【Android】编写一个简易计算机

1.界面

2.源代码

activity_main.xml

    
    
        //第一列
        
            
        
        //第二行
        
            
            
            
            
        
        //第三行
        
            
            
            
            
        
        
            
            
            
            
        
        
            
            
            
            
        
    

MainActivity.java

package com.example.tanjy.ex2_9_1;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.util.regex.Pattern;

public class MainActivity extends AppCompatActivity {
    private Button bt_num0,bt_num1,bt_num2,bt_num3,bt_num4,bt_num5,bt_num6,bt_num7,bt_num8,bt_num9,bt_clear,bt_div,bt_mult,bt_minus,bt_plus,bt_equal,bt_dot;
    private TextView et_calc;
    private String progress,currentSymbol;  //currentSymbol用来记录当前使用的运算符

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initViewAndListener();
    }
    private void initViewAndListener() {
        bt_num0=(Button)findViewById(R.id.bt_num0);
        bt_num0.setOnClickListener(new clickNum());
        bt_num1=(Button)findViewById(R.id.bt_num1);
        bt_num1.setOnClickListener(new clickNum());
        bt_num2=(Button)findViewById(R.id.bt_num2);
        bt_num2.setOnClickListener(new clickNum());
        bt_num3=(Button)findViewById(R.id.bt_num3);
        bt_num3.setOnClickListener(new clickNum());
        bt_num4=(Button)findViewById(R.id.bt_num4);
        bt_num4.setOnClickListener(new clickNum());
        bt_num5=(Button)findViewById(R.id.bt_num5);
        bt_num5.setOnClickListener(new clickNum());
        bt_num6=(Button)findViewById(R.id.bt_num6);
        bt_num6.setOnClickListener(new clickNum());
        bt_num7=(Button)findViewById(R.id.bt_num7);
        bt_num7.setOnClickListener(new clickNum());
        bt_num8=(Button)findViewById(R.id.bt_num8);
        bt_num8.setOnClickListener(new clickNum());
        bt_num9=(Button)findViewById(R.id.bt_num9);
        bt_num9.setOnClickListener(new clickNum());

        bt_clear=(Button)findViewById(R.id.bt_clear);
        bt_clear.setOnClickListener(new clickOther());
        bt_div=(Button)findViewById(R.id.bt_div);
        bt_div.setOnClickListener(new clickOther());
        bt_mult=(Button)findViewById(R.id.bt_mult);
        bt_mult.setOnClickListener(new clickOther());
        bt_minus=(Button)findViewById(R.id.bt_minus);
        bt_minus.setOnClickListener(new clickOther());
        bt_plus=(Button)findViewById(R.id.bt_plus);
        bt_plus.setOnClickListener(new clickOther());
        bt_equal=(Button)findViewById(R.id.bt_equal);
        bt_equal.setOnClickListener(new clickOther());
        bt_dot=(Button)findViewById(R.id.bt_dot);
        bt_dot.setOnClickListener(new clickOther());

        et_calc=(TextView)findViewById(R.id.et_calc);

