Question

java 的一段代码，运行后控件不显示，执行最小化或者最大化操作后控件才显示,求解！！谢谢！！

package com.lzw;
import java.awt.*;
import javax.swing.*;
public class UseCase1 extends JFrame{
private JComboBox comboBox;
public static void main(String[] args) {
new UseCase1();
}
public UseCase1() {
super();
setVisible(true);
setSize(200,150);
setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
comboBox = new JComboBox();
comboBox.addItem("红");
comboBox.addItem("黄");
comboBox.addItem("蓝");
comboBox.addItem("黑");
getContentPane().add(comboBox, BorderLayout.NORTH);
final JPanel panel = new JPanel();
getContentPane().add(panel, BorderLayout.CENTER);
final JCheckBox checkBox = new JCheckBox();
checkBox.setText("男");
panel.add(checkBox);
final JCheckBox checkBox_1 = new JCheckBox();
checkBox_1.setText("女");
panel.add(checkBox_1);
final JPanel panel_1 = new JPanel();
getContentPane().add(panel_1, BorderLayout.SOUTH);
final JButton okButton = new JButton();
okButton.setText("确定");
panel_1.add(okButton);
final JButton button_1 = new JButton();
button_1.setText("取消");
panel_1.add(button_1);
}
}

Answer 1

把对JFrame类的设置移动到构造函数的末尾就行了。
具体的完整程序如下：（注意注释）
package com.lzw;
import java.awt.*;
import javax.swing.*;
public class UseCase1 extends JFrame{
private JComboBox comboBox;
public static void main(String[] args) {
new UseCase1();
}
public UseCase1() {
super();

comboBox = new JComboBox();
comboBox.addItem("红");
comboBox.addItem("黄");
comboBox.addItem("蓝");
comboBox.addItem("黑");
getContentPane().add(comboBox, BorderLayout.NORTH);
final JPanel panel = new JPanel();
getContentPane().add(panel, BorderLayout.CENTER);
final JCheckBox checkBox = new JCheckBox();
checkBox.setText("男");
panel.add(checkBox);
final JCheckBox checkBox_1 = new JCheckBox();
checkBox_1.setText("女");
panel.add(checkBox_1);
final JPanel panel_1 = new JPanel();
getContentPane().add(panel_1, BorderLayout.SOUTH);
final JButton okButton = new JButton();
okButton.setText("确定");
panel_1.add(okButton);
final JButton button_1 = new JButton();
button_1.setText("取消");
panel_1.add(button_1);

setVisible(true); //把这句移动到这里
setSize(200,150); //把这句移动到这里
setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); //把这句移动到这里
}
}

Answer 2

三种解决办法
1，this.setLayout(new BorderLayout());手动设置布局管理器
2，this.setResizable(false);
3，pack();