为什么仍要重新粉刷此JPanel？

Question

我有一个自定义的JLayeredPane和两个自定义的子JPanel 。 我在Thread的while循环中重新绘制了所有内容。 我已经用过RepaintManager.currentManager(backPanel).markCompletelyClean(backPanel); 停止重新绘制backPanel JPanel 。 为了不浪费系统资源。 但是，这不起作用。 正如我们在paintComponent方法中看到的那样，如果运行并编译下面的代码，您将看到在输出中从系统中System.out.println("Reccursion")方法调用中递归地重复了语句“ Reccursion”。 paintComponent方法。

为什么当我使用RepaintManager.currentManager(backPanel).markCompletelyClean(backPanel); ，为什么仍要重新绘制backPanel JPanel以及为什么仍然要调用System.out.println("Reccursion")方法RepaintManager.currentManager(backPanel).markCompletelyClean(backPanel); 。

import javax.swing.*;

import java.awt.*;
import java.awt.event.*;

public class Main extends JLayeredPane {
    static JFrame frame;
    static Main main;
    static Dimension screenSize;
    public Main() {     
        JPanel backPanel = new BackPanel();
        JPanel frontPanel = new FrontPanel();
        add(backPanel, new Integer(7));
        add(frontPanel, new Integer(8));

        new Thread(() -> {
            while (true){
                repaint();
            }
        }).start();

        RepaintManager.currentManager(backPanel).markCompletelyClean(backPanel);

    }

    public static void main(String[] args) {
        screenSize = Toolkit.getDefaultToolkit().getScreenSize();

        frame = new JFrame("Game"); // Just use the constructor

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        main = new Main();
        frame.add(main, BorderLayout.CENTER);

        frame.pack();
        frame.setSize(screenSize);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);



    }
    public class BackPanel extends JPanel{
        public boolean drawn = false;
        public BackPanel(){
            setVisible(true);
            setOpaque(false);
            setSize(screenSize);
            JLabel test1 = new JLabel("Test1");
            JLabel test2 = new JLabel("Test2");
            add(test1);
            add(test2);
        }
        @Override
        public void paintComponent(Graphics g){
            super.paintComponent(g);
            g.setColor(Color.red);
            g.fillRect(0, 0, screenSize.width, 200);
            System.out.print("Reccursion");
        }
    }
    public class FrontPanel extends JPanel{

        public FrontPanel(){
            setVisible(true);
            setOpaque(false);
            setSize(screenSize);
            JLabel test = new JLabel("Test");
            add(test);
        }
        @Override
        public void paintComponent(Graphics g){
            super.paintComponent(g);
            g.setColor(Color.blue);
            g.fillRect(0+screenSize.width/2, 0, screenSize.width/4, 300);
        }
    }
}

Answer 1

方法“ paintComponent”经常被调用，并且没有您的“权限”（这也让我很难受...）。您不能对此做任何事情，只是不要每次都用这种方法生成新数据或外观可能会经常变化。 祝好运

https://books.google.fr/books?id=KXz6AQAAQBAJ&pg=PA211&lpg=PA211&dq=paintcomponent+called+repeatedly&source=bl&ots=AEql59yy51&sig=Ezny1GptXRthd1e0tuQFdM5peoo&hl=fr&sa=X&ved=0ahUKEwjun4j6rJHOAhWK2xoKHYaPCEQ4ChDoAQgkMAE#v=onepage&q=paintcomponent%20called%20repeatedly&f=false