Java：为我的框架定义的绘制方法在从另一个 class 引用时不会调用 repaint()

Question

我试图从另一个 class 调用此构造函数，但是当我创建新线程时，它从来没有调用重绘。如果我只是从 class 中的 main 方法调用运行() 方法，它会完全按预期工作。似乎我的 repaint() 方法没有被另一个 class 调用。我担心我的另一个class还在计算，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

永远不要从事件调度线程的上下文中调用 Thread.sleep
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 顶级容器，如 JFrame，除了没有双缓冲，大多数 windows 包含其他组件（JRootPane、contentPane, glassPane) 所有这些都会干扰您尝试绘制的内容
Swing 是单线程框架，不是线程安全的。这意味着你不应该在事件调度线程的上下文中执行任何长时间的运行或阻塞操作，你也不应该在事件调度线程之外创建或修改任何 UI 组件。
只有一个 EDT，所有 UI 代码都将运行在其中。像绘画这样的事情总是在 EDT 中自动执行。

看看：

有关如何在框架要求内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();
        }

    }

}

Java：为我的框架定义的绘制方法在从另一个 class 引用时不会调用 repaint()

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