缺少 JTextField 并且布局错误地放置了 JButton

Posted 2023-03-17

【中文标题】缺少 JTextField 并且布局错误地放置了 JButton

【英文标题】：JTextField missing and Layout wrongly placing JButtons

【发布时间】：2014-02-17 15:58:54

【问题描述】：

我正在尝试使用 BorderLayout 将 afew 元素组合到 JPanel 中。 如果调用该构造函数，我在中心有一个 JSlider，在西边有一个 Name。然后在东边我有另一个面板来控制滑块，这个面板给出了所有的问题。

在东面板上，我想要一个 JTextField 和两个堆叠的按钮。我在中心有一个 JTextField，然后在东边有一个子面板，它在北/南保持按钮以使它们堆叠。

当我运行程序时，东面板缺少 JTextField 并且按钮的行为就像它们分别设置为西/东，而不是北/南。

以下是我编写并查看了好几个小时的代码：

import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.BorderLayout;
import java.awt.event.ActionListener;

/*
Made by vzybilly

Look of class:
____________________________________________________
|                    |          |            | [+] |
| <Name, if called>: | <Slider> | <Text box> |     |
|                    |          |            | [-] |
----------------------------------------------------
*/

public class AdjustableSlider extends JPanel implements javax.swing.event.ChangeListener, ActionListener

//slider for mouse input of values
   private JSlider me;
   //text box for manual input of values
   private JTextField val;


   //Make a slider with a textbox on the right and control buttons more right for 1 movement, buttons are stacked.
   public AdjustableSlider(int min, int max, int cur, int spacing)
      setLayout(new BorderLayout(0, 0));
      me = new JSlider();
      me.setName("");
      me.setMinimum(min);
      me.setPaintLabels(true);
      me.setPaintTicks(true);
      me.setMajorTickSpacing(spacing);
      me.setMaximum(max);
      me.setValue(cur);
      me.addChangeListener(this);
      add(me, BorderLayout.CENTER);
      JPanel adjusters = new JPanel();
      
         adjusters.setLayout(new BorderLayout(0, 0));
         val = new JTextField(""+cur, (""+max).length());
         val.addActionListener(this);
         adjusters.add(val, BorderLayout.CENTER);
         JPanel adjustersSub = new JPanel();
         
            adjusters.setLayout(new BorderLayout(0, 0));
            JButton up = new JButton("+");
            up.addActionListener(
                  new ActionListener()
                     public void actionPerformed(java.awt.event.ActionEvent evt) 
                        me.setValue(me.getValue()+1););
            JButton down = new JButton("-");
            down.addActionListener(
                  new ActionListener()
                     public void actionPerformed(java.awt.event.ActionEvent evt) 
                        me.setValue(me.getValue()-1););
            adjustersSub.add(up, BorderLayout.NORTH);
            adjustersSub.add(down, BorderLayout.SOUTH);
         
         adjusters.add(adjustersSub, BorderLayout.EAST);
      
      add(adjusters, BorderLayout.EAST);
   

   //add a name label to the Slider.
   public AdjustableSlider(int min, int max, int cur, int spacing, String name)
      this(min, max, cur, spacing);
      add(new JLabel(name+":"), BorderLayout.WEST);


      //slider updated, reflect.
   public void stateChanged(javax.swing.event.ChangeEvent e)
      System.out.println("Slid: " + me.getValue());
      val.setText(""+me.getValue());

      //textbox updated, reflect.
   public void actionPerformed(java.awt.event.ActionEvent evt) 
      System.out.println("Type: " + val.getText());
      tryint t = Integer.parseInt(val.getText());
         if(me.getValue()!=t) me.setValue(t);
      catch(Exception e)e.printStackTrace();


      //get the current value of this slider
   public int get()
      return me.getValue();

我刚刚开始这个程序，所以我的 JFrame 非常简单：

  JFrame frame = new JFrame();
  frame.setTitle("Frame");
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  //frame.setBounds(100, 100, 700, 500);
  frame.getContentPane().setLayout(new BorderLayout(0, 0));
  JPanel sliders = new JPanel();
  
     sliders.setLayout(new BorderLayout(0, 0));
  
