我想创建一个计算器，我遇到了一些问题

Question

我遇到的麻烦是我无法弄清楚如何使+， - ，和*按钮来保存数字我之前输入过，然后在按=按钮后再使用该号码。我也遇到了使=按钮识别我按下的四个按钮中的哪些的问题，以便当按下 - 按钮时它被扣除，而不是相反。

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

public class Calculator extends JFrame implements ActionListener{ 

    JPanel row1 = new JPanel(); 
    JTextField display = new JTextField("0"); 
    Font font = new Font("Calibri", Font.PLAIN, 24); 

    JPanel row2 = new JPanel(); 
    JButton c = new JButton("C"); 

    JPanel row3 = new JPanel(); 
    JButton num7 = new JButton("7"); 
    JButton num8 = new JButton("8"); 
    JButton num9 = new JButton("9"); 
    JButton divide = new JButton("/"); 

    JPanel row4 = new JPanel(); 
    JButton num4 = new JButton("4"); 
    JButton num5 = new JButton("5"); 
    JButton num6 = new JButton("6"); 
    JButton multiply = new JButton("*"); 

    JPanel row5 = new JPanel(); 
    JButton num1 = new JButton("1"); 
    JButton num2 = new JButton("2"); 
    JButton num3 = new JButton("3"); 
    JButton minus = new JButton("-"); 

    JPanel row6 = new JPanel(); 
    JButton num0 = new JButton("0"); 
    JButton dot = new JButton("."); 
    JButton equals = new JButton("="); 
    JButton plus = new JButton("+"); 

    public Calculator(){ 
    super("Calculator"); 
    setSize(450,275); 
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    GridLayout layout = new GridLayout(6,1); 
    setLayout(layout); 

    display.setFont(font); 
    display.setEnabled(false); 
    GridLayout layout1 = new GridLayout(1,1); 
    row1.setLayout(layout1); 
    row1.add(display); 
    add(row1); 

    c.addActionListener(this); 
    c.setFont(font); 
    row2.setLayout(layout1); 
    row2.add(c); 
    add(row2); 

    num7.setFont(font); 
    num8.setFont(font); 
    num9.setFont(font); 
    divide.setFont(font); 
    num7.addActionListener(this); 
    num8.addActionListener(this); 
    num9.addActionListener(this); 
    divide.addActionListener(this); 
    GridLayout layout2 = new GridLayout(1,4); 
    row3.setLayout(layout2); 
    row3.add(num7); 
    row3.add(num8); 
    row3.add(num9); 
    row3.add(divide); 
    add(row3); 

    num4.setFont(font); 
    num5.setFont(font); 
    num6.setFont(font); 
    multiply.setFont(font); 
    num4.addActionListener(this); 
    num5.addActionListener(this); 
    num6.addActionListener(this); 
    multiply.addActionListener(this); 
    row4.setLayout(layout2); 
    row4.add(num4); 
    row4.add(num5); 
    row4.add(num6); 
    row4.add(multiply); 
    add(row4); 

    num1.setFont(font); 
    num2.setFont(font); 
    num3.setFont(font); 
    minus.setFont(font); 
    num1.addActionListener(this); 
    num2.addActionListener(this); 
    num3.addActionListener(this); 
    minus.addActionListener(this); 
    row5.setLayout(layout2); 
    row5.add(num1); 
    row5.add(num2); 
    row5.add(num3); 
    row5.add(minus); 
    add(row5); 

    num0.setFont(font); 
    dot.setFont(font); 
    equals.setFont(font); 
    plus.setFont(font); 
    num0.addActionListener(this); 
    dot.addActionListener(this); 
    equals.addActionListener(this); 
    plus.addActionListener(this); 
    row6.setLayout(layout2); 
    row6.add(num0); 
    row6.add(dot); 
    row6.add(equals); 
    row6.add(plus); 
    add(row6); 

