用android studio写一个简单的计算器
先来个效果图：
功能： 满足加减乘除四则运算规则，有回退、清除功能。
下面的代码只是完成基本功能，若添加背景图请看Android Studio App设置背景图片
content_main.xml文件（页面布局，content_main.xml代码包含在activity_main.xml文件中）：
strings.xml（content_main.xml代码中的一些变量在此代码中定义的）：
Calculator
Settings
page2
下一页
0
1
2
3
4
5
6
7
8
9
+
-
*
/
CE
<-
=
请输入：
结果:
.
计算式
MainActivity.Java（计算器中实现计算功能的核心代码）：
package com.example.dell.calculator;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.app.Activity;
import android.content.Context;
import android.view.View.OnClickListener;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Button;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainActivity extends AppCompatActivity {
private EditText output = null;
private EditText input = null;
private Button btn0 = null;
private Button btn1 = null;
private Button btn2 = null;
private Button btn3 = null;
private Button btn4 = null;
private Button btn5 = null;
private Button btn6 = null;
private Button btn7 = null;
private Button btn8 = null;
private Button btn9 = null;
private Button btnadd = null;
private Button btnsubtract = null;
private Button btnmultiply = null;
private Button btndivide = null;
private Button btnclear = null;
private Button btnback = null;
private Button btndot = null;
private Button btnresult = null;
private String text = "";//保存输入的数字和符号
private Double result = 0.0;//输出结果
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
output = (EditText) findViewById(R.id.output);
input = (EditText) findViewById(R.id.input);
btn0 = (Button) findViewById(R.id.zero);
btn1 = (Button) findViewById(R.id.one);
btn2 = (Button) findViewById(R.id.two);
btn3 = (Button) findViewById(R.id.three);
btn4 = (Button) findViewById(R.id.four);
btn5 = (Button) findViewById(R.id.five);
btn6 = (Button) findViewById(R.id.six);
btn7 = (Button) findViewById(R.id.seven);
btn8 = (Button) findViewById(R.id.eight);
btn9 = (Button) findViewById(R.id.nine);
btnadd = (Button) findViewById(R.id.add);
btnsubtract = (Button) findViewById(R.id.subtract);
btnmultiply = (Button) findViewById(R.id.multiply);
btndivide = (Button) findViewById(R.id.divide);
btnclear = (Button) findViewById(R.id.clear);
btnback = (Button) findViewById(R.id.back);
btndot = (Button) findViewById(R.id.dot);
btnresult = (Button) findViewById(R.id.result);
//设置按钮侦听事件
btn0.setOnClickListener(listener);
btn1.setOnClickListener(listener);
btn2.setOnClickListener(listener);
btn3.setOnClickListener(listener);
btn4.setOnClickListener(listener);
btn5.setOnClickListener(listener);
btn6.setOnClickListener(listener);
btn7.setOnClickListener(listener);
btn8.setOnClickListener(listener);
btn9.setOnClickListener(listener);
btnadd.setOnClickListener(listener);
btnsubtract.setOnClickListener(listener);
btnmultiply.setOnClickListener(listener);
btndivide.setOnClickListener(listener);
btnclear.setOnClickListener(listener);
btnback.setOnClickListener(listener);
btndot.setOnClickListener(listener);
btnresult.setOnClickListener(listener);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
@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);
}
//public void onClickNext(View view) {
// Intent intent = new Intent(this,page2.class);
// startActivity(intent);
// }
private OnClickListener listener = new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
//输入数字
case R.id.zero:
num(0);
break;
case R.id.one:
num(1);
break;
case R.id.two:
num(2);
break;
case R.id.three:
num(3);
break;
case R.id.four:
num(4);
break;
case R.id.five:
num(5);
break;
case R.id.six:
num(6);
break;
case R.id.seven:
num(7);
break;
case R.id.eight:
num(8);
break;
case R.id.nine:
num(9);
break;
case R.id.dot:
dot();
break;
//执行运算
case R.id.add:
add();
break;
case R.id.subtract:
sub();
break;
case R.id.multiply:
multiply();
break;
case R.id.divide:
divide();
break;
case R.id.clear:
clear();
break;
case R.id.back:
back();
break;
//计算结果
case R.id.result:
result();
break;
default:
break;
}
input.setText(text);
output.setText(String.valueOf(result));
}
};
private void num(int i) {
// TODO Auto-generated method stub
text = text + String.valueOf(i);
}
private void dot() {
// TODO Auto-generated method stub
text = text + ".";
}
private void clear() {
// TODO Auto-generated method stub
text = "";
result = null;
input.setText("");
output.setText("");
}
private void back() {
// TODO Auto-generated method stub
String str = text.substring(0, text.length()-1);
text = str;
}
private void add() {
// TODO Auto-generated method stub
text += "+";
}
private void sub() {
// TODO Auto-generated method stub
text += "-";
}
private void multiply() {
// TODO Auto-generated method stub
text += "*";
}
private void divide() {
// TODO Auto-generated method stub
text += "/";
}
//计算输出结果
private void result() {
// TODO Auto-generated method stub
result = testOperation(text);
}
public Double testOperation(String s){
//分割字符然后放进数组
String s1 =s.replace("+","-");
String[] str = s1.split("-");
double total1=0;
//先遍历数组，把里面的乘除结果算出来
for(String str1:str){
if(str1.contains("*")||str1.contains("/")){
double total = 0;
for(int i =0;i