java从JPanel中动态删除组件

Question

下面是一段可运行的代码，解释了这个问题-

我可以删除s1和s2，但不能删除s3
这似乎与MigLayout无关（我碰巧正在使用它），因为我看到默认布局也有相同的行为

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

import net.miginfocom.swing.MigLayout;

public class MyFrame2 extends JFrame {
    private JPanel main;
    private JPanel s1;
    private JPanel s2;
    private JPanel s3;

    public static void main(String[] args) throws InterruptedException {
        MyFrame2 f = new MyFrame2();
        f.setVisible(true);
        Thread.sleep(2000); //you can see all three panels for two seconds

        f.main.remove(f.s1);
        f.main.validate();
        Thread.sleep(2000);
        f.main.remove(f.s2);
        f.main.validate();
        Thread.sleep(2000);
        f.main.remove(f.s3);
        f.main.validate();
    }

    public MyFrame2() {
        main = new JPanel();

        main.setLayout(new MigLayout());

        main.add(new JLabel("Why does s3 not disappear?"),"w 200, h 100, wrap");

        s1 = new JPanel();
        s1.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.GRAY,1),"s1"));
        main.add(s1,"w 90%, h 300, wrap");

        s2 = new JPanel();
        s2.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.GRAY,1),"s2"));
        main.add(s2,"w 90%, h 300, wrap");

        s3 = new JPanel();
        s3.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.GRAY,1),"s3"));
        main.add(s3,"w 90%, h 300, wrap");

        getContentPane().setLayout(new BorderLayout());
        getContentPane().add(main, BorderLayout.CENTER);

        setSize(new Dimension(800, 600));

    }
}

Answer 1

在最后一个f.validate()之后的末尾调用：

f.repaint(50L);

因为最后一次验证不会更改布局

Answer 2

首先，Swing GUI对象应该只在event dispatch thread上构造和操作，但不能在EDT上睡觉。而是使用^{}来标记时间，如图here所示