    }

    //数字按钮监听器
    class clickNum implements View.OnClickListener{
        public void onClick(View v) {
            Button num = (Button) v;                     //获取用户点击的按钮对象
            String clickNum = num.getText().toString();  //获取用户点击的数字
            progress = et_calc.getText().toString();     //获取结果的值并赋值给progress
            if(v == bt_num0){          //按0
                progress = dealRes(progress,clickNum);
            }else {                 //按1-9
                progress = dealRes(progress,clickNum);
            }
            et_calc.setText(progress);
        }
    }
    //功能按钮监听器，可以加“.”的情况
    class clickOther implements View.OnClickListener {
        public void onClick(View v) {
            Button num = (Button) v;
            String reg = "^(\\d+)|^(\\d+\\+|-|/|\\*\\d+)|^(\\d+\\.\\d+\\+|-|/|\\*\\d+)";
            String symbol = num.getText().toString();    //获取用户点击的符号
            progress = et_calc.getText().toString();     //获取结果的值并赋值给progress
            //按清除按钮
            if (v == bt_clear) {
                progress = "0";
                currentSymbol = "";
                //按等号按钮
            } else if (v == bt_equal) {
                String[] arr = progress.split("\\+|-|/|\\*");
                if (progress.split("\\+|-|/|\\*").length != 1) {
                    progress = splitStr(progress, currentSymbol);
                }
                //按“.”按钮
            } else if (v == bt_dot) {
                //如果不符合可以加“.”的情况，则不变，否则加上“.”
                progress = !Pattern.matches(reg, progress) ? progress : dealRes(progress, symbol);
                //按加减乘除按钮
            } else {
                //如果式子中存在“+*/”，进行运算；如果存在“-”且不是首位，进行运算
                Boolean a = progress.indexOf('+') != -1 || progress.indexOf('*') != -1 || progress.indexOf('/') != -1;
                Boolean b = progress.indexOf('-') != -1;
                Boolean c = progress.lastIndexOf('-') != 0;
                if (a) {
                    progress = splitStr(progress, currentSymbol);
                    currentSymbol = num.getText().toString();
                    progress = progress + currentSymbol;
                } else if (b && c) {
                    progress = splitStr(progress, currentSymbol);
                    currentSymbol = num.getText().toString();
                    progress = progress + currentSymbol;
                } else {
                    currentSymbol = num.getText().toString();
                    progress = progress + currentSymbol;
                }
            }
            et_calc.setText(progress);
        }
    }
    //分割字符串，进行计算，并返回计算结果
    public String splitStr (String str , String calSymbol) {
        String []strArray = new String[20];
        strArray = str.split("\\+|-|/|\\*");         //使用+-*/对式子进行分割
        Double res = 0.0;
        switch (calSymbol) {                                //根据运算符号选取操作
            case "+" : {
                if (strArray.length > 2) res = (- Double.parseDouble(strArray[1])) + Double.parseDouble(strArray[2]);
                else res = Double.parseDouble(strArray[0]) + Double.parseDouble(strArray[1]);
                currentSymbol = "";
                break;
            }
            case "-" : {
                if (strArray.length > 2) res = (- Double.parseDouble(strArray[1])) - Double.parseDouble(strArray[2]);
                else  res = str.indexOf('-') == 0 ? Double.parseDouble(str) : Double.parseDouble(strArray[0]) - Double.parseDouble(strArray[1]);
                currentSymbol = "";
                break;
            }
            case "*" : {
                if (strArray.length > 2) res = (- Double.parseDouble(strArray[1])) * Double.parseDouble(strArray[2]);
                else res = Double.parseDouble(strArray[0]) * Double.parseDouble(strArray[1]);
                currentSymbol = "";
                break;
            }
            case "/" : {
                if (strArray.length > 2) res = (- Double.parseDouble(strArray[1])) / Double.parseDouble(strArray[2]);
                else res = Double.parseDouble(strArray[0]) / Double.parseDouble(strArray[1]);
                currentSymbol = "";
                break;
            }
        }
        return String.valueOf(res);
    }
    //判读字符串的组成，并返回结果
    public String dealRes (String str,String clickSymbol){
        String reValue = "";
        //如果字符串长度为0，直接返回点击的字符
        if (str.length() == 0) {
            reValue = clickSymbol;
            //如果字符串长度为为1，且等于0，且字符不为“.”，则返回点击的字符
        } else if(str.length() == 1 && Integer.parseInt(str) == 0 && clickSymbol != bt_dot.getText().toString()) {
            reValue = clickSymbol ;
            //其他情况，直接拼接点击的字符字符
        } else {
            reValue = str + clickSymbol;
        }
        return  reValue;
    }

}

3.运行结果

按2*3

再按“=”按钮

说明：本文参考链接：https://blog.csdn.net/qq_40121804/article/details/88607188