Question

我正在尝试制作一个背景随时间变化缓慢的JFrame。这是我的代码：

public class RainbowWindow extends Applet implements ActionListener {

    private static final long serialVersionUID = 1L;

    public void paint(Graphics g) {
        Timer timer = new Timer(1000, this);
        timer.start();
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        Color color = new Color(((int) Math.random()), ((int) Math.random()), ((int) Math.random()), 255);
        setBackground(color);

    }
}

但我得到的只是一个黑屏

Answer 1

Java Plugin support deprecated和Moving to a Plugin-Free Web
不要在Timer中创建paint，每次都需要绘制绘画，并且通常需要快速连续绘制。有关绘画如何在Swing

Painting in AWT and Swing

Performing Custom Painting

您应该避免覆盖paint和JFrame等顶级容器的Applet，它们不是双重缓冲的，它往往不会导致问题的结束，最好从一些开始一种组件并将其添加到您想要的任何容器中
JFrame！= Applet
Math.random返回0和1之间的值，Color期望0 - 255

例如

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            Timer timer = new Timer(1000, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    int red = (int)(Math.random() * 255);
                    int green = (int)(Math.random() * 255);
                    int blue = (int)(Math.random() * 255);
                    Color color = new Color(red, green, blue, 255);
                    setBackground(color);
                }
            });
            timer.start();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

    }
}

Answer 2

您应该延长JApplet（不是Applet），并添加一个组件来设置颜色，您不应该在Timer中开始paint并且，将浮点值转换为int不会在随机颜色生成中为您提供任何值。像，

public class RainbowWindow extends JApplet implements ActionListener {

    private static final long serialVersionUID = 1L;

    private JPanel panel = new JPanel();

    @Override
    public void actionPerformed(ActionEvent e) {
        Color color = new Color(((int) (Math.random() * 255)),
                ((int) (Math.random() * 255)),
                ((int) (Math.random() * 255)), 255);
        panel.setBackground(color);
    }

    public RainbowWindow() {
        Timer timer = new Timer(1000, this);
        timer.start();
        add(panel);
        setVisible(true);
    }
}

我测试了它，它每秒一次将背景颜色更改为新的随机颜色。

使用随机颜色更新Applet

2 个答案: