程序下来链接：http://pan.baidu.com/s/1slvI4f7

主程序：

“`
package com.example;

import com.example.R.id;

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

//import android.view.View.OnClickListener;

public class MainActivity extends Activity implements View.OnClickListener {
private Button add; //按钮+
private Button subtract; //按钮-
private Button multiply; //按钮*
private Button divide; //按钮/
private Button equal; //按钮=
private Button delete; //按钮删除一个输入的符号
private Button clear; //按钮用来清除输入框
private Button point; //按钮小数点

private Button one;         //按钮1
private Button two;
private Button three;private Button four;
private Button five;
private Button six;private Button seven;
private Button eight;
private Button nine;
private Button zero;private EditText showtext;//用来显示输入的符号和数字private String OperateSum="";//字符串用来保存输入的数字和符号
private char Operator;      //用来记录运算符号
private double num1=0,num2=0,sum=0;     //num1,num2记录输入的数字，sum保存运算的结果
//private boolean NewCalculate=true;
@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);initView();//对按钮和事件进行初始化
}
private void initView()
{one=(Button) findViewById(R.id.one);two=(Button) findViewById(R.id.two);three=(Button) findViewById(R.id.three);four=(Button) findViewById(R.id.four);five=(Button) findViewById(R.id.five);six=(Button) findViewById(R.id.six);seven=(Button) findViewById(R.id.seven);eight=(Button) findViewById(R.id.eight);nine=(Button) findViewById(R.id.nine);zero=(Button) findViewById(R.id.zero);add=(Button) findViewById(R.id.plus);subtract=(Button) findViewById(R.id.减号);multiply=(Button) findViewById(R.id.乘号);divide=(Button) findViewById(R.id.除号);delete=(Button) findViewById(R.id.删除);clear=(Button) findViewById(R.id.clear);equal=(Button) findViewById(R.id.equal);point=(Button) findViewById(R.id.point);//about=(Button) findViewById(R.id.about);showtext=(EditText) findViewById(R.id.text);showtext.setCursorVisible(false);zero.setOnClickListener(this);//添加按钮事件one.setOnClickListener(this);two.setOnClickListener(this);three.setOnClickListener(this);four.setOnClickListener(this);five.setOnClickListener(this);six.setOnClickListener(this);seven.setOnClickListener(this);eight.setOnClickListener(this);nine.setOnClickListener(this);add.setOnClickListener(this);subtract.setOnClickListener(this);multiply.setOnClickListener(this);divide.setOnClickListener(this);equal.setOnClickListener(this);delete.setOnClickListener(this);clear.setOnClickListener(this);point.setOnClickListener(this);//about.setOnClickListener(this);showtext.setOnClickListener(this);}private Button findViewById(Class<id> class1) {// TODO Auto-generated method stubreturn null;
}
@Override
public void onClick(View v) {switch (v.getId()) {case R.id.one:      //记录输入的数字1OperateSum=AddSum('1');//把数字添加进OperateSumshowtext.setText(OperateSum);   //把输入的数字显示在EditTextbreak;case R.id.two:      //记录输入的数字2OperateSum=AddSum('2');showtext.setText(OperateSum);break;case R.id.three:OperateSum=AddSum('3');showtext.setText(OperateSum);break;case R.id.four:OperateSum=AddSum('4');showtext.setText(OperateSum);break;case R.id.five:OperateSum=AddSum('5');showtext.setText(OperateSum);break;case R.id.six:OperateSum=AddSum('6');showtext.setText(OperateSum);break;case R.id.seven:OperateSum=AddSum('7');showtext.setText(OperateSum);break;case R.id.eight:OperateSum=AddSum('8');showtext.setText(OperateSum);break;case R.id.nine:OperateSum=AddSum('9');showtext.setText(OperateSum);break;case R.id.zero:OperateSum=AddSum('0');showtext.setText(OperateSum);break;case R.id.plus:      //记录+号OperateSum=AddSum('+');Operator='+';       //记录加法showtext.setText(OperateSum);   //把输入的+号显示在EditTextbreak;case R.id.减号:OperateSum=AddSum('-');Operator='-';showtext.setText(OperateSum);break;case R.id.乘号:OperateSum=AddSum('*');Operator='*';showtext.setText(OperateSum);break;case R.id.除号:OperateSum=AddSum('/');Operator='/';showtext.setText(OperateSum);break;case R.id.point:OperateSum=AddSum('.');showtext.setText(OperateSum);break;case R.id.删除:       //删除刚刚输入的一个符号if(OperateSum.length()>=1)//当至少已经输入了一个符号才执行{OperateSum=OperateSum.substring(0,OperateSum.length()-1);}showtext.setText(OperateSum);break;case R.id.clear:        //清除整个显示框OperateSum="";      //变量全部初始化num1=0;num2=0;sum=0;Operator=' ';showtext.setText(OperateSum);break;case R.id.equal:if(CheckInput(OperateSum))//当输入的数字和运算符都正确，才进行计算{OperateSum=OperateSum+"="+String.valueOf(equals(OperateSum));showtext.setText(OperateSum);//显示数字运算符和结果OperateSum=String.valueOf(sum); //保存运算结果，以便再直接输入一个运算符和一个数字进行下一次运算}else                        //输入不合理弹出警告{Toast.makeText(this,"Error", Toast.LENGTH_SHORT).show();}break;default:break;}
}
public String AddSum(char c)//添加并记录一个输入的数字或符号
{OperateSum=OperateSum+String.valueOf(c);return OperateSum;
}public boolean CheckInput(String OperateSum)    //这个方法用来检查用户输入的数字是否合理，比如用户输入了"9/3"这是合理的，加入输入了 " 8/*",这部合理
{if(OperateSum.length()<=2)//至少要分别输入了一个数字和一个运算符和一个数字，输入长度<=2肯定不合理，如输入 99 按下=按钮肯定不计算{return false;}if(OperateSum.indexOf(Operator, 1)==-1)     //如果没有输入运算符，肯定不合理{return false;}if(OperateSum.endsWith(String.valueOf(Operator)))       //最后以运算符结尾而不是数字，肯定不合理 如输入 9** ，不进行计算{return false;}return true;
}
public double equals(String OperateSum)         //计算结果
{int indexOfOperator=0;indexOfOperator=OperateSum.indexOf(Operator,1);         //计算运算符在从输入的OperateSum字符串里的位置if(OperateSum.length()>=3){num1=Double.parseDouble(OperateSum.substring(0, indexOfOperator));  //从输入的OperateSum字符串里得到第一个运算数num2=Double.parseDouble(OperateSum.substring(indexOfOperator + 1, OperateSum.length()));    //从输入的OperateSum字符串里得到第二个运算数}switch (Operator)       //根据运算符进行计算{case '+':           //加法运算sum=num1+num2;break;case '-':           //减法运算sum=num1-num2;break;case '*':           //乘法运算sum=num1*num2;break;case '/':           //除法运算if(num2!=0)     //除数不应该为0{sum=num1/num2;}else{sum=0;Toast.makeText(this,"Error", Toast.LENGTH_LONG).show();//若除数是0，弹出警告}break;default:break;}return sum;         //返回结果
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.menu, menu);return true;
}@Override
public boolean onOptionsItemSelected(MenuItem item) {// Handle action bar item clicks here. The action bar will// automatically handle clicks on the Home/Up button, so long// as you specify a parent activity in AndroidManifest.xml.int id = item.getItemId();//noinspection SimplifiableIfStatementif (id == R.id.action_settings) {return true;}return super.onOptionsItemSelected(item);
}

}

//机智勇敢的李小白“`

layout：