我不能让我的 -/+按钮工作（计算器）

-1

我正在学习Java。我正在为练习编程一个计算器，但是我不能得到+/-按钮的工作。该按钮应该使数字为负数/正数。例如，如果您输入5 + 3并且想要3为-3，那么它只会删除5+，并且只显示-3。我不能让我的 -/+按钮工作（计算器）

下面是代码：

计算器类：

package me.lommeregner.main; 

public class Main { 

    public static String tal = ""; //tal means number 
    public static float first = 0; 
    public static float second = 0; 
    public static int operator; 
    static float oper = 0; 
    static JTextField jtf = new JTextField(); 
    public static boolean minplu = false; 

    public static void main(String[] args) { 

    jtf.setPreferredSize(new Dimension(250,40)); 
    Scanner test = new Scanner(System.in); 

    final Button jbn0 = new Button("0", 0); 
    final Button jbn1 = new Button("1", 1); 
    final Button jbn2 = new Button("2", 2); 
    final Button jbn3 = new Button("3", 3); 
    final Button jbn4 = new Button("4", 4); 
    final Button jbn5 = new Button("5", 5); 
    final Button jbn6 = new Button("6", 6); 
    final Button jbn7 = new Button("7", 7); 
    final Button jbn8 = new Button("8", 8); 
    final Button jbn9 = new Button("9", 9); 


    final Button jbKomma = new Button("."); 
    final Button jbnepo = new Button("+/-"); //the button i need help with 



    final Button jbPlus = new Button(" + "); 
    final Button jbMinus = new Button(" - "); 
    final Button jbGange = new Button(" * "); 
    final Button jbDivition = new Button("/"); 
    final Button jbClear = new Button("C"); 
    final Button jbClearEntity = new Button("CE"); 
    final Button jbErLigMed = new Button(" = "); 



    //North 
    JPanel panelNorth = new JPanel(); 
    panelNorth.add(jtf); 

    //East 
    JPanel panelEast = new JPanel(); 
    panelEast.setLayout(new GridLayout(4, 1)); 
    panelEast.add(jbPlus); 
    panelEast.add(jbMinus); 
    panelEast.add(jbGange); 
    panelEast.add(jbDivition); 
    panelEast.add(jbErLigMed); 
    panelEast.add(jbClear); 
    panelEast.add(jbClearEntity); 


    //Center 
    JPanel panelCenter = new JPanel(); 
    panelCenter.setLayout(new GridLayout(3,3)); 
    panelCenter.add(jbn0); 
    panelCenter.add(jbn1); 
    panelCenter.add(jbn2); 
    panelCenter.add(jbn3); 
    panelCenter.add(jbn4); 
    panelCenter.add(jbn5); 
    panelCenter.add(jbn6); 
    panelCenter.add(jbn7); 
    panelCenter.add(jbn8); 
    panelCenter.add(jbn9); 
    panelCenter.add(jbKomma); 
    panelCenter.add(jbnepo); 


    //Main Panel 
    JPanel panel = new JPanel(); 
    panel.setLayout(new BorderLayout()); 
    panel.add(panelNorth, BorderLayout.NORTH); 
    panel.add(panelEast, BorderLayout.EAST); 
    panel.add(panelCenter, BorderLayout.CENTER); 


    //Frame 
    GameWindow frame = new GameWindow("Lommeregner - "+randomMessage(), 315, 350); 



    frame.setVisible(true); 
    frame.add(panel); 
    /*test.next(); 
    System.out.println(frame.size());*/ 




