我正在嘗試為課堂創建一個科學計算器。我不確定我哪里出錯了，但它不會將任何按鈕輸入列印到文本欄位中。有人知道我哪里出錯了嗎？問題來自代碼底部的“calc”類。我只對計算器進行了編碼以回應數字輸入，所以沒有其他按鈕可以作業，但是數字按鈕應該可以作業，我不知道如何修復它。我對編程還是很陌生
package scientificcalc;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class ScientificCalc extends JFrame {
JFrame Frame;
JPanel Panel;
JTextField Text;
JButton Button[]= new JButton[25]; // Array holds all calculator buttons
String val0, val1, val2; // Each val records a button pressed
public ScientificCalc() {
val0 = val1 = val2 = "";
Frame = new JFrame("Scientific Calculator");
Panel = new JPanel();
Panel.setBackground(Color.RED);
Text = new JTextField(20);
Text.setEditable(false);
Frame.setVisible(true);
Frame.setSize(400,400);
Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
ActionListener a = null;
// Following Lines create each button
Button[0] = new JButton("0");
Button[0].addActionListener(a);
Button[1] = new JButton("1");
Button[1].addActionListener(a);
Button[2] = new JButton("2");
Button[2].addActionListener(a);
Button[3] = new JButton("3");
Button[3].addActionListener(a);
Button[4] = new JButton("4");
Button[4].addActionListener(a);
Button[5] = new JButton("5");
Button[5].addActionListener(a);
Button[6] = new JButton("6");
Button[6].addActionListener(a);
Button[7] = new JButton("7");
Button[7].addActionListener(a);
Button[8] = new JButton("8");
Button[8].addActionListener(a);
Button[9] = new JButton("9");
Button[9].addActionListener(a);
Button[10] = new JButton(" ");
Button[10].addActionListener(a);
Button[11] = new JButton("-");
Button[11].addActionListener(a);
Button[12] = new JButton("*");
Button[12].addActionListener(a);
Button[13] = new JButton("/");
Button[13].addActionListener(a);
Button[14] = new JButton("SQRT");
Button[14].addActionListener(a);
Button[15] = new JButton("Sin");
Button[15].addActionListener(a);
Button[16] = new JButton("Cos");
Button[16].addActionListener(a);
Button[17] = new JButton("Tan");
Button[17].addActionListener(a);
Button[18] = new JButton("1/x");
Button[18].addActionListener(a);
Button[19] = new JButton("x^2");
Button[19].addActionListener(a);
Button[20] = new JButton("log");
Button[20].addActionListener(a);
Button[21] = new JButton("!");
Button[21].addActionListener(a);
Button[22] = new JButton(".");
Button[22].addActionListener(a);
Button[23] = new JButton("=");
Button[23].addActionListener(a);
Button[24] = new JButton("Clear");
Button[24].addActionListener(a);
// Following Lines add everything to Panel and Frame
Panel.add(Text);
Panel.add(Button[0]);
Panel.add(Button[1]);
Panel.add(Button[2]);
Panel.add(Button[3]);
Panel.add(Button[4]);
Panel.add(Button[5]);
Panel.add(Button[6]);
Panel.add(Button[7]);
Panel.add(Button[8]);
Panel.add(Button[9]);
Panel.add(Button[10]);
Panel.add(Button[11]);
Panel.add(Button[12]);
Panel.add(Button[13]);
Panel.add(Button[14]);
Panel.add(Button[15]);
Panel.add(Button[16]);
Panel.add(Button[17]);
Panel.add(Button[18]);
Panel.add(Button[19]);
Panel.add(Button[20]);
Panel.add(Button[21]);
Panel.add(Button[22]);
Panel.add(Button[23]);
Panel.add(Button[24]);
Frame.add(Panel);
}
public class calc implements ActionListener {
public void actionPerformed(ActionEvent e) {
String i = e.getActionCommand();
if ((i.charAt(0) >= '0' && i.charAt(0) <= '9') || i.charAt(0) == '.') {
if (!val1.equals("")) {
val2 = val2 i;
} else {
val0 = val0 i; // Sets location of each digit when button is pressed
}
Text.setText(val0 val1 val2);
}
}
}
public static void main(String[] args) {
new ScientificCalc();
}
}
uj5u.com熱心網友回復：
您當前正在將您a設定為的 ActionListener 添加null到所有按鈕。更改ActionListener a = null為ActionListener a = new calc();
uj5u.com熱心網友回復：
您忘記通過以下方式初始化 calc 物件ActionListener a = new calc();
- 使用以小寫字母開頭的欄位名稱！
- 使用回圈而不是重復的代碼！
- 以大寫字母開頭的類名！
- 通過 CustomActionListener 命名 calc 類 下面有漂亮的代碼！
問題：如果它總是錯誤的，為什么要檢查它？if (!val1.equals(""))
package scientificcalc;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class ScientificCalc extends JFrame {
JFrame frame;
JPanel panel;
JTextField textField;
JButton[] buttonArray = new JButton[25]; // Array holds all calculator buttons
String val0, val1, val2; // Each val records a button pressed
public ScientificCalc() {
val0 = val1 = val2 = "";
frame = new JFrame("Scientific Calculator");
panel = new JPanel();
panel.setBackground(Color.RED);
textField = new JTextField(20);
textField.setEditable(false);
frame.setVisible(true);
frame.setSize(400, 400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
CustomActionListener actionListener = new CustomActionListener();
// Following Lines create each button
buttonArray[0] = new JButton("0");
buttonArray[1] = new JButton("1");
buttonArray[2] = new JButton("2");
buttonArray[3] = new JButton("3");
buttonArray[4] = new JButton("4");
buttonArray[5] = new JButton("5");
buttonArray[6] = new JButton("6");
buttonArray[7] = new JButton("7");
buttonArray[8] = new JButton("8");
buttonArray[9] = new JButton("9");
buttonArray[10] = new JButton(" ");
buttonArray[11] = new JButton("-");
buttonArray[12] = new JButton("*");
buttonArray[13] = new JButton("/");
buttonArray[14] = new JButton("SQRT");
buttonArray[15] = new JButton("Sin");
buttonArray[16] = new JButton("Cos");
buttonArray[17] = new JButton("Tan");
buttonArray[18] = new JButton("1/x");
buttonArray[19] = new JButton("x^2");
buttonArray[20] = new JButton("log");
buttonArray[21] = new JButton("!");
buttonArray[22] = new JButton(".");
buttonArray[23] = new JButton("=");
buttonArray[24] = new JButton("Clear");
for (int i = 0; i < buttonArray.length; i ) {
buttonArray[i].addActionListener(actionListener);
}
// Following Lines add everything to Panel and Frame
panel.add(textField);
for (JButton jButton : buttonArray) {
panel.add(jButton);
}
frame.add(panel);
}
class CustomActionListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
String i = e.getActionCommand();
if ((i.charAt(0) >= '0' && i.charAt(0) <= '9') || i.charAt(0) == '.') {
if (!val1.equals("")) {
val2 = val2 i;
} else {
val0 = val0 i; // Sets location of each digit when button is pressed
}
textField.setText(val0 val1 val2);
}
}
}
public static void main(String[] args) {
new ScientificCalc();
}
}
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