Question

JAVA 我用其他的布局方式都会有显示，但用BorderLayout就只出来一块白板是怎么回事啊，代码如下

import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import java.awt.BorderLayout;
class Calculator extends JFrame{
private JPanel pan= new JPanel();
private JButton button;
private JTextField text;
String number[]={"7","8","9","/","4","5","6","*","1","2","3","-","0",".","=","+"};
public Calculator() {
super("小神童计算器");
setSize(600,600);
setLayout(new BorderLayout(5,5));
setVisible(true);
text=new JTextField("请输入数字",20);
pan.setLayout(new GridLayout(4,4));
for(int i=0;i<12;i++){
button=new JButton(number[i]);
pan.add(button);
}
pan.setVisible(true);
//add(text,BorderLayout.NORTH);
add(pan,BorderLayout.CENTER);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
}
public class test {
public static void main(String [] args){
Calculator cal=new Calculator();
}
}
我是想写一个计算器的面板

Answer 1

把setVisible(true);这句移到public Calculator()构造函数的末尾,按钮就显示出来了,

另外for(int i=0;i<12;i++)应该改成for(int i=0;i<16;i++)因为你有16个按钮

完整的Java程序如下(改动的地方见注释)

import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import java.awt.BorderLayout;
class Calculator extends JFrame{
 private JPanel pan= new JPanel();
 private JButton button;
 private JTextField text;
 String number[]={"7","8","9","/","4","5","6","*","1","2","3","-","0",".","=","+"};
 public Calculator() {
  super("小神童计算器");
  setSize(600,600);
  setLayout(new BorderLayout(5,5));
  text=new JTextField("请输入数字",20);
  pan.setLayout(new GridLayout(4,4));
  for(int i=0;i<16;i++){ //这里i<12;改成i<16;
   button=new JButton(number[i]);
   pan.add(button);
  }
  pan.setVisible(true);
  //add(text,BorderLayout.NORTH);
  add(pan,BorderLayout.CENTER);
  setDefaultCloseOperation(EXIT_ON_CLOSE);
  setVisible(true);//这里把setVisible(true);移到这里
 }
}
public class test {
 public static void main(String [] args){
  Calculator cal=new Calculator();
 }
}

运行结果

Answer 2