引言：

　　我的android计算器的实现方式是：按钮输入一次，就处理一次。

　　但是如果你学过数据结构（栈），就可以使用表达式解析（前缀，后缀）处理。

　　而这个方式已经很成熟了，但是时间有限，只完成了这个简单的计算器。

　　至于，这个Android的布局已经在我博客中发布了，不再讲述。　　　　
复制代码 代码如下:
package com.example.androidlessontwo;

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

public class MainActivity extends Activity {

private Button[] buttonNum=new Button[11];
private Button[] buttonComand=new Button[5];
private TextView input=null;
private TextView rl=null;
private Button buttonClear=null;
private boolean firstFlag=true;
private double result=0.0;
private String lastCommand;

public void MyCalculator()
{
result = 0.0;
firstFlag=true;
lastCommand="=";
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
buttonNum[0]=(Button) findViewById(R.id.num0);
buttonNum[1]=(Button) findViewById(R.id.num1);
buttonNum[2]=(Button) findViewById(R.id.num2);
buttonNum[3]=(Button) findViewById(R.id.num3);
buttonNum[4]=(Button) findViewById(R.id.num4);
buttonNum[5]=(Button) findViewById(R.id.num5);
buttonNum[6]=(Button) findViewById(R.id.num6);
buttonNum[7]=(Button) findViewById(R.id.num7);
buttonNum[8]=(Button) findViewById(R.id.num8);
buttonNum[9]=(Button) findViewById(R.id.num9);
buttonNum[10]=(Button) findViewById(R.id.point);

buttonComand[0]=(Button) findViewById(R.id.add);
buttonComand[1]=(Button) findViewById(R.id.sub);
buttonComand[2]=(Button) findViewById(R.id.ride);
buttonComand[3]=(Button) findViewById(R.id.divide);
buttonComand[4]=(Button) findViewById(R.id.equal);

input=(TextView) findViewById(R.id.input);
rl =(TextView) findViewById(R.id.rl);
buttonClear=(Button) findViewById(R.id.clean);

NumberAction na= new NumberAction();
CommandAction ca=new CommandAction();
for(Button bc:buttonComand)
{
bc.setOnClickListener(ca);
}
for(Button bc:buttonNum)
{
bc.setOnClickListener(na);
}
buttonClear.setOnClickListener(new Button.OnClickListener()
{

@Override
public void onClick(View v) {
MyCalculator();
rl.setText("0.0");
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
private class NumberAction implements Button.OnClickListener
{

@Override
public void onClick(View view)
{
Button btn = (Button)view;
String inputTemp =btn.getText().toString();//6
input.setText(input.getText().toString()+inputTemp);
double numtemp = 0;
switch(btn.getId())
{
case R.id.num0:
{
if(firstFlag)
{
result=result*10+0;
firstFlag=false;
}
else
numtemp=numtemp*10+0;
break;
}
case R.id.num1:
{
if(firstFlag)
{
result=result*10+1;
firstFlag=false;
}
else
numtemp=numtemp*10+1;
break;
}
case R.id.num2:
{
if(firstFlag)
{
result=result*10+2;
firstFlag=false;
}
else
numtemp=numtemp*10+2;
break;
}
case R.id.num3:
{
if(firstFlag)
{
result=result*10+3;
firstFlag=false;
}
else
numtemp=numtemp*10+3;
break;
}
case R.id.num4:
{
if(firstFlag)
{
result=result*10+4;
firstFlag=false;
}
else
numtemp=numtemp*10+4;
break;
}
case R.id.num5:
{
if(firstFlag)
{
result=result*10+5;
firstFlag=false;
}
else
numtemp=numtemp*10+5;
break;
}
case R.id.num6:
{
if(firstFlag)
{
result=result*10+6;
firstFlag=false;
}
else
{
numtemp=numtemp*10+6;
calculate(numtemp);
}
break;
}
case R.id.num7:
{
if(firstFlag)
{
result=result*10+7;
firstFlag=false;
}
else
{
numtemp=numtemp*10+7;
calculate(numtemp);
}
break;
}
case R.id.num8:
{
if(firstFlag)
{
result=result*10+8;
{
result=result*10+8;
firstFlag=false;
}
}
else
{
numtemp=numtemp*10+8;
calculate(numtemp);
}
break;
}
case R.id.num9:
{
if(firstFlag)
{
result=result*10+9;
firstFlag=false;
}
else
{
numtemp=numtemp*10+9;
calculate(numtemp);
}
break;
}
}




}

}

private class CommandAction implements Button.OnClickListener
{
@Override
public void onClick(View v)
{
Button btn=(Button)v;
String inputCommand=(String)btn.getText();
switch(btn.getId())
{
case R.id.add:
{
lastCommand="+";
break;
}
case R.id.sub:
{
lastCommand="-";
break;
}
case R.id.ride:
{
lastCommand="*";
break;
}
case R.id.divide:
{
lastCommand="/";
break;
}
case R.id.equal:
{
lastCommand="=";
input.setText("");
rl.setText(String.valueOf(result));
return ;
}

}
input.setText(input.getText()+inputCommand);
}

}
private void calculate(double x)
{


if(lastCommand.equals("+"))
{
result += x;
}

if(lastCommand.equals("-"))
{
result -= x;
}

if(lastCommand.equals("*"))
{
result *= x;
}

if(lastCommand.equals("/"))
{
result /= x;
}
}

}