我是一名初学程序员,试图制作一个简单的计算器。在我的代码结束时,我尝试让文本字段显示用户按下的任何按钮。由于某种原因,text.setText(“7”)不会显示在文本字段中。你能帮帮我吗?
import javax.swing.*; //imports all that is needed for the code
import java.awt.*;
import java.awt.event.*;
public class Calculator extends JFrame implements ActionListener {
public JButton button1, button2, button3, button4, button5, button6, button7, button8, button9, button10, button11, button12, button13, button14, button15, button16;
public JTextArea text;
public Calculator()
{
setSize(350,300); //sets size to 300 by 300 //LOOK UP HOW TO LOCK SIZE
setResizable(false); //does not let user change the size of the window
setDefaultCloseOperation(EXIT_ON_CLOSE);//makes app close when I press the x on the top left
Container contentPane = getContentPane();//gets the contentPane
contentPane.setBackground(Color.CYAN);//sets background color to white
contentPane.setLayout(new FlowLayout());//makes the contentPane read from left to right
JTextArea text = new JTextArea(1, 25);
contentPane.add(text);
text.setEditable(false);
button1 = new JButton ("7");
contentPane.add(button1);
button1.addActionListener(this);
button2 = new JButton ("8");
contentPane.add(button2);
button2.addActionListener(this);
button3 = new JButton ("9");
contentPane.add(button3);
button3.addActionListener(this);
button4 = new JButton ("÷");
contentPane.add(button4);
button4.addActionListener(this);
button5 = new JButton ("4");
contentPane.add(button5);
button5.addActionListener(this);
button6 = new JButton ("5");
contentPane.add(button6);
button6.addActionListener(this);
button7 = new JButton ("6");
contentPane.add(button7);
button7.addActionListener(this);
button8 = new JButton ("x");
contentPane.add(button8);
button8.addActionListener(this);
button9 = new JButton ("1");
contentPane.add(button9);
button9.addActionListener(this);
button10 = new JButton ("2");
contentPane.add(button10);
button10.addActionListener(this);
button11 = new JButton ("3");
contentPane.add(button11);
button11.addActionListener(this);
button12 = new JButton ("-");
contentPane.add(button12);
button12.addActionListener(this);
button13 = new JButton ("0");
contentPane.add(button13);
button13.addActionListener(this);
button14 = new JButton (".");
contentPane.add(button14);
button14.addActionListener(this);
button15 = new JButton ("=");
contentPane.add(button15);
button15.addActionListener(this);
button16 = new JButton ("+");
contentPane.add(button16);
button16.addActionListener(this);
}
public static void main(String[] args)
{
Calculator guiWindow = new Calculator(); //uses GUI
guiWindow.setVisible(true); //makes it visible
}
public void actionPerformed(ActionEvent e)
{
Container contentPane = getContentPane();
if (e.getActionCommand().equals("7"));
{
text.setText("7");
}
}
}
答案 0 :(得分:2)
看起来你在构造函数中隐藏了你的成员字段JTextArea text
。这意味着你没有将JTextArea的实例分配给成员字段,而是分配给构造函数中的局部变量。
使用而不是
JTextArea text = new JTextArea(1, 25);
此
text = new JTextArea(1, 25);