  JPanel controls = new JPanel();
  
     controls.setLayout(new BorderLayout(0, 0));
     volume = new AdjustableSlider(0, 100, 90, 10, "Volume");
     controls.add(volume, BorderLayout.CENTER);
  
  frame.add(sliders, BorderLayout.CENTER);
  frame.add(controls, BorderLayout.SOUTH);
  frame.pack();
  frame.setVisible(true);

编辑：我已经更正并修复了一些涉及文本字段更新和正在更新的错误，新代码如下。

import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.BorderLayout;
import java.awt.event.ActionListener;

/*
Made by vzybilly

Look of class:
____________________________________________________
|                    |          |            | [+] |
| <Name, if called>: | <Slider> | <Text box> |     |
|                    |          |            | [-] |
----------------------------------------------------
*/

public class AdjustableSlider extends JPanel

//slider for mouse input of values
   private JSlider me;
   //text box for manual input of values
   private JTextField val;


   //Make a slider with a textbox on the right and control buttons more right for 1 movement, buttons are stacked.
   public AdjustableSlider(int min, int max, int cur, int spacing)
      setLayout(new BorderLayout(0, 0));
      me = new JSlider();
      me.setName("");
      me.setMinimum(min);
      me.setPaintLabels(true);
      me.setPaintTicks(true);
      me.setMajorTickSpacing(spacing);
      me.setMaximum(max);
      me.setValue(cur);
      me.addChangeListener(
            new javax.swing.event.ChangeListener()
               public void stateChanged(javax.swing.event.ChangeEvent e)
                  try
                     if(val.getText().length()<1||Integer.parseInt(val.getText())!=me.getValue())
                        val.setText(""+me.getValue());
                  catch(NumberFormatException nfe)val.setText(""+me.getValue()););
      add(me, BorderLayout.CENTER);
      JPanel adjusters = new JPanel();
      
         adjusters.setLayout(new BorderLayout(0, 0));
         val = new JTextField(""+cur, (""+max).length());
         val.addCaretListener(
               new javax.swing.event.CaretListener()
                  public void caretUpdate(javax.swing.event.CaretEvent ce)
                     tryint t = Integer.parseInt(val.getText());
                        if(me.getValue()!=t) me.setValue(t);
                     catch(NumberFormatException nfe)/*System.out.println("null input to box");*/
                     catch(Exception e)e.printStackTrace(););
         adjusters.add(val, BorderLayout.CENTER);
         JPanel adjustersSub = new JPanel();
         
            adjustersSub.setLayout(new BorderLayout(0, 0));
            JButton up = new JButton("+");
            up.addActionListener(
                  new ActionListener()
                     public void actionPerformed(java.awt.event.ActionEvent evt) 
                        me.setValue(me.getValue()+1););
            JButton down = new JButton("-");
            down.addActionListener(
                  new ActionListener()
                     public void actionPerformed(java.awt.event.ActionEvent evt) 
                        me.setValue(me.getValue()-1););
            adjustersSub.add(up, BorderLayout.NORTH);
            adjustersSub.add(down, BorderLayout.SOUTH);
         
         adjusters.add(adjustersSub, BorderLayout.EAST);
      
      add(adjusters, BorderLayout.EAST);
   

   //add a name label to the Slider.
   public AdjustableSlider(int min, int max, int cur, int spacing, String name)
      this(min, max, cur, spacing);
      add(new JLabel(name+":"), BorderLayout.WEST);


      //get the current value of this slider
   public int get()
      return me.getValue();

【参考方案1】：

这是一个错字问题，您的问题是在实例化 adjustersSub 之后，您重新定义了 adjusters 的布局

49c49
<             adjusters.setLayout(new BorderLayout(0, 0));
---
>             adjustersSub.setLayout(new BorderLayout(0, 0));

【讨论】：

谢谢，我现在觉得自己很傻...等我重新上网看看能不能上传修改...