Java：当从另一个类引用时，为我的框架定义的绘制方法不会调用 repaint()

Question

我试图从另一个类调用这个构造函数，但是当我创建新线程时，它不会调用重绘。如果我只是从类中的 main 方法调用 run() 方法，它会完全按预期工作。似乎我的 repaint() 方法没有从其他类中调用。我担心我的其他班级还在做计算，但即使把它放在一个线程中，我也没有运气。

代码：

public class MakeTransparent implements Runnable{
private int i;
private static int dollars;
private float transparency;

public MakeTransparent(int dollars){

    this.setDollars(dollars);
    this.transparency = 1;
    this.i = 300;
}
@Override
public void run() {
    JFrame frame = new JFrame("Tiddlybiscuits"){
        private static final long serialVersionUID = 1L;

        public void paint(Graphics arg0) {
            Graphics2D g2 = (Graphics2D)arg0;
            super.paint(g2);
            g2.setColor(getBackground());
            g2.fillRect(0, 0, this.getWidth(),this.getHeight());
            g2.setColor(Color.CYAN);
            g2.setFont(g2.getFont().deriveFont(50, 200F));
            //System.out.println(arg0.getFontMetrics());
            String string = "+$";
            Composite c = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, getTransparency());
            g2.setComposite(c);
            g2.drawString(string + getDollars(), 30, getI());
            try {Thread.sleep(40);} catch (InterruptedException e) {}
            setI(getI()-5);
            setTransparency(getTransparency()-.03f);
            repaint();
        }
    };
    frame.setSize(500,500);
    frame.setLocationRelativeTo(null);
    frame.setUndecorated(true);
    frame.setBackground(new Color(1,55,134,0));

    frame.setLayout(null);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    try { Thread.sleep(1400); } catch (InterruptedException e) {    }
    frame.dispose();
}

Answer 1

• 不要在事件调度线程的上下文中调用Thread.sleep EVER
• 不要在paint方法中调用任何可能导致repaint发生的方法，这将导致无限更新循环，最终会消耗你的CPU
• 避免覆盖paint 等顶级容器，例如JFrame，除了没有被双缓冲之外，大多数窗口都包含其他组件（JRootPane、contentPane、glassPane）所有这些都会干扰你的身份试着画画
• Swing 是单线程框架，不是线程安全的。这意味着您永远不应该在事件调度线程的上下文中执行任何长时间运行或阻塞的操作，也不应该从事件调度线程外部创建或修改任何 UI 组件。
• 只有一个 EDT，所有 UI 代码都会在其中运行。绘画之类的事情总是在 EDT 内自动执行。

看看：

• Painting in AWT and Swing
• Performing Custom Painting
• Concurrency in Swing
• Worker Threads and SwingWorker
• How to use Swing Timers

有关如何在框架要求中工作的更多详细信息和想法

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Composite;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
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();
                }

                TestPane tp = new TestPane();
                Timer timer = new Timer(40, new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        float t = tp.getTransparancy() - 0.03f;
                        if (t < 0) {
                            t = 0;
                            ((Timer)e.getSource()).stop();
                        }
                        int i = tp.getI();

                        tp.setI(i - 1);
                        System.out.println(t);
                        tp.setTransparancy(t);
                    }
                });

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

    public class TestPane extends JPanel {

        private float transparancy = 1f;
        private int i = 200;
        private int dollars;

        public TestPane() {
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 200);
        }

        public void setTransparancy(float value) {
            if (transparancy != value) {
                float old = transparancy;
                this.transparancy = value;
                firePropertyChange("transparancy", old, transparancy);
                repaint();
            }
        }

        public float getTransparancy() {
            return transparancy;
        }

        public int getDollars() {
            return dollars;
        }

        public int getI() {
            return i;
        }

        public void setI(int value) {
            if (i != value) {
                float old = i;
                this.i = value;
                firePropertyChange("i", old, i);
                repaint();
            }
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(getBackground());
            g2d.fillRect(0, 0, this.getWidth(), this.getHeight());
            g2d.setColor(Color.CYAN);
            g2d.setFont(g2d.getFont().deriveFont(50, 200F));
            //System.out.println(arg0.getFontMetrics());
            String string = "+$";
            Composite c = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, getTransparancy());
            g2d.setComposite(c);
            g2d.drawString(string + getDollars(), 30, getI());
            g2d.dispose();
        }

    }

}