    //actionListeners 

    //Numbers 

    jbn0.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbn0.value); 
      tal = tal+jbn0.value;  //tal means number 
     }}); 
    jbn1.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbn1.value); 
      tal = tal+jbn1.value;  //tal means number 
     }}); 
    jbn2.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbn2.value); 
      tal = tal+jbn2.value; 
     }}); 
    jbn3.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbn3.value); 
      tal = tal+jbn3.value; 
     }}); 
    jbn4.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbn4.value); 
      tal = tal+jbn4.value; 
     }}); 
    jbn5.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbn5.value); 
      tal = tal+jbn5.value; 
     }}); 
    jbn6.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbn6.value); 
      tal = tal+jbn6.value; 
     }}); 
    jbn7.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbn7.value); 
      tal = tal+jbn7.value; 
     }}); 
    jbn8.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbn8.value); 
      tal = tal+jbn8.value; 
     }}); 
    jbn9.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbn9.value); 
      tal = tal+jbn9.value; 
     }}); 

    //operators 

    jbKomma.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(jtf.getText()+jbKomma.name); 
      tal = tal+jbKomma.name; 
     }}); 

    jbnepo.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      String text = jtf.getText(); 
      if(tal.length() !=0 && minplu !=true && second == 0){ 
       System.out.println(first); 
      minplu = true; 
      jtf.setText("-"+tal); 
      tal = "-"+tal; 
      text = ""; 
      }else if(tal.length() != 0 && minplu == true && second == 0){ 
       minplu = false; 
       tal = tal.substring(1, tal.length()); 
       System.out.println(tal); 
       jtf.setText(text.substring(1, text.length())); 
       text = ""; 
      }else if(tal.length() != 0 && minplu == true && second != 0){ 
       minplu = false; 
       tal = tal.substring(1, tal.length()); 
       System.out.println(tal); 
       jtf.setText(tal+text.substring(tal.length() - text.length(), text.length())); 
       text = ""; 
      } 

     }}); 

    jbPlus.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      if(jtf.getText().length() !=0){ 
      jtf.setText(jtf.getText()+jbPlus.getText()); 
      first = Float.parseFloat(tal); 
      tal = ""; 
      operator = 1; 
     }}}); 
    jbMinus.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      if(jtf.getText().length() !=0){ 
      jtf.setText(jtf.getText()+jbMinus.getText()); 
      first = Float.parseFloat(tal); 
      tal = ""; 
      operator = 2; 
      }}}); 
    jbGange.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      if(jtf.getText().length() !=0){ 
      jtf.setText(jtf.getText()+jbGange.getText()); 
      first = Float.parseFloat(tal); 
      tal = ""; 
      operator = 3; 
     }}}); 
    jbDivition.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      if(jtf.getText().length() !=0){ 
      jtf.setText(jtf.getText()+jbDivition.getText()); 
      first = Float.parseFloat(tal); 
      tal = ""; 
      operator = 4; 
      }}}); 
    jbErLigMed.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      if(jtf.getText().length() !=0){ 
      second = Float.parseFloat(tal); 
      if(operator == 1)oper = first + second; 
      if(operator == 2)oper = first - second; 
      if(operator == 3)oper = first * second; 
      if(operator == 4)oper = first/second; 
      jtf.setText(jtf.getText()+jbErLigMed.getText()+oper); 
      tal =""; 
     }}}); 
    jbClear.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      jtf.setText(""); 
      oper = 0; 
      second = 0; 
      first = 0; 
      tal=""; 

     }}); 
    jbClearEntity.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) { 
      String text = jtf.getText(); 
      if(tal.length() !=0) 
      tal = tal.substring(0, tal.length() - 1); 
      if(text.length() !=0) 
      jtf.setText(text.substring(0, text.length() - 1)); 
      System.out.println(tal); 
     }});   
    } 


    // random message i made for fun 
    public static String randomMessage(){ 

    Random r = new Random(); 

