<?xml version="1.0" encoding="utf-8"?>
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical"
 android:background="@drawable/jsj1">
 <textview
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:text="计算器"
  android:textsize="20dp"
  android:gravity="center"
  android:textcolor="#ee4000"/>
 <textview
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:text="输入数字"/>
 <edittext
  android:id="@+id/et001"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"/>
 <textview
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:text="运算结果"/>
 <edittext
  android:id="@+id/et002"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"/>
 <linearlayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal">
  <button
   android:layout_marginleft="5dp"
   android:id="@+id/btn001"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="c"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/qqqqqqqqqq"/>
  <button
   android:id="@+id/btn002"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="÷"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/qqqqqqqqqq"/>

  <button
   android:id="@+id/btn003"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="×"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/qqqqqqqqqq"/>
  <button
   android:id="@+id/btn004"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="cx"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/qqqqqqqqqq"/>

 </linearlayout>
 <linearlayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal">
  <button
   android:layout_marginleft="5dp"
   android:id="@+id/btn005"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="7"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/sssssssssssssss"/>
  <button
   android:id="@+id/btn006"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="8"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/sssssssssssssss"/>
  <button
   android:id="@+id/btn007"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="9"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/sssssssssssssss"/>
  <button
   android:id="@+id/btn008"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="-"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/qqqqqqqqqq"/>

 </linearlayout>
 <linearlayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal">
  <button
   android:layout_marginleft="5dp"
   android:id="@+id/btn009"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="4"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/sssssssssssssss"/>
  <button
   android:id="@+id/btn0010"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="5"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/sssssssssssssss"/>
  <button
   android:id="@+id/btn0011"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="6"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/sssssssssssssss"/>
  <button
   android:id="@+id/btn0012"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="+"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/qqqqqqqqqq"/>

 </linearlayout>
 <linearlayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal">
  <button
   android:layout_marginleft="5dp"
   android:id="@+id/btn0013"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="1"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/sssssssssssssss"/>
  <button
   android:id="@+id/btn0014"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="2"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/sssssssssssssss"/>
  <button
   android:id="@+id/btn0015"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="3"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/sssssssssssssss"/>
  <button
   android:id="@+id/btn0019"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="."
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/qqqqqqqqqq"/>

 </linearlayout>

 <linearlayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal">
  <button
   android:layout_marginleft="5dp"
   android:id="@+id/btn0018"
   android:layout_width="88dp"
   android:layout_height="100dp"
   android:text="0"
   android:textsize="20dp"
   android:padding="5dp"
   android:background="@drawable/sssssssssssssss"/>
  <button
   android:id="@+id/btn0016"
   android:layout_width="265dp"
   android:layout_height="100dp"
   android:text="="
   android:textsize="20dp"
   android:padding="5dp"
   android:background="#6495ed"/>

 

 </linearlayout>
</linearlayout>

package com.example.myzhuoye;

import android.os.bundle;
import android.view.view;
import android.widget.button;
import android.widget.edittext;

import androidx.annotation.nullable;
import androidx.appcompat.app.appcompatactivity;

