener());

        JButton colorButton = new JButton("Change color");
        colorButton.addActionListener(new ColorListener());

        label = new JLabel("I'm a label");
        panel = new MyDrawPanel();
        frame.getContentPane().add(BorderLayout.SOUTH, colorButton);
        frame.getContentPane().add(BorderLayout.CENTER, panel);
        frame.getContentPane().add(BorderLayout.EAST, labelButton);
        frame.getContentPane().add(BorderLayout.WEST, label);

        frame.setSize(300, 300);
        frame.setVisible(true);
    }

    class LabelListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (!clicked) {
                label.setText("Ouch!! (Click again to revert)");
                clicked = true;
            } else {
                clicked = false;
                label.setText("Change Label");
            }
        }
    }

    class ColorListener implements ActionListener {
       @Override//
       public void actionPerformed(ActionEvent e) {
           //frame.repaint();
               panel.changeColors();
    }
}
}

填色class:

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

public class MyDrawPanel  extends  JPanel{
    private Color startColor,endColor;
    public MyDrawPanel(){
        this.changeColors();
    }
    public void  paintComponent(Graphics g){
        Graphics2D g2D=(Graphics2D)g;
        GradientPaint gradient=new GradientPaint(70,70,startColor,150,150,endColor);
        g2D.setPaint(gradient);
        g2D.fillOval(70,70,100,100);
    }
    public void changeColors(){
        int red = (int) (Math.random() * 255);
        int green = (int) (Math.random() * 255);
        int blue = (int) (Math.random() * 255);
        startColor = new Color(red, green, blue);
        red = (int) (Math.random() * 255);
        green = (int) (Math.random() * 255);
        blue = (int) (Math.random() * 255);
        endColor = new Color(red, green, blue);
        this.repaint();

    }

}

点击前改变颜色

点击后更改颜色

Answer 1

为了避免渲染瑕疵：

public void paintComponent(Graphics g){ ..

应该是：

public void paintComponent(Graphics g){ 
    super.paintComponent(g); ..

调用super方法，会自动重新绘制背景、边框等，从而擦除之前的绘制。

JAVA swing gui window 在重绘方法运行后变得不和谐

JAVA swing gui window gets jarred after repaint method is run

java

swing

paintcomponent

JAVA swing gui window 在重绘方法 运行 后变得不和谐

JAVA swing gui window gets jarred after repaint method is run

java

swing

paintcomponent

JAVA swing gui window 在重绘方法运行后变得不和谐