    String[] message = {"17 * 17 = "+17*17, "What is 10 * 10??", "This is a calculator", "Have u found the secret spot yet??", "QUICK PRESS alt-F4!!!!", "Welcome", ""}; 

    int ri =r.nextInt(message.length - 1); 

    return message[ri]; 
    } 
}

Button类：

package me.lommeregner.main; 

import javax.swing.JButton; 

public class Button extends JButton{ 

    boolean operator; 
    int value; 
    String name; 

    public Button(String name) { 
    this.setText(name); 
    this.name = name; 
    operator = true; 
    } 

    public Button(String name, int value) { 
    this.setText(name); 
    this.value = value; 
    operator = false; 
    } 

    public void setValue(int value) { 
    this.value = value; 
    } 

    public void setOperator(boolean operator) { 
    this.operator = operator; 
    } 

    public int getValue() { 
    return value; 
    } 

    private boolean getOperator() { 
    return operator; 
    } 
}

GameWindow类：

package me.lommeregner.main; 

import javax.swing.JFrame; 

public class GameWindow extends JFrame { 

    public GameWindow(String title, int width, int height) { 
     setTitle(title); 
     setSize(width, height); 
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     setLocationRelativeTo(null); 
     setResizable(true); 

    } 
}

来源

2015-09-11 Jonas m.

您的文章甚至没有包含所有的代码。 GameWindow类定义在哪里？ –

“+/-”是否将最后输入的数字乘以“-1”？ – Ian2thedv

@DušanRychnovský我已经添加了gamewindow类。我之前没加过它，因为我没想到你需要它。 –

不会解决你的实际问题，但这里有更好地构建一些建议代码：

不要叫你的类“按钮”。这个名称有一个AWT类。让你的课更具描述性。
不要使用最终变量。
不要在main（）方法中创建计算器。 main（）方法应该用来创建你的计算器应用程序。例如，你可能有一个JPanel代表计算器。然后，所有需要的变量/方法将在该类中定义。
某些按钮（如1,2,3,4 ...）提供了常用的功能，因此提供了一个通用的ActionListener，因此您不需要重复该代码10次。

例如：

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

public class CalculatorPanel extends JPanel 
{ 
    private JTextField display; 

    public CalculatorPanel() 
    { 
     Action numberAction = new AbstractAction() 
     { 
      @Override 
      public void actionPerformed(ActionEvent e) 
      { 
//    display.setCaretPosition(display.getDocument().getLength()); 
       display.replaceSelection(e.getActionCommand()); 
      } 
     }; 

     setLayout(new BorderLayout()); 

     display = new JTextField(); 
     display.setEditable(false); 
     display.setHorizontalAlignment(JTextField.RIGHT); 
     add(display, BorderLayout.NORTH); 

     JPanel buttonPanel = new JPanel(); 
     buttonPanel.setLayout(new GridLayout(0, 5)); 
     add(buttonPanel, BorderLayout.CENTER); 

     for (int i = 0; i < 10; i++) 
     { 
      String text = String.valueOf(i); 
      JButton button = new JButton(text); 
      button.addActionListener(numberAction); 
      button.setBorder(new LineBorder(Color.BLACK)); 
      button.setPreferredSize(new Dimension(30, 30)); 
      buttonPanel.add(button); 

      InputMap inputMap = button.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW); 
      inputMap.put(KeyStroke.getKeyStroke(text), text); 
      inputMap.put(KeyStroke.getKeyStroke("NUMPAD" + text), text); 
      button.getActionMap().put(text, numberAction); 
     } 
    } 

    private static void createAndShowUI() 
    { 
     JFrame frame = new JFrame("Calculator Panel"); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.add(new CalculatorPanel()); 
     frame.pack(); 
     frame.setLocationRelativeTo(null); 
     frame.setVisible(true); 
    } 

    public static void main(String[] args) 
    { 
     EventQueue.invokeLater(new Runnable() 
     { 
      public void run() 
      { 
       createAndShowUI(); 
      } 
     }); 
    } 
}

来源

2015-09-11 15:17:08 camickr

好，谢谢，u能解释这是什么意思：EventQueue.invokeLater（新的Runnable（）{ 公共无效的run（）{ createAndShowUI（）;} }）; –

@Jonasm，所有的Swing组件都应该在'Event Dispatch Thread'上创建/更新。阅读[Concurrency]上的Swing教程部分（http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html）以获取更多信息。 – camickr

我不能让我的 -/+按钮工作（计算器）

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