public class jisuanji extends appcompatactivity implements view.onclicklistener {
 //结果
 private edittext et001,et002;
 //数字0-9
 private button btn0018, btn0013,btn0014,btn0015,btn009,btn0010,btn0011,btn005,btn006,btn007;
 //运算符,+,-,×，÷,.,=;清除,返回
 private button btn0012,btn008,btn003,btn002,btn0019,btn0016,btn001,btn004;
 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(@nullable bundle savedinstancestate) {
  super.oncreate(savedinstancestate);
  setcontentview(r.layout.layout4);
  //结果
  et001=(edittext)findviewbyid(r.id.et001);
  et002=(edittext)findviewbyid(r.id.et002);
  //数字0-9
  btn0013=(button)findviewbyid(r.id.btn0013);
  btn0014=(button)findviewbyid(r.id.btn0014);
  btn0015=(button)findviewbyid(r.id.btn0015);
  btn009=(button)findviewbyid(r.id.btn009);
  btn0010=(button)findviewbyid(r.id.btn0010);
  btn0011=(button)findviewbyid(r.id.btn0011);
  btn005=(button)findviewbyid(r.id.btn005);
  btn006=(button)findviewbyid(r.id.btn006);
  btn007=(button)findviewbyid(r.id.btn007);
  btn0018=(button)findviewbyid(r.id.btn0018);
  //运算符
  btn004=(button)findviewbyid(r.id.btn004);
  btn0012=(button)findviewbyid(r.id.btn0012);
  btn008=(button)findviewbyid(r.id.btn008);
  btn003=(button)findviewbyid(r.id.btn003);
  btn002=(button)findviewbyid(r.id.btn002);
  btn0019=(button)findviewbyid(r.id.btn0019);
  btn0016=(button)findviewbyid(r.id.btn0016);
  btn001=(button)findviewbyid(r.id.btn001);
  //添加点击事件
  btn0013.setonclicklistener((view.onclicklistener) this);
  btn0014.setonclicklistener((view.onclicklistener) this);
  btn0015.setonclicklistener((view.onclicklistener) this);
  btn009.setonclicklistener((view.onclicklistener) this);
  btn0010.setonclicklistener((view.onclicklistener) this);

  btn0011.setonclicklistener((view.onclicklistener) this);
  btn005.setonclicklistener((view.onclicklistener) this);
  btn006.setonclicklistener((view.onclicklistener) this);
  btn007.setonclicklistener((view.onclicklistener) this);
  btn0018.setonclicklistener((view.onclicklistener) this);

  btn0012.setonclicklistener((view.onclicklistener) this);
  btn008.setonclicklistener((view.onclicklistener) this);
  btn003.setonclicklistener((view.onclicklistener) this);
  btn002.setonclicklistener((view.onclicklistener) this);
  btn0019.setonclicklistener((view.onclicklistener) this);

  btn0016.setonclicklistener((view.onclicklistener) this);
  btn001.setonclicklistener((view.onclicklistener) this);
  btn004.setonclicklistener((view.onclicklistener) this);
 }

 @override
 public void onclick(view v) {
  string string=et001.gettext().tostring();
  switch (v.getid()){
   case r.id.btn0018://0
    num(0);
    break;
   case r.id.btn0013://1
    num(1);
    break;
   case r.id.btn0014://2
    num(2);
    break;
   case r.id.btn0015://3
    num(3);
    break;
   case r.id.btn009://4
    num(4);
    break;
   case r.id.btn0010://5
    num(5);
    break;
   case r.id.btn0011://6
    num(6);
    break;
   case r.id.btn005://7
    num(7);
    break;
   case r.id.btn006://8
    num(8);
    break;
   case r.id.btn007://9
    num(9);
    break;
   case r.id.btn0019://.
    dot();
    break;
   case r.id.btn0012://+
    add();
    break;
   case r.id.btn008://-
    sub();
    break;
   case r.id.btn003://"*"
    multiply();
    break;
   case r.id.btn002://除
    divide();
    break;
   case r.id.btn001://清除
    clear();
    break;
   case r.id.btn004://返回
    back();
    break;
   //计算结果
   case r.id.btn0016://结果
    result();
    break;
   default:
    break;
  }
  et001.settext(text);
  et002.settext(string.valueof(result));
 }
 private void num(int i) {
  text = text + string.valueof(i);
 }

 private void dot() {

  int a=text.length();
  string s01="+";
  string s02="-";
  string s03="×";
  string s04="÷";
  string s05=".";
  if (a!=0) {
   string s=text.substring(a-1,a);
   string s0=text.substring(0,a-1);
   if (s01.equals(s) || s02.equals(s) || s03.equals(s) || s04.equals(s) || s05.equals(s)) {
    text = s0+".";
   }else {
    text += ".";
   }
  } else {
   text = "";
   result =0.0;
   et001.settext("");
   et002.settext("");
  }
 }

 private void clear() {

  text = "";
  result =0.0;
  et001.settext("");
  et002.settext("");