    setVisible(true); 
    } 

    public void actionPerformed(ActionEvent e){ 
     String button = e.getActionCommand(); 
     if(button.equals("C")){ 
      display.setText("0"); 
     } 
     if(button.equals("7")){ 
      int num = 7; 
      int prevNum = Integer.parseInt(display.getText()); 
      display.setText("" + prevNum + num); 
     } 
     if(button.equals("8")){ 
      int num = 8; 
      int prevNum = Integer.parseInt(display.getText()); 
      display.setText("" + prevNum + num); 
     } 
     if(button.equals("9")){ 
      int num = 9; 
      int prevNum = Integer.parseInt(display.getText()); 
      display.setText("" + prevNum + num); 
     } 
     if(button.equals("4")){ 
      int num = 4; 
      int prevNum = Integer.parseInt(display.getText()); 
      display.setText("" + prevNum + num); 
     } 
     if(button.equals("5")){ 
      int num = 5; 
      int prevNum = Integer.parseInt(display.getText()); 
      display.setText("" + prevNum + num); 
     } 
     if(button.equals("6")){ 
      int num = 6; 
      int prevNum = Integer.parseInt(display.getText()); 
      display.setText("" + prevNum + num); 
     } 
     if(button.equals("1")){ 
      int num = 1; 
      int prevNum = Integer.parseInt(display.getText()); 
      display.setText("" + prevNum + num); 
     } 
     if(button.equals("2")){ 
      int num = 2; 
      int prevNum = Integer.parseInt(display.getText()); 
      display.setText("" + prevNum + num); 
     } 
     if(button.equals("3")){ 
      int num = 3; 
      int prevNum = Integer.parseInt(display.getText()); 
      display.setText("" + prevNum + num); 
     } 
     if(button.equals("0")){ 
      int num = 0; 
      int prevNum = Integer.parseInt(display.getText()); 
      display.setText("" + prevNum + num); 
     } 
    } 

    public static void main(String[] args){ 
     Calculator frame = new Calculator(); 
    } 
} 

Answer 1

您可以使用逻辑与此程序：

package com.nkb.calci; 

import android.app.Activity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.Button; 
import android.widget.EditText; 

public class SimpleCalculatorActivity extends Activity { 
    /** Called when the activity is first created. */ 
    EditText disp; 
    Button b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,bplus,bminus,binto,bby,bdot,bclear,bequals; 
    float op1,op2; 
    char op='\0'; 
    int state=1,decimalPoint=0; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 

    b0=(Button) findViewById(R.id.button0); 
    b1=(Button) findViewById(R.id.button1); 
    b2=(Button) findViewById(R.id.button2); 
    b3=(Button) findViewById(R.id.button3); 
    b4=(Button) findViewById(R.id.button4); 
    b5=(Button) findViewById(R.id.button5); 
    b6=(Button) findViewById(R.id.button6); 
    b7=(Button) findViewById(R.id.button7); 
    b8=(Button) findViewById(R.id.button8); 
    b9=(Button) findViewById(R.id.button9); 
    bplus=(Button) findViewById(R.id.buttonplus); 
    bminus=(Button) findViewById(R.id.buttonminus); 
    binto=(Button) findViewById(R.id.buttoninto); 
    bby=(Button) findViewById(R.id.buttonby); 
    bdot=(Button) findViewById(R.id.buttondot); 
    bclear=(Button) findViewById(R.id.buttonclear); 
    bequals=(Button) findViewById(R.id.buttonequals); 
    disp=(EditText) findViewById(R.id.disp_result); 

