Java中GUI编程的怪异问题

Question

下面是我的代码：

package javaapplication13;

import java.awt.*;
import javax.swing.*;

public class JavaApplication13 {
    public static void main(String[] args) {
        ButtonFrame bf = new ButtonFrame();
    }
}

class ButtonFrame extends JFrame {
    public ButtonFrame() {
        JButton b1 = new JButton("1. Dugme");
        JButton b2 = new JButton("2. Dugme");
        JLabel l1 = new JLabel();
        JCheckBox c1 = new JCheckBox("Prvo dugme");
        JCheckBox c2 = new JCheckBox("Drugo dugme");
        Container cp = getContentPane();
        setTitle("Dugme");
        setSize(400,400);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
        this.add(b1);
        this.add(b2);
        this.add(c1);
        this.add(c2);
        this.add(l1);
        b1.setBounds(20, 30, 90, 20);
        b2.setBounds(20,70,90,20);
        l1.setBounds(70,120,90,20);
        c1.setBounds(120,30,120,20);
        c2.setBounds(120,70,120,20);

        l1.setText("");
    }
}

Answer 1

当我用JDK17在我的Windows10计算机上复制和运行您的代码时，我没有看到您声称得到的闪烁。然而，当我更改代码并在添加按钮和复选框之前将标签添加到框架中时（正如您在问题中所述），我确实看到了“闪烁”。

虽然您已经接受@Antoniossss的回答，但不建议不使用布局管理器。请参考以下摘录自没有布局管理器的情况下

尽管没有布局管理器也是可能的，但如果可能的话，您应该使用布局管理器。

import java.awt.Container;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JComponent;
import javax.swing.JFrame;

public class BtnFrame {
    private void createAndDisplayGui() {
        JFrame frame = new JFrame("Dugme");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new GridBagLayout());
        createForm(frame.getContentPane());
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private void createForm(Container contentPane) {
        if (contentPane instanceof JComponent) {
            JComponent jCmpt = (JComponent) contentPane;
            jCmpt.setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
        }
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.anchor = GridBagConstraints.LINE_START;
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.insets.bottom = 5;
        gbc.insets.left = 5;
        gbc.insets.right = 5;
        gbc.insets.top = 5;
        JButton b1 = new JButton("1. Dugme");
        contentPane.add(b1, gbc);
        gbc.gridx = 1;
        JCheckBox c1 = new JCheckBox("Prvo dugme");
        contentPane.add(c1, gbc);
        gbc.gridx = 0;
        gbc.gridy = 1;
        JButton b2 = new JButton("2. Dugme");
        contentPane.add(b2, gbc);
        gbc.gridx = 1;
        JCheckBox c2 = new JCheckBox("Drugo dugme");
        contentPane.add(c2, gbc);
        gbc.gridx = 0;
        gbc.gridy = 2;
        gbc.anchor = GridBagConstraints.CENTER;
        JLabel l1 = new JLabel("label");
        contentPane.add(l1, gbc);
    }

    public static void main(String[] args) {
        final BtnFrame gui = new BtnFrame();
        EventQueue.invokeLater(() -> gui.createAndDisplayGui());
    }
}

import java.awt.Container;

import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;

public class ButtonFrame extends JFrame {
    public ButtonFrame(){
        
        JButton b1 = new JButton("1. Dugme");
        JButton b2 = new JButton("2. Dugme");
        JLabel l1 = new JLabel();
        JCheckBox c1 = new JCheckBox("Prvo dugme");
        JCheckBox c2 = new JCheckBox("Drugo dugme");
        Container cp = getContentPane();
        cp.setLayout(null); // Added this line.
        setTitle("Dugme");
        setSize(400,400);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
        this.add(l1);
        this.add(b1);
        this.add(b2);
        this.add(c1);
        this.add(c2);
//        this.add(l1);
        b1.setBounds(20, 30, 90, 20);
        b2.setBounds(20,70,90,20);
        l1.setBounds(70,120,90,20);
        c1.setBounds(120,30,120,20);
        c2.setBounds(120,70,120,20);
        
        l1.setText("label");
    }

    public static void main(String[] args) {
        ButtonFrame bf = new ButtonFrame();
    }
}