Question

Java 小程序，label 放到 panel 里面，panel 放到 frame 里面，为什么 label 没能显示出来呢？

/**
* Filename: tsForJPanel.java
* @author: Amitayus
* Created : 2013/10/31 19:08:49
*/
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Toolkit;

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

public class TestFor {
public static void main(String[] args) {
JFrame jFrame = new JFrame("test for jpanel");
jFrame.setResizable(true);
jFrame.setLayout(null);
Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
jFrame.setBounds(((int)dimension.getWidth() - 400) / 2, ((int)dimension.getHeight() - 300) / 2, 400, 300);
jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JPanel panel = new JPanel();
panel.setLayout(null);
panel.setPreferredSize(new Dimension(200,150));
panel.setBackground(Color.CYAN);

JLabel label1 = new JLabel("姓名");
label1.setBounds(10, 10, 100, 30);
panel.add(label1);

jFrame.add(panel);

label1.setVisible(true);
jFrame.setVisible(true);
}
}

Answer 1

//panel.setPreferredSize(new Dimension(200, 150));
注释掉上面这句，加一个尺寸，就可以了
panel.setBounds(0,0,200,150);

Answer 2

jFrame.setLayout(new FlowLayout());里面不应该是null，望采纳，谢谢