Android 一个简单的计算器APP
apk下载地址：
http://pan.baidu.com/s/1dD3513j
MainActivity.java文件内容：
package netpythontojavaviewmodecontents.csdn.blog.calculator0;
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.add);
subtract=(Button) findViewById(R.id.subtract);
multiply=(Button) findViewById(R.id.multiply);
divide=(Button) findViewById(R.id.divide);
delete=(Button) findViewById(R.id.delete);
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);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.one: //记录输入的数字1
OperateSum=AddSum('1');//把数字添加进OperateSum
showtext.setText(OperateSum); //把输入的数字显示在EditText
break;
case R.id.two: //记录输入的数字2
OperateSum=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.add: //记录+号
OperateSum=AddSum('+');
Operator='+'; //记录加法
showtext.setText(OperateSum); //把输入的+号显示在EditText
break;
case R.id.subtract:
OperateSum=AddSum('-');
Operator='-';
showtext.setText(OperateSum);
break;
case R.id.multiply:
OperateSum=AddSum('*');
Operator='*';
showtext.setText(OperateSum);
break;
case R.id.divide:
OperateSum=AddSum('/');
Operator='/';
showtext.setText(OperateSum);
break;
case R.id.point:
OperateSum=AddSum('.');
showtext.setText(OperateSum);
break;
case R.id.delete: //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_main, 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 SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
/>
