Question

我帮助创建了一个计算器。例如5 + 3 = 8.0，当我在示例3中显示结果之后按下新数字时，它将仅添加到旧结果，8.3，而不是清除，只是自己键入3。如果我能得到一些帮助，我将非常感激我一直在努力解决它，但我无法让它发挥作用。

/ noob程序员

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

public class Calculator extends JFrame implements ActionListener {

    JPanel[] row = new JPanel[5];
    JButton[] button = new JButton[19];
    String[] buttonString = {"7", "8", "9", "+",
                             "4", "5", "6", "-",
                             "1", "2", "3", "*",
                             ".", "/", "C", "√",
                             "+/-", "=", "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);

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

Answer 1

这是预期的行为，因为您无法在任何情况下清除文本。您需要维护应用程序的状态（可能使用标记），然后根据应用程序的状态，clear或append文本

Answer 2

所以这是一个有效的解决方案。

首先，您的类现在实现了MouseListener。在第7行中，我添加了布尔值来决定是否提示结果。

private boolean resultPrompted = false;

在第52行中，每个按钮都有自己的MouseListener。

button[i].addMouseListener(this);

在第151行中，已提示结果，因此我们将布尔值设置为true

resultPrompted = true;

在第234至240行中，＆＃34;魔法＆＃34;发生。在这里，您可以确定最近是否提示结果。如果是这样，我们删除当前的显示内容。当前键入的字符单独显示。

完成。

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

public class Calculator extends JFrame implements ActionListener, MouseListener {

private boolean resultPrompted = false;

JPanel[] row = new JPanel[5];
JButton[] button = new JButton[19];
String[] buttonString = {"7", "8", "9", "+",
    "4", "5", "6", "-",
    "1", "2", "3", "*",
    ".", "/", "C", "√",
    "+/-", "=", "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);

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);
        button[i].addMouseListener(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));

        resultPrompted = true;

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

@Override
public void mouseClicked(MouseEvent e) {

}

public void mousePressed (MouseEvent event){

    if(resultPrompted == true){
        clear();
        resultPrompted = false;
    }
}

@Override
public void mouseReleased(MouseEvent e) {

}

@Override
public void mouseEntered(MouseEvent e) {

}

@Override
public void mouseExited(MouseEvent e) {

}
}

按下新号码时计算器清除结果

2 个答案: