带有按键响应的 Java 计算器

Question

所以我写了这个脚本；它有点像我找到并拼凑起来的计算器的大杂烩。

KeyListener 来自 Java - oracle - .com 网站。顺便说一句，我对此非常陌生，不知道我在做什么。

我正在尝试使用KeyListener来允许击键使计算器工作，这样就不必单击输入；目前脚本可以编译，但无法输入输入...我这样做对吗？

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;

public class Calculator extends JFrame implements KeyListener, ActionListener {

JPanel[] row = new JPanel[5];
JButton[] button = new JButton[19];
String[] buttonstring = {"7", "8", "9", "+",
                         "4", "5", "6", "-",
                         "1", "2", "3", "*",
                         ".", "/", "C", "SR",
                         "+/-", "=", "0"};
int[] dimW = {300,45,100,90};
int[] dimH = {35, 40};
Dimension displayDimension = new Dimension(dimW[0], dimH[0]);
Dimension regularDimension = new Dimension(dimW[1], dimH[1]);
Dimension rColumnDimension = new Dimension(dimW[2], dimH[1]);
Dimension zeroButDimension = new Dimension(dimW[3], dimH[1]);
boolean[] function = new boolean[4];
double[] temporary = {0, 0};
JTextArea display = new JTextArea(1,20);

Font font = new Font("Times new Roman", Font.BOLD, 14);
JTextArea displayArea;
JTextField typingArea;
static final String newline = System.getProperty("line.separator");

    //Uncomment this if you wish to turn off focus
    //traversal.  The focus subsystem consumes
    //focus traversal keys, such as Tab and Shift Tab.
    //If you uncomment the following line of code, this
    //disables focus traversal and the Tab events will
    //become available to the key event listener.
    //typingArea.setFocusTraversalKeysEnabled(false);


Calculator() {
    super("Calculator");
    setDesign();
    setSize(380, 250);
    setResizable(false);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    GridLayout grid = new GridLayout(5,5);
    setLayout(grid);

    for(int i = 0; i < 4; i++)
        function[i] = false;

    FlowLayout f1 = new FlowLayout(FlowLayout.CENTER);
    FlowLayout f2 = new FlowLayout(FlowLayout.CENTER,1,1);
    for(int i = 0; i < 5; i++)
        row[i] = new JPanel();
    row[0].setLayout(f1);
    for(int i = 1; i < 5; i++)
        row[i].setLayout(f2);

    for(int i = 0; i < 19; i++) {
        button[i] = new JButton();
        button[i].setText(buttonstring[i]);
        button[i].setFont(font);
        button[i].addActionListener(this);
    }

    display.setFont(font);
    display.setEditable(false);
    display.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
    display.setPreferredSize(displayDimension);
    for(int i = 0; i < 14; i++)
        button[i].setPreferredSize(regularDimension);
    for(int i = 14; i < 18; i++)
        button[i].setPreferredSize(rColumnDimension);
    button[18].setPreferredSize(zeroButDimension);

    row[0].add(display);
    add(row[0]);

    for(int i = 0; i < 4; i++)
        row[1].add(button[i]);
    row[1].add(button[14]);
    add(row[1]);

    for(int i = 4; i < 8; i++)
        row[2].add(button[i]);
    row[2].add(button[15]);
    add(row[2]);

    for(int i = 8; i < 12; i++)
        row[3].add(button[i]);
    row[3].add(button[16]);
    add(row[3]);

    row[4].add(button[18]);
    for(int i = 12; i < 14; i++)
        row[4].add(button[i]);
    row[4].add(button[17]);
    add(row[4]);

    setVisible(true);
}



public void clear() {
    try {
        display.setText("");
        for(int i = 0; i < 4; i++)
            function[i] = false;
        for(int i = 0; i < 2; i++)
            temporary[i] = 0;
    } catch(NullPointerException e) {  
    }
}

public void getSqrt() {
    try {
        double value = Math.sqrt(Double.parseDouble(display.getText()));
        display.setText(Double.toString(value));
    } catch(NumberFormatException e) {
    }
}

public void getPosNeg() {
    try {
        double value = Double.parseDouble(display.getText());
        if(value != 0) {
            value = value * (-1);
            display.setText(Double.toString(value));
        }
        else {
        }
    } catch(NumberFormatException e) {
    }
}

public void getResult() {
    double result = 0;
    temporary[1] = Double.parseDouble(display.getText());
    String temp0 = Double.toString(temporary[0]);
    String temp1 = Double.toString(temporary[1]);
    try {
        if(temp0.contains("-")) {
            String[] temp00 = temp0.split("-", 2);
            temporary[0] = (Double.parseDouble(temp00[1]) * -1);
        }
        if(temp1.contains("-")) {
            String[] temp11 = temp1.split("-", 2);
            temporary[1] = (Double.parseDouble(temp11[1]) * -1);
        }
    } catch(ArrayIndexOutOfBoundsException e) {
    }
    try {
        if(function[2] == true)
            result = temporary[0] * temporary[1];
        else if(function[3] == true)
            result = temporary[0] / temporary[1];
        else if(function[0] == true)
            result = temporary[0] + temporary[1];
        else if(function[1] == true)
            result = temporary[0] - temporary[1];
        display.setText(Double.toString(result));
        for(int i = 0; i < 4; i++)
            function[i] = false;
    } catch(NumberFormatException e) {
    }
}

public final void setDesign() {
    try {
        UIManager.setLookAndFeel(
                "com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
    } catch(Exception e) {   
    }
}

