Question

java 在JTextArea中显示 滚动条

我的代码为什么不显示垂直滚动条 是那里错了么 如果有错 求高手修改

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class Cai {

private JFrame _frame;
private JPanel _panelMain;
private JPanel _panelCai;
private JPanel _panelArea;
private JButton _bntCai;
private JTextArea _txtArea;
private JLabel _lbl;
private JTextField _txt;
private JScrollPane _jsp;

public Cai(){
_frame=new JFrame();
_panelMain=new JPanel(new BorderLayout());
_panelCai=new JPanel();
_lbl=new JLabel("请猜1-10之间的数字：");
_panelArea=new JPanel();
_txt=new JTextField(3);
_txtArea=new JTextArea();
_bntCai=new JButton("猜");
_jsp=new JScrollPane(_txtArea);

_panelArea.add(_txtArea);
_panelCai.add(_lbl);
_panelCai.add(_txt);
_panelCai.add(_bntCai);
_panelMain.add(_panelCai,BorderLayout.NORTH);
_panelMain.add(_txtArea,BorderLayout.CENTER);

//_panelMain.add(_jsp,BorderLayout.EAST);
_jsp.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
_frame.setContentPane(_panelMain);

_frame.setBounds(300,300,300,300);
_frame.setVisible(true);

}
}

public static void main(String[] args) {

Cai a =new Cai();
}

Answer 1

你的代码里面并没有把_jsp添加到_panelMain里面，所以没有显示。而且还有些其他的问题，看下面的代码：

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

public class Cai {

private JFrame _frame;
private JPanel _panelMain;
private JPanel _panelCai;
private JPanel _panelArea;
private JButton _bntCai;
private JTextArea _txtArea;
private JLabel _lbl;
private JTextField _txt;
private JScrollPane _jsp;

public Cai() {
_frame = new JFrame();

_frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//点击右上角的关闭按钮时退出程序运行

_panelMain = new JPanel(new BorderLayout());
_panelCai = new JPanel();

_lbl = new JLabel("请猜1-10之间的数字：");
_txt = new JTextField(3);
_bntCai = new JButton("猜");

_panelArea = new JPanel(new BorderLayout());
//设置BorderLayout，让_txtArea自动充满

_txtArea = new JTextArea();

_txtArea.setLineWrap(true);
//_txtArea自动换行

_jsp = new JScrollPane(_panelArea);
//_jsp 以_panelArea为Viewport

_jsp.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

_panelArea.add(_txtArea);
_panelCai.add(_lbl);
_panelCai.add(_txt);
_panelCai.add(_bntCai);
_panelMain.add(_panelCai, BorderLayout.NORTH);
_panelMain.add(_jsp, BorderLayout.CENTER);
//添加_jsp在 BorderLayout.CENTER

_frame.setContentPane(_panelMain);

_frame.setBounds(300, 300, 300, 300);
_frame.setVisible(true);

}

public static void main(String[] args) {

Cai a = new Cai();
}
}