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实现简单的Android计算器_安卓计算器代码

作者：我家自动化 | 2024-03-12 08:38:52

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安卓计算器代码

目录

设置UI

实现计算器的代码

按钮点击的实现

 处理输入的表达式

中缀转后缀的函数

计算函数

效果图

设置UI

        首先，让我们先来设置UI。

        在res资源找到values文件夹，右键设置style.xlm文件，即为按钮的样式

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <resources>
  3.     <style name="ButtonStyle" >
  4.         <item name="android:radius">10dp</item>
  5.         <item name="android:textStyle">bold</item>
  6.         <item name="android:textSize">20sp</item>
  7.         <item name="android:color">#000</item>
  8.         <item name="android:borderlessButtonStyle">@style/TextAppearance.AppCompat.Body1</item>
  9.     </style>
  10. </resources>

        其次，让我们在res下的drawable文件夹下新建一个select文件 ，里面是关于按钮的一些的形状、背景颜色、以及点击时变色的设置

        注意：颜色可以按照自己选择的背景图来设置，而不是照搬

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <selector xmlns:android="http://schemas.android.com/apk/res/android">
  3.     <item android:state_pressed="false">
  4.         <shape android:shape="rectangle">
  5.             <solid android:color="#98FF98"/>
  6.             <stroke android:width="5dp"/>
  7.         </shape>
  8.     </item>
  9.  
  10.     <item android:state_pressed="true">
  11.         <shape android:shape="rectangle">
  12.             <solid android:color="#64E986"/>
  13.             <stroke android:width="5dp"/>
  14.         </shape>
  15.     </item>
  16. </selector>