@Override
public void actionPerformed(ActionEvent ae) {
    if(ae.getSource() == button[0])
        display.append("7");
    if(ae.getSource() == button[1])
        display.append("8");
    if(ae.getSource() == button[2])
        display.append("9");
    if(ae.getSource() == button[3]) {
        //add function[0]
        temporary[0] = Double.parseDouble(display.getText());
        function[0] = true;
        display.setText("");
    }
    if(ae.getSource() == button[4])
        display.append("4");
    if(ae.getSource() == button[5])
        display.append("5");
    if(ae.getSource() == button[6])
        display.append("6");
    if(ae.getSource() == button[7]) {
        //subtract function[1]
        temporary[0] = Double.parseDouble(display.getText());
        function[1] = true;
        display.setText("");
    }
    if(ae.getSource() == button[8])
        display.append("1");
    if(ae.getSource() == button[9])
        display.append("2");
    if(ae.getSource() == button[10])
        display.append("3");
    if(ae.getSource() == button[11]) {
        //multiply function[2]
        temporary[0] = Double.parseDouble(display.getText());
        function[2] = true;
        display.setText("");
    }
    if(ae.getSource() == button[12])
        display.append(".");
    if(ae.getSource() == button[13]) {
        //divide function[3]
        temporary[0] = Double.parseDouble(display.getText());
        function[3] = true;
        display.setText("");
    }
    if(ae.getSource() == button[14])
        clear();
    if(ae.getSource() == button[15])
        getSqrt();
    if(ae.getSource() == button[16])
        getPosNeg();
    if(ae.getSource() == button[17])
        getResult();
    if(ae.getSource() == button[18])
        display.append("0");
}

public void contentPane() {
 typingArea = new JTextField(20);
    typingArea.addKeyListener(this);
   displayArea = new JTextArea();
       displayArea.setEditable(false);
       JScrollPane scrollPane = new JScrollPane(displayArea);
       scrollPane.setPreferredSize(new Dimension(375, 125));

       getContentPane().add(typingArea, BorderLayout.PAGE_START);  
       getContentPane().add(scrollPane, BorderLayout.CENTER); 


}

public void keyTyped(KeyEvent e) {
    displayInfo(e, "KEY TYPED: ");
}

/** Handle the key pressed event from the text field. */
public void keyPressed(KeyEvent e) {
    displayInfo(e, "KEY PRESSED: ");
}

/** Handle the key released event from the text field. */
public void keyReleased(KeyEvent e) {
    displayInfo(e, "KEY RELEASED: ");
}

/** Handle the button click. */
public void ActionPerformed(ActionEvent e) {
    //Clear the text components.
    displayArea.setText("");
    typingArea.setText("");

    //Return the focus to the typing area.
    typingArea.requestFocusInWindow();
}

private void displayInfo(KeyEvent e, String keyStatus){

    //You should only rely on the key char if the event
    //is a key typed event.
    int id = e.getID();
    String keyString;
    if (id == KeyEvent.KEY_TYPED) {
        char c = e.getKeyChar();
        keyString = "key character = '" + c + "'";
    }  else {
        int keyCode = e.getKeyCode();
        keyString = "key code = " + keyCode
                + " ("
                + KeyEvent.getKeyText(keyCode)
                + ")";
    }

    int modifiersEx = e.getModifiersEx();
    String modString = "extended modifiers = " + modifiersEx;
    String tmpString = KeyEvent.getModifiersExText(modifiersEx);
    if (tmpString.length() > 0) {
        modString += " (" + tmpString + ")";
    } else {
        modString += " (no extended modifiers)";
    }

    String actionString = "action key? ";
    if (e.isActionKey()) {
        actionString += "YES";
    } else {
        actionString += "NO";
    }

    String locationString = "key location: ";
    int location = e.getKeyLocation();
    if (location == KeyEvent.KEY_LOCATION_STANDARD) {
        locationString += "standard";
    } else if (location == KeyEvent.KEY_LOCATION_LEFT) {
        locationString += "left";
    } else if (location == KeyEvent.KEY_LOCATION_RIGHT) {
        locationString += "right";
    } else if (location == KeyEvent.KEY_LOCATION_NUMPAD) {
        locationString += "numpad";
    } else { // (location == KeyEvent.KEY_LOCATION_UNKNOWN)
        locationString += "unknown";
    }

    displayArea.append(keyStatus + newline
            + "    " + keyString + newline
            + "    " + modString + newline
            + "    " + actionString + newline
            + "    " + locationString + newline);
    displayArea.setCaretPosition(displayArea.getDocument().getLength()); 

}
public static void main(String[] arguments) {
Calculator c = new Calculator();
}
}

Answer 1

屏幕上的主要可见组件是display JTextArea。您将此字段设置为不可编辑，display.setEditable(false);，因此用户将无法在其中输入文本...

此外，永远不会调用 contentPane 方法，因此永远不会显示 typingArea 和 displayArea ，但我不确定您想要无论如何，请执行此操作，因为您已将布局管理器从 BorderLayout 更改为 GridLayout，这只会把事情搞砸......

此外，附加了 KeyListener 的 typingArea 永远不会添加到任何可显示组件中，因此它永远不会触发任何按键事件，因为没有人在其中键入内容。 ..

很难知道该建议什么，但我可能建议摆脱 display 和 displayArea 并使用 typingArea ，除非你确实需要多行数字...

无论如何，您应该避免在文本组件上使用 KeyListener，监听文本组件状态更改的更好解决方案是 DocumentListener，请参阅 Listening for Changes on a Document了解更多详情...