    b0.setOnClickListener(b0Listener); 
    b1.setOnClickListener(b1Listener); 
    b2.setOnClickListener(b2Listener); 
    b3.setOnClickListener(b3Listener); 
    b4.setOnClickListener(b4Listener); 
    b5.setOnClickListener(b5Listener); 
    b6.setOnClickListener(b6Listener); 
    b7.setOnClickListener(b7Listener); 
    b8.setOnClickListener(b8Listener); 
    b9.setOnClickListener(b9Listener); 
    bplus.setOnClickListener(bplusListener); 
    bminus.setOnClickListener(bminusListener); 
    binto.setOnClickListener(bintoListener); 
    bby.setOnClickListener(bbyListener); 
    bdot.setOnClickListener(bdotListener); 
    bclear.setOnClickListener(bclearListener); 
    bequals.setOnClickListener(bequalsListener); 
    } 
    private View.OnClickListener b0Listener = new View.OnClickListener() { 
     public void onClick(View v) { 
      disp.append("0"); 
     } 
    }; 
    private View.OnClickListener b1Listener = new View.OnClickListener() { 
     public void onClick(View v) { 
      disp.append("1"); 
     } 
    }; 
    private View.OnClickListener b2Listener = new View.OnClickListener() { 
     public void onClick(View v) { 
      disp.append("2"); 
     } 
    }; 
    private View.OnClickListener b3Listener = new View.OnClickListener() { 
     public void onClick(View v) { 
      disp.append("3"); 
     } 
    }; 
    private View.OnClickListener b4Listener = new View.OnClickListener() { 
     public void onClick(View v) { 
      disp.append("4"); 
     } 
    }; 
    private View.OnClickListener b5Listener = new View.OnClickListener() { 
     public void onClick(View v) { 
      disp.append("5"); 
     } 
    }; 
    private View.OnClickListener b6Listener = new View.OnClickListener() { 
     public void onClick(View v) { 
      disp.append("6"); 
     } 
    }; 
    private View.OnClickListener b7Listener = new View.OnClickListener() { 
     public void onClick(View v) { 
      disp.append("7"); 
     } 
    }; 
    private View.OnClickListener b8Listener = new View.OnClickListener() { 
     public void onClick(View v) { 
      disp.append("8"); 
     } 
    }; 
    private View.OnClickListener b9Listener = new View.OnClickListener() { 
     public void onClick(View v) { 
      disp.append("9"); 
     } 
    }; 
    private View.OnClickListener bplusListener = new View.OnClickListener() { 
     public void onClick(View v) { 
      if(disp.getText().toString().equals("")); 
      else if(state==1) { 
       op1=Float.parseFloat(disp.getText().toString()); 
       op='+'; 
       state++; 
       disp.setText(""); 
      } 
      else { 
       op2=Float.parseFloat(disp.getText().toString()); 
       op1=Float.parseFloat(perform(op,op1,op2)); 
       disp.setText(""); 
       op='+'; 
       state++; 
       decimalPoint=0; 
      } 
     } 
    }; 
    private View.OnClickListener bminusListener = new View.OnClickListener() { 
     public void onClick(View v) { 
      if(disp.getText().toString().equals("")); 
      else if(state==1) { 
       op1=Float.parseFloat(disp.getText().toString()); 
       op='-'; 
       state++; 
       disp.setText(""); 
      } 
      else { 
       op2=Float.parseFloat(disp.getText().toString()); 
       op1=Float.parseFloat(perform(op,op1,op2)); 
       disp.setText(""); 
       op='-'; 
       state++; 
       decimalPoint=0; 
      } 
     } 
    }; 
    private View.OnClickListener bintoListener = new View.OnClickListener() { 
     public void onClick(View v) { 
      if(disp.getText().toString().equals("")); 
      else if(state==1) { 
       op1=Float.parseFloat(disp.getText().toString()); 
       op='*'; 
       state++; 
       disp.setText(""); 
      } 
      else { 
       op2=Float.parseFloat(disp.getText().toString()); 
       op1=Float.parseFloat(perform(op,op1,op2)); 
       disp.setText(""); 
       op='*'; 
       state++; 
       decimalPoint=0; 
      } 
     } 
    }; 
    private View.OnClickListener bbyListener = new View.OnClickListener() { 
     public void onClick(View v) { 
      if(disp.getText().toString().equals("")); 
      else if(state==1) { 
       op1=Float.parseFloat(disp.getText().toString()); 
       op='/'; 
       state++; 
       disp.setText(""); 
      } 
      else { 
       op2=Float.parseFloat(disp.getText().toString()); 
       op1=Float.parseFloat(perform(op,op1,op2)); 
       disp.setText(""); 
       op='/'; 
       state++; 
       decimalPoint=0; 
      } 
     } 
    }; 
    private View.OnClickListener bdotListener = new View.OnClickListener() { 
     public void onClick(View v) { 
      if(!disp.getText().toString().equals("")) { 
       disp.append("."); 
       decimalPoint=1; 
      } 
     } 
    }; 
    private View.OnClickListener bclearListener = new View.OnClickListener() { 
     public void onClick(View v) { 
      op='\0'; 
      state=1; 
      disp.setText(""); 
      decimalPoint=0; 
     } 
    }; 
    private View.OnClickListener bequalsListener = new View.OnClickListener() { 
     public void onClick(View v) { 
      if(state!=1) { 
       op2=Float.parseFloat(disp.getText().toString()); 
       disp.setText(perform(op,op1,op2)); 
       op='\0'; 
       state=1; 
       decimalPoint=0; 
      } 
     } 
    }; 
    String perform(char op,float op1,float op2) { 
     switch(op) { 
      case '+' : return Float.toString(op1+op2); 
      case '-' : return Float.toString(op1-op2); 
      case '*' : return Float.toString(op1*op2); 
      case '/' : try { 
          return Float.toString(op1/op2); 
         } 
         catch(ArithmeticException e) { 
          return "Division by zero error..."; 
         } 
     } 
     return null; 
    } 
} 

这是一款Android的Java程序，它exaclty你想要的。您可以轻松地在您的Java程序中实现逻辑。