 }

 private void back() {
  if (text.length()!=0){
   string str = text.substring(0, text.length()-1);
   text = str;
  }

  ;

 }

 private void add() {
  int a=text.length();

  string s01="+";
  string s02="-";
  string s03="×";
  string s04="÷";
  string s05=".";
  if (a!=0) {
   string s=text.substring(a-1,a);
   string s0=text.substring(0,a-1);
   if (s01.equals(s) || s02.equals(s) || s03.equals(s) || s04.equals(s) || s05.equals(s)) {
    text = s0+"+";
   }else {
    text += "+";
   }
  } else {
   text = "";
   result =0.0;
   et001.settext("");
   et002.settext("");
  }

 }

 private void sub() {
  int a=text.length();
  string s01="+";
  string s02="-";
  string s03="×";
  string s04="÷";
  string s05=".";
  if (a!=0) {
   string s=text.substring(a-1,a);
   string s0=text.substring(0,a-1);
   if (s01.equals(s) || s02.equals(s) || s03.equals(s) || s04.equals(s) || s05.equals(s)) {
    text = s0+"-";
   }else {
    text += "-";
   }
  } else {
   text = "";
   result =0.0;
   et001.settext("");
   et002.settext("");
  }

 }

 private void multiply() {

  int a=text.length();
  string s01="+";
  string s02="-";
  string s03="×";
  string s04="÷";
  string s05=".";
  if (a!=0) {
   string s=text.substring(a-1,a);
   string s0=text.substring(0,a-1);
   if (s01.equals(s) || s02.equals(s) || s03.equals(s) || s04.equals(s) || s05.equals(s)) {
    text = s0+"×";
   }else {
    text += "×";
   }
  } else {
   text = "";
   result =0.0;
   et001.settext("");
   et002.settext("");
  }

 }

 private void divide() {

  int a=text.length();
  string s01="+";
  string s02="-";
  string s03="×";
  string s04="÷";
  string s05=".";
  if (a!=0) {
   string s=text.substring(a-1,a);
   string s0=text.substring(0,a-1);
   if (s01.equals(s) || s02.equals(s) || s03.equals(s) || s04.equals(s) || s05.equals(s)) {
    text = s0+"÷";
   }else {
    text += "÷";
   }
  } else {
   text = "";
   result =0.0;
   et001.settext("");
   et002.settext("");
  }
 }

 //计算输出结果
 private void result() {
  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;
 }

}

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
 <gradient android:startcolor="#c0000000" android:endcolor="#c0000000" android:angle="90" /><!--背景颜色渐变 angle为渐变角度-->
 <solid android:color=" #8deeee" /><!-- 背景填充颜色 -->
 <stroke android:width="0.5dp" android:color="#ff000000" /><!-- 描边，边框宽度、颜色 -->
 <corners android:radius="0dp" /><!-- 边角圆弧的半径 -->
 <padding android:left="0dp" android:top="0dp" android:right="0dp" android:bottom="0dp" /><!-- 四周留出来的空白 -->
</shape>

<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android">
<gradient android:startcolor="#c0000000" android:endcolor="#c0000000" android:angle="90" /><!--背景颜色渐变 angle为渐变角度-->
<solid android:color="#00ffff" /><!-- 背景填充颜色 -->
<stroke android:width="0.5dp" android:color="#ff000000" /><!-- 描边，边框宽度、颜色 -->
<corners android:radius="0dp" /><!-- 边角圆弧的半径 -->
<padding android:left="0dp" android:top="0dp" android:right="0dp" android:bottom="0dp" /><!-- 四周留出来的空白 -->
</shape>