        让我们重新回到activity_main.xlm,这里，我使用的是表格布局嵌套线性布局

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:app="http://schemas.android.com/apk/res-auto"
  4.     xmlns:tools="http://schemas.android.com/tools"
  5.     android:layout_width="match_parent"
  6.     android:layout_height="match_parent"
  7.     android:layout_gravity="center"
  8.     android:gravity="center"
  9.     android:background="@drawable/background"
  10.     android:alpha="1"
  11.     tools:context=".MainActivity">
  12.  
  13.     <EditText
  14.         android:id="@+id/edit"
  15.         android:layout_width="match_parent"
  16.         android:layout_height="225dp"
  17.         android:textSize="40dp"
  18.         android:gravity="right"
  19.         android:cursorVisible="false"
  20.         android:hint="0"
  21.         android:ellipsize="end"/>
  22.  
  23.     <!--    <TextView-->
  24.     <!--        android:id="@+id/text_view"-->
  25.     <!--        android:layout_width="match_parent"-->
  26.     <!--        android:layout_height="wrap_content"-->
  27.     <!--        android:text="0"/>-->
  28.  
  29.     <TableRow>
  30.         <Button
  31.             android:id="@+id/button_delete"
  32.             android:layout_width="90dp"
  33.             android:layout_height="90dp"
  34.             android:layout_marginLeft="10dp"
  35.             style="@style/ButtonStyle"
  36.             android:background="@drawable/select"
  37.             android:alpha="0.4"
  38.             android:gravity="center"
  39.             android:layout_marginTop="10dp"
  40.             android:text="del" />
  41.         <Button
  42.             android:id="@+id/button_brackets_left"
  43.             android:layout_width="90dp"
  44.             android:layout_height="90dp"
  45.             android:layout_marginLeft="10dp"
  46.             android:layout_marginTop="10dp"
  47.             style="@style/ButtonStyle"
  48.             android:background="@drawable/select"
  49.             android:alpha="0.4"
  50.             android:gravity="center"
  51.             android:text="(" />
  52.         <Button
  53.             android:id="@+id/button_brackets_right"
  54.             android:layout_width="90dp"
  55.             android:layout_height="90dp"
  56.             android:layout_marginLeft="10dp"
  57.             android:layout_marginTop="10dp"
  58.             style="@style/ButtonStyle"
  59.             android:background="@drawable/select"
  60.             android:alpha="0.4"
  61.             android:gravity="center"
  62.             android:text=")" />
  63.         <Button
  64.             android:id="@+id/button_divide"
  65.             android:layout_width="90dp"
  66.             android:layout_height="90dp"
  67.             android:layout_marginLeft="10dp"
  68.             style="@style/ButtonStyle"
  69.             android:background="@drawable/select"
  70.             android:alpha="0.4"
  71.             android:gravity="center"
  72.             android:layout_marginTop="10dp"
  73.             android:text="/" />
  74.     </TableRow>
  75.  
  76.     <TableRow>
  77.         <Button
  78.             android:id="@+id/button_7"
  79.             android:layout_width="90dp"
  80.             android:layout_height="90dp"
  81.             android:layout_marginLeft="10dp"
  82.             style="@style/ButtonStyle"
  83.             android:background="@drawable/select"
  84.             android:alpha="0.4"
  85.             android:gravity="center"
  86.             android:layout_marginTop="10dp"
  87.             android:text="7" />
  88.         <Button
  89.             android:id="@+id/button_8"
  90.             android:layout_width="90dp"
  91.             android:layout_height="90dp"
  92.             android:layout_marginLeft="10dp"
  93.             style="@style/ButtonStyle"
  94.             android:background="@drawable/select"
  95.             android:alpha="0.4"
  96.             android:gravity="center"
  97.             android:layout_marginTop="10dp"
  98.             android:text="8" />
  99.         <Button
  100.             android:id="@+id/button_9"
  101.             android:layout_width="90dp"
  102.             android:layout_height="90dp"
  103.             android:layout_marginLeft="10dp"
  104.             style="@style/ButtonStyle"
  105.             android:background="@drawable/select"
  106.             android:alpha="0.4"
  107.             android:gravity="center"
  108.             android:layout_marginTop="10dp"
  109.             android:text="9" />
  110.         <Button
  111.             android:id="@+id/button_multiply"
  112.             android:layout_width="90dp"
  113.             android:layout_height="90dp"
  114.             android:layout_marginLeft="10dp"
  115.             style="@style/ButtonStyle"
  116.             android:background="@drawable/select"
  117.             android:alpha="0.4"
  118.             android:gravity="center"
  119.             android:layout_marginTop="10dp"
  120.             android:text="*" />
  121.  
  122.     </TableRow>
  123.  
  124.     <TableRow>
  125.         <Button
  126.             android:id="@+id/button_4"
  127.             android:layout_width="90dp"
  128.             android:layout_height="90dp"
  129.             android:layout_marginLeft="10dp"
  130.             style="@style/ButtonStyle"
  131.             android:background="@drawable/select"
  132.             android:alpha="0.4"
  133.             android:gravity="center"
  134.             android:layout_marginTop="10dp"
  135.             android:text="4" />
  136.         <Button
  137.             android:id="@+id/button_5"
  138.             android:layout_width="90dp"
  139.             android:layout_height="90dp"
  140.             android:layout_marginLeft="10dp"
  141.             style="@style/ButtonStyle"
  142.             android:background="@drawable/select"
  143.             android:alpha="0.4"
  144.             android:gravity="center"
  145.             android:layout_marginTop="10dp"
  146.             android:text="5" />
  147.         <Button
  148.             android:id="@+id/button_6"
  149.             android:layout_width="90dp"
  150.             android:layout_height="90dp"
  151.             android:layout_marginLeft="10dp"
  152.             style="@style/ButtonStyle"
  153.             android:background="@drawable/select"
  154.             android:alpha="0.4"
  155.             android:gravity="center"
  156.             android:layout_marginTop="10dp"
  157.             android:text="6" />
  158.         <Button
  159.             android:id="@+id/button_add"
  160.             android:layout_width="90dp"
  161.             android:layout_height="90dp"
  162.             android:layout_marginLeft="10dp"
  163.             style="@style/ButtonStyle"
  164.             android:background="@drawable/select"
  165.             android:alpha="0.4"
  166.             android:gravity="center"
  167.             android:layout_marginTop="10dp"
  168.             android:text="+" />
  169.  
  170.     </TableRow>
  171.  
  172.     <TableRow>
  173.         <Button
  174.             android:id="@+id/button_1"
  175.             android:layout_width="90dp"
  176.             android:layout_height="90dp"
  177.             android:layout_marginLeft="10dp"
  178.             style="@style/ButtonStyle"
  179.             android:background="@drawable/select"
  180.             android:alpha="0.4"
  181.             android:gravity="center"
  182.             android:layout_marginTop="10dp"
  183.             android:text="1" />
  184.  
  185.         <Button
  186.             android:id="@+id/button_2"
  187.             android:layout_width="90dp"
  188.             android:layout_height="90dp"
  189.             android:layout_marginLeft="10dp"
  190.             style="@style/ButtonStyle"
  191.             android:background="@drawable/select"
  192.             android:alpha="0.4"
  193.             android:gravity="center"
  194.             android:layout_marginTop="10dp"
  195.             android:text="2" />
  196.  
  197.         <Button
  198.             android:id="@+id/button_3"
  199.             android:layout_width="90dp"
  200.             android:layout_height="90dp"
  201.             android:layout_marginLeft="10dp"
  202.             style="@style/ButtonStyle"
  203.             android:background="@drawable/select"
  204.             android:alpha="0.4"
  205.             android:gravity="center"
  206.             android:layout_marginTop="10dp"
  207.             android:text="3" />
  208.         <Button
  209.             android:id="@+id/button_subtract"
  210.             style="@style/ButtonStyle"
  211.             android:layout_width="90dp"
  212.             android:layout_height="90dp"
  213.             android:layout_marginLeft="10dp"
  214.             android:layout_marginTop="10dp"
  215.             android:alpha="0.4"
  216.             android:background="@drawable/select"
  217.             android:gravity="center"
  218.             android:text="-" />
  219.  
  220.     </TableRow>
  221.  
  222.     <TableRow >
  223.         <Button
  224.             android:id="@+id/button_ac"
  225.             android:layout_width="90dp"
  226.             android:layout_height="90dp"
  227.             android:layout_marginLeft="10dp"
  228.             style="@style/ButtonStyle"
  229.             android:background="@drawable/select"
  230.             android:alpha="0.4"
  231.             android:gravity="center"
  232.             android:layout_marginTop="10dp"
  233.             android:text="AC" />
  234.  
  235.         <Button
  236.             android:id="@+id/button_0"
  237.             style="@style/ButtonStyle"
  238.             android:layout_width="90dp"
  239.             android:layout_height="90dp"
  240.             android:layout_marginLeft="10dp"
  241.             android:layout_marginTop="10dp"
  242.             android:alpha="0.4"
  243.             android:background="@drawable/select"
  244.             android:gravity="center"
  245.             android:text="0" />
  246.         <!--            android:layout_columnSpan="2"-->
  247.         <!--            android:layout_gravity="fill_horizontal"-->
  248.         <Button
  249.             android:id="@+id/button_point"
  250.             style="@style/ButtonStyle"
  251.             android:layout_width="90dp"
  252.             android:layout_height="90dp"
  253.             android:layout_marginLeft="10dp"
  254.             android:layout_marginTop="10dp"
  255.             android:alpha="0.4"
  256.             android:background="@drawable/select"
  257.             android:gravity="center"
  258.             android:text="." />
  259.  
  260.         <Button
  261.             android:id="@+id/button_equal"
  262.             style="@style/ButtonStyle"
  263.             android:layout_width="90dp"
  264.             android:layout_height="90dp"
  265.             android:layout_marginLeft="10dp"
  266.             android:layout_marginTop="10dp"
  267.             android:alpha="0.4"
  268.             android:background="@drawable/select"
  269.             android:gravity="center"
  270.             android:text="=" />
  271.     </TableRow>
  272.  
  273. </TableLayout>

