为什么我的代码执行了两次paintComponent(Graphics page)?

why is my code executing paintComponent(Graphics page) twice?(为什么我的代码执行了两次paintComponent(Graphics page)?)

问题描述

这让我很紧张，这对我来说可能有些愚蠢，但我不明白为什么我的paintComponent 被调用了两次，如果你运行我的代码，它会输出 REPEAT?重复?两次，我不希望它这样做.. 那么它为什么会这样做，我该如何解决呢?

This is getting on my nerves and it probably something silly on my part but I can't figure out why my paintComponent is being called twice, if you run my code it outputs REPEAT? REPEAT? twice, I don't want it to do that.. So why does it do it and how can I fix it?

import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.*;

public class Main extends JPanel {


    public Main()
    {      
     /*code here*/
    }

    public void paintComponent(Graphics page)
    {
     clear(page);

        /*code here*/

        System.out.println("REpEAT?"); 

    }

    protected void clear(Graphics page) {
        super.paintComponent(page);
      }

    public static void main (String[] args)
    {
        JFrame frame = new JFrame ("Circles");
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 200);
        frame.getContentPane().add(new Main());
        frame.setVisible(true);

    }



}

推荐答案

我也打印了两次.

但是，我认为这不必担心.Swing 决定何时需要重新粉刷.例如，如果您调整窗口大小或最小化/最大化，Swing 将重新绘制.它可能取决于您运行的操作系统/硬件.

However, I don't think it is cause for concern. Swing decides when things need to be repainted. For example, if you resize a window or minimise/maximise, Swing will repaint. It might be dependent on the OS/hardware you are running on.

您应该编写代码，使其足够健壮以处理对 repaint 的多次调用.

You should write your code so that it is robust enough to handle multiple calls to repaint.

请也查看这个 SO 问题:paintComponent 正在执行两次

Please see this SO question too: paintComponent is executing twice

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