从按钮中获取文本到选定的文本域

Question

我是java programming的新手。我想执行一个任务，当按下按钮时，即从附加代码的JFrame中显示0-9时，该按钮的值必须被分配给在按下按钮之前选择的JField。如何操作？

import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

import javax.swing.*; 

class calci2 extends JFrame implements ActionListener { 
    JFrame f1; 
    JPanel p; 
    JButton b[] = new JButton[10]; 
    JButton btnadd; 
    JButton btnmul; 
    JButton btndiv; 
    JButton btnsub; 
    public static JTextField t1; 
    JTextField t2; 
    JTextField t3; 
    JLabel no1; 
    JLabel no2; 
    JLabel res; 

    calci2() { 
     f1 = new JFrame(); 
     p = new JPanel(); 
     t1 = new JTextField(15); 
     t2 = new JTextField(15); 
     t3 = new JTextField(15); 
     no1 = new JLabel("Enter 1st number"); 
     no2 = new JLabel("Enter 2nd number"); 
     res = new JLabel(" Result is  "); 
     btnadd = new JButton("ADD"); 
     btnmul = new JButton("MUL"); 
     btndiv = new JButton("DIV"); 
     btnsub = new JButton("SUB"); 
     for (int i = 0; i < 10; i++) { 
      b[i] = new JButton("" + i); 
     } 
     btnadd.addActionListener(this); 
     btnmul.addActionListener(this); 
     btndiv.addActionListener(this); 
     btnsub.addActionListener(this); 

     for (int i = 0; i < 10; i++) { 
      b[i].addActionListener(this); 
     } 
     p.add(no1); 
     p.add(t1); 
     p.add(no2); 
     p.add(t2); 
     p.add(res); 
     p.add(t3); 
     p.add(btnadd); 
     p.add(btnmul); 
     p.add(btndiv); 
     p.add(btnsub); 

     for (int i = 0; i < 10; i++) { 
      p.add(b[i]); 
     } 
     this.add(p); 
    } 

    public static void main(String args[]) { 
     calci2 c = new calci2(); 
     c.setDefaultCloseOperation(EXIT_ON_CLOSE); 
     c.setSize(300, 300); 
     c.setVisible(true); 
     c.setResizable(false); 
     c.setLocationRelativeTo(null); 
    } 

    public void actionPerformed(ActionEvent e) { 
     String str = e.getActionCommand(); 
     String s1 = new String(t1.getText()); 
     String s2 = new String(t2.getText()); 
     String s3 = new String(); 
     int a = Integer.parseInt(s1); 
     int b = Integer.parseInt(s2); 
     if (str.equals("ADD")) { 
      int c = a + b; 
      s3 = String.valueOf(c); 
      t3.setText(s3); 
     } 

     else if (str.equals("SUB")) { 
      int c = a - b; 
      s3 = String.valueOf(c); 
      t3.setText(s3); 
     } 

     else if (str.equals("MUL")) { 
      int c = a * b; 
      s3 = String.valueOf(c); 
      t3.setText(s3); 
     } 

     else if (str.equals("DIV")) { 
      int c = a/b; 
      s3 = String.valueOf(c); 
      t3.setText(s3); 
     } 
    } 
}; 

Answer 1

要检查哪些文本字段现在被选中，你可以在类T1和T2创建两个布尔值，我不认为你需要第三个用于T3

让我们说：

boolean t1_selected = false; 
boolean t2_selected = false; 

然后在Const中添加另一个侦听器。该文本字段是焦点监听者，注重听众将火当文本字段获得关注，那么你就可以在这个文本的布尔值更改为true有

 t1.addFocusListener(new FocusListener() { 

     @Override 
     public void focusLost(FocusEvent arg0) { 
      // TODO Auto-generated method stub 

     } 

     @Override 
     public void focusGained(FocusEvent arg0) { 
      // TODO Auto-generated method stub 
      t1_selected = true; 
      t2_selected = false; 
     } 
    }); 
    t2.addFocusListener(new FocusListener() { 

     @Override 
     public void focusLost(FocusEvent e) { 
      // TODO Auto-generated method stub 

     } 

     @Override 
     public void focusGained(FocusEvent e) { 
      // TODO Auto-generated method stub 
      t1_selected = false; 
      t2_selected = true; 
     } 
    }); 

现在的按钮，你需要检查对于函数actionPerformed中事件的来源，对所有按钮使用e.getSource（）而不是e.getActionCommand（）。

例如：

if(e.getSource() == this.b[0]){ 
     if(t1_selected) 
     { 
      t1.setText("0"); 
     } 
     if(t2_selected) 
     { 
      t2.setText("0"); 
     } 
    } 
    else if(e.getSource() == this.b[1]){ 
     if(t1_selected) 
     { 
      t1.setText("1"); 
     } 
     if(t2_selected) 
     { 
      t2.setText("1"); 
     } 
    } 
      //rest of cases 

还没有把这些线在开始的功能

 String s1 = new String(t1.getText()); 
     String s2 = new String(t2.getText()); 
     String s3 = new String(); 
     int a = Integer.parseInt(s1); 
     int b = Integer.parseInt(s2); 

，他们将通过异常，如果文本字段为空，把它们只在里面ADD，SUB，DIV的情况下和MUL

例如：

else if (e.getSource() == btnadd) { 
     String s1 = new String(t1.getText()); 
     String s2 = new String(t2.getText()); 
     String s3 = new String(); 
     int a = Integer.parseInt(s1); 
     int b = Integer.parseInt(s2); 

     int c = a + b; 
     s3 = String.valueOf(c); 
     t3.setText(s3); 
    } 

顺便说一句，你必须在发布前缩进代码，这是你的工作，使你的问题一个干净的