java SWING/GUI测试程序

//setVisible一定要放在所有组件之后//否则容易引起界面上组件不全等非正常现象//以下程序刚开始运行的界面没有显示复选框，//当改变窗口大小后，复选框才正常显示package snake;import javax.swing.*;public class Test{public static void main(String[] args)    {    JFrame jf=new JFrame("添加内容面板测试程序");    jf.setSize(500,500);    jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        JPanel contentPane=new JPanel();    jf.setContentPane(contentPane);     jf.setVisible(true);    JCheckBox jr1=new JCheckBox("羽毛球");    JCheckBox jr2=new JCheckBox("足球");    JCheckBox jr3=new JCheckBox("电脑书");    JCheckBox jr4=new JCheckBox("数学书");    JCheckBox jr5=new JCheckBox("电影");    JCheckBox jr6=new JCheckBox("录像");        contentPane.add(jr1);    contentPane.add(jr2);    contentPane.add(jr3);    contentPane.add(jr4);    contentPane.add(jr5);    contentPane.add(jr6);        } }

修改程序：将jf.setVisible(true);放在程序最后可正常显示。

//说明一个布局管理器只能用一次，不能多次使用package snake;import javax.swing.*;import java.awt.*;public class Test{public static void main(String[] args)    {    JFrame jf=new JFrame("测试程序");    jf.setSize(500,500);    jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    JPanel contentPane=new JPanel();    jf.setContentPane(contentPane);    JPanel pan1=new JPanel();    JPanel pan2=new JPanel();    JPanel pan3=new JPanel();    JPanel pan4=new JPanel();    JPanel pan5=new JPanel();    JButton b1=new JButton("生活");    JButton b2=new JButton("工作");    JButton b3=new JButton("睡觉");    JButton b4=new JButton("购物");    JButton b5=new JButton("饮食");    JButton b6=new JButton("6");    JButton b7=new JButton("7");    JButton b8=new JButton("8");    JButton b9=new JButton("9");    JButton b10=new JButton("10");    JButton b11=new JButton("11");    JButton b12=new JButton("12");    JButton b13=new JButton("13");    JButton b14=new JButton("14");    JButton b15=new JButton("15");    JButton b16=new JButton("16");    JButton b17=new JButton("17");    JButton b18=new JButton("18");    JButton b19=new JButton("19");    JButton b20=new JButton("20");    JButton b21=new JButton("21");    JButton b22=new JButton("22");    JButton b23=new JButton("23");    JButton b24=new JButton("24");    JButton b25=new JButton("25");    BorderLayout lay=new BorderLayout();    contentPane.setLayout(lay);        //第一次使用lay    contentPane.add(pan1,"North");    contentPane.add(pan2,"South");    contentPane.add(pan3,"East");    contentPane.add(pan4, "West");    contentPane.add(pan5,"Center");       pan1.setLayout(lay);    //若再次使用    pan2.setLayout(new BorderLayout());    pan3.setLayout(new BorderLayout());    pan4.setLayout(new BorderLayout());    pan5.setLayout(new BorderLayout());    pan1.add(b1,"North");    pan1.add(b2,"South");    pan1.add(b3,"East");    pan1.add(b4, "West");    pan1.add(b5,"Center");      pan2.add(b6,"North");    pan2.add(b7,"South");    pan2.add(b8,"East");    pan2.add(b9, "West");    pan2.add(b10,"Center");    pan3.add(b11,"North");    pan3.add(b12,"South");    pan3.add(b13,"East");    pan3.add(b14, "West");    pan3.add(b15,"Center");      pan4.add(b16,"North");    pan4.add(b17,"South");    pan4.add(b18,"East");    pan4.add(b19, "West");    pan4.add(b20,"Center");    pan5.add(b21,"North");    pan5.add(b22,"South");    pan5.add(b23,"East");    pan5.add(b24, "West");    pan5.add(b25,"Center");    jf.setVisible(true);    } }

将代码：pan1.setLayout(lay);　修改为：pan1.setLayout(new BorderLayout());　运行结果为：