android studio实现简单的计算器功能

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:app="http://schemas.android.com/apk/res-auto"
 xmlns:tools="http://schemas.android.com/tools"
 android:id="@+id/next"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 app:layout_behavior="@string/appbar_scrolling_view_behavior"
 tools:context=".MainActivity"
 tools:showIn="@layout/activity_main">

 <!--<TextView-->
  <!--android:layout_width="wrap_content"-->
  <!--android:layout_height="wrap_content"-->
  <!--android:text="Hello World!"-->
  <!--app:layout_constraintBottom_toBottomOf="parent"-->
  <!--app:layout_constraintLeft_toLeftOf="parent"-->
  <!--app:layout_constraintRight_toRightOf="parent"-->
  <!--app:layout_constraintTop_toTopOf="parent" />-->


 <LinearLayout
  android:layout_width="fill_parent"
  android:layout_height="match_parent"
  android:orientation="vertical" >


 <EditText
  android:id="@+id/input"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:layout_gravity="center"
  android:editable="false"
  android:hint="@string/shuru" />

 <EditText
  android:id="@+id/output"
  android:layout_width="match_parent"
  android:layout_height="70dp"
  android:layout_gravity="center"
  android:editable="true"
  android:gravity="right"
  android:hint="@string/shuchu" />

 <RelativeLayout
  android:layout_width="350dp"
  android:layout_height="wrap_content"
  android:layout_gravity="center">

  <Button
   android:id="@+id/clear"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentLeft="true"
   android:text="@string/clear"
   android:textSize="40sp" />

  <Button
   android:id="@+id/back"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_toRightOf="@id/clear"
   android:text="@string/back"
   android:textSize="40sp" />

  <Button
   android:id="@+id/divide"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_toRightOf="@id/back"
   android:text="@string/divide"
   android:textSize="40sp" />

  <Button
   android:id="@+id/multiply"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_toRightOf="@id/divide"
   android:text="@string/multiply"
   android:textSize="40sp" />

  <Button
   android:id="@+id/seven"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentLeft="true"
   android:layout_below="@id/clear"
   android:text="@string/seven"
   android:textSize="40sp" />

  <Button
   android:id="@+id/eight"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_toRightOf="@id/seven"
   android:layout_below="@id/divide"
   android:text="@string/eight"
   android:textSize="40sp" />

  <Button
   android:id="@+id/nine"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_below="@id/multiply"
   android:layout_toRightOf="@id/eight"
   android:text="@string/nine"
   android:textSize="40sp" />

  <Button
   android:id="@+id/subtract"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentRight="true"
   android:layout_below="@id/multiply"
   android:layout_toRightOf="@id/nine"
   android:text="@string/subtract"
   android:textSize="40sp" />

  <Button
   android:id="@+id/four"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentLeft="true"
   android:layout_below="@id/seven"
   android:text="@string/four"
   android:textSize="40sp" />

  <Button
   android:id="@+id/five"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_below="@id/eight"
   android:layout_toRightOf="@id/four"
   android:text="@string/five"
   android:textSize="40sp" />

  <Button
   android:id="@+id/six"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_below="@id/nine"
   android:layout_toRightOf="@id/five"
   android:text="@string/six"
   android:textSize="40sp" />

  <Button
   android:id="@+id/add"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentRight="true"
   android:layout_below="@id/subtract"
   android:layout_toRightOf="@id/six"
   android:text="@string/add"
   android:textSize="40sp" />

  <Button
   android:id="@+id/one"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentLeft="true"

   android:layout_below="@id/four"
   android:text="@string/one"
   android:textSize="40sp" />

  <Button
   android:id="@+id/two"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_below="@id/five"
   android:layout_toRightOf="@id/one"
   android:text="@string/two"
   android:textSize="40sp" />

  <Button
   android:id="@+id/three"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_below="@id/six"
   android:layout_toRightOf="@id/two"
   android:text="@string/three"
   android:textSize="40sp" />

  <Button
   android:id="@+id/result"
   android:layout_width="wrap_content"
   android:layout_height="146dp"
   android:layout_alignParentRight="true"
   android:layout_below="@id/add"
   android:layout_toRightOf="@id/three"
   android:text="@string/result"
   android:textSize="40sp" />


  <Button
   android:id="@+id/zero"
   android:layout_width="175dp"
   android:layout_height="wrap_content"
   android:layout_alignParentLeft="true"
   android:layout_below="@id/one"
   android:text="@string/zero"
   android:textSize="40sp" />

  <Button
   android:id="@+id/dot"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_below="@id/three"
   android:layout_toRightOf="@id/zero"
   android:text="@string/dot"
   android:textSize="40sp" />

 </RelativeLayout>

 </LinearLayout>


</android.support.constraint.ConstraintLayout>

<resources>
 <string name="app_name">Calculator</string>
 <string name="action_settings">Settings</string>
 <string name="title_activity_page2">page2</string>

 <string name="next">下一页</string>
 <string name="zero">0</string>
 <string name="one">1</string>
 <string name="two">2</string>
 <string name="three">3</string>
 <string name="four">4</string>
 <string name="five">5</string>
 <string name="six">6</string>
 <string name="seven">7</string>
 <string name="eight">8</string>
 <string name="nine">9</string>
 <string name="add">+</string>
 <string name="subtract">-</string>
 <string name="multiply">*</string>
 <string name="divide">/</string>
 <string name="clear">CE</string>
 <string name="back">&#60;-</string>
 <string name="result">=</string>
 <string name="shuru">请输入：</string>
 <string name="shuchu">结果:</string>
 <string name="dot">.</string>
 <string name="resultText">计算式</string>

</resources>

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<str1.length();){
     int count =1;
     a:for(int j =i+1;j<str1.length();j++){
      char c =str1.charAt(j);
      if(c=="*"||c=="/"){
       break a;
      }else{
       count++;
      }
     }

     //将数字截取出来
     String s2 =str1.substring(i,i+count);
     double d = Double.parseDouble(s2);
     if(i==0){
      total = d;
     }else{
      char c1 = str1.charAt(i-1);
      if(c1=="*"){
       total*=d;
      }else if(c1=="/"){
       //如果除数为0，直接返回null;
       if(d == 0)
        return null;
       total/=d;
      }
     }
     i+=count+1;
    }
    s= s.replace(str1, total+"");
   }
  }
  //进行加减运算
  for(int i =0;i<s.length();i++){
   int count =1;
   a:for(int j=i+1;j<s.length();j++){
    char c = s.charAt(j);
    if(c=="+"||c=="-"){
     break a;
    }else{
     count++;
    }
   }
   String s3= s.substring(i,i+count);
   double d2 = Double.parseDouble(s3);
   if(i==0){
    total1 = d2;
   }else{
    char c = s.charAt(i-1);
    if(c=="+"){
     total1+=d2;
    }else if(c=="-"){
     total1-=d2;
    }
   }
   i+=count;
  }
  return total1;
 }

}