andriod简易计算器

1、功能概述

本程序请为Android手机开发的一个四则运算计算器，它能解析一个由“加减乘除”四种运算所构成的数学表达式，并计算出结果。支持运算符优先级；支持多重嵌套的括号；运行界面如下：

2、使用说明

通过键盘输入特的运算表达式，可以然后按“等于=”按钮，即可立即得到答案；按“清除”按钮即可将界面输入框中的内容全部清除。

3、核心类

本程序存在两个核心类，CaculateEx.class和MainActivity.class，其中CaculateEx.class用来进行复杂的计算操作，而MainActivity.class用来进行界面展示和结果的展示。

3.1、核心类（CaculateEx）

CaculateEx.class源代码以及说明如下：

package com.lsf.cal.calc;

 

importjava.util.Stack;

 

public class CaculateEx {

    public String suffix_expression(Stringexpression)//中缀表达式转换后缀表达式（逆波兰式）

    {

 

        //Stack<Double> s2=newStack<Double>();//存放数字栈

        Stack<Object> s3=new Stack<Object>();//存放结果栈

        Stack<Character> s4=new Stack<Character>();//存放操作符栈

        int len=expression.length();//

 

        char c1;

        doublenumber;

        int m,n=-1;

        for(inti=0;i<len;i++)

        {

            c1=expression.charAt(i);

            if(isOprator(c1)||(i==len-1))//如果是运算符，将前面的数数字入s3栈，操作符入s4栈

            {

                if(i==len-1&&(!isOprator(c1)))//当最后一位且不是操作符时，将前面的数压栈

                    m=i+1;

                else

                    m=i;

                //操作数入栈,向前遍历到下一个运算符，将中间的字符串转化为double

                for(intj=i-1;j>=0;j--)

                {

                    if(isOprator(expression.charAt(j)))

                    {

                        n=j;

                        break;

                    }

                    n=j-1;

                }

                if(m!=n+1)//只有当这两个值不等时中间才会有操作数

                {

                    number=Double.parseDouble(expression.substring(n+1,m));

                    s3.push(number);

                }

                //运算符入栈

                if(i==0&&(c1!='('))//当表达式第一个字符就为运算符且不是左括号时，返回表达式错误

                {

                    return"表达式错误！";

                }

                else if(isOprator(c1))//且是操作符时

                {

                    while(true)

                    {

                        if(s4.isEmpty()||s4.peek()=='('||c1=='(')//如果栈为空或者栈顶元素为（或者c1为（时，则直接将运算符压入栈内

                        {

                            s4.push(c1);

                            break;

                        }

                        elseif(c1==')')//当c1为）时，依次弹出s4中的运算符并压入s3，直到（，舍弃这一对括号

                        {

                            while(s4.peek()!='(')

                            {

                                s3.push(s4.pop());

                                if(s4.isEmpty())//弹出所有不为左括号之后堆栈为空，则表达式不合法

                                {

                                    return"缺少左括号";

                                }

                            }

                            s4.pop();//弹出（

                            break;

                        }

                        else

                        {

                            if(priorityCompare(c1,s4.peek())==1)//判断优先级，优先级高入栈，优先级低将栈顶运算符压入s3

                            {

                                s4.push(c1);

                                break;

                            }

                            else

                            {

                                s3.push(s4.pop());

                            }

                        }

                    }

                }

            }

            else

                continue;

 

        }

        while(!s4.isEmpty())//表达式结束后，依次将s4剩下的运算符压入s3

        {

            if((char)s4.peek()=='(')

                return"缺少右括号";

            s3.push(s4.pop());

        }

        return count_result(s3);

    }

    private int priorityCompare(charc1,charc2)

    {

        switch(c1)

        {

            case'+':

            case'-':

                return (c2 =='*' || c2 =='/' ? -1 : 0);

            case'*':

            case'/':

                return (c2 =='+' || c2 =='-' ? 1 : 0);

        }

        return 1;

    }

    //判断字符是否为运算符，是为真，不是为假

    private boolean isOprator(Object c) {

        // TODO Auto-generated method stub

        try

        {

            charc1=(char)c;

            if(c1=='+'||c1=='-'||c1=='*'||c1=='/'||c1=='('||c1==')')

                returntrue;

 

        }

        catch (Exceptione) {

            // TODO: handle exception

            return false;

        }

        return false;

    }

    private String count_result(Stack<Object>ob) {

        // TODO Auto-generated method stub

        Stack<Object> s1=new Stack<Object>();//后缀表达式栈

        Stack<Double> s2=new Stack<Double>();//操作数栈

        //char c1;

        //   Stack<Character> s3=new Stack<Character>();//操作符栈

 

        while(!ob.isEmpty())//将传入的栈逆序压入

        {

            s1.push(ob.pop());

        }

        while(!s1.isEmpty())

        {

            if(!isOprator(s1.peek()))//遇到非操作符，压入s2栈

            {

                s2.push((Double)s1.pop());

            }

            else

            {

                s2.push(cout(s2.pop(),s2.pop(),(char)s1.pop()));

            }

        }

        return Double.toString(s2.peek());

 

    }

 

    private Double cout(doubles1,doubles2,chars3)

    {

        doubleresult=0;

        switch(s3)

        {

            case'+':

                result=s1+s2;

                break;

            case'-':

                result=s1-s2;

                break;

            case'*':

                result=s1*s2;

                break;

            case'/':

                result=s1/s2;

                break;

        }

        returnresult;

    }

}

3.2、核心类（MainActivity）

MainActivity.class源代码如下：

 

4、运package com.lsf.cal.calc;

 

importandroid.support.v7.app.ActionBarActivity;

importandroid.os.Bundle;

importandroid.view.Menu;

importandroid.view.MenuItem;

importandroid.view.View;

importandroid.widget.Button;

importandroid.widget.EditText;

 

 

public class MainActivity extends ActionBarActivityimplements View.OnClickListener {

 

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        Button caculateButton=(Button)findViewById(R.id.button);

        caculateButton.setOnClickListener(this);

        Button clearButton=(Button)findViewById(R.id.clear);

        clearButton.setOnClickListener(this);

    }

    @Override

    public void onClick(View v) {

        EditText editText = (EditText) findViewById(R.id.text);

        if(v.getId()==R.id.button) {

            CaculateEx caculateEx =new CaculateEx();

            String expreString =editText.getText().toString();

            expreString = caculateEx.suffix_expression(expreString);

            editText.setText(expreString);

        }else{

            editText.setText("");

        }

    }

 

 

    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to theaction bar if it is present.

        getMenuInflater().inflate(R.menu.menu_main,menu);

        return true;

    }

 

    @Override

    public boolean onOptionsItemSelected(MenuItem item) {

        // Handle action bar item clicks here. Theaction bar will

        // automatically handle clicks on theHome/Up button, so long

        // as you specify a parent activity inAndroidManifest.xml.

        int id = item.getItemId();

 

        //noinspectionSimplifiableIfStatement

        if (id == R.id.action_settings) {

            return true;

        }

 

        return super.onOptionsItemSelected(item);

    }

 

 

}