实现计算器的代码

按钮点击的实现

  1. public class MainActivity extends AppCompatActivity implements View.OnClickListener {
  2.  
  3.     public static EditText editText;
  4.     public static String string = "";
  5.     public static int left = 0;
  6.     public static int right = 0;
  7.     public static boolean pointFlat = true;
  8.     public static boolean isResult = false;
  9.  
  10.     public static Button tempButton;
  11.     @Override
  12.     protected void onCreate(Bundle savedInstanceState) {
  13.         super.onCreate(savedInstanceState);
  14.         setContentView(R.layout.activity_main);
  15.  
  16.         Button button1 = (Button) findViewById(R.id.button_1);
  17.         Button button2 = (Button) findViewById(R.id.button_2);
  18.         Button button3 = (Button) findViewById(R.id.button_3);
  19.         Button button4 = (Button) findViewById(R.id.button_4);
  20.         Button button5 = (Button) findViewById(R.id.button_5);
  21.         Button button6 = (Button) findViewById(R.id.button_6);
  22.         Button button7 = (Button) findViewById(R.id.button_7);
  23.         Button button8 = (Button) findViewById(R.id.button_8);
  24.         Button button9 = (Button) findViewById(R.id.button_9);
  25.         Button button0 = (Button) findViewById(R.id.button_0);
  26.         Button add = (Button) findViewById(R.id.button_add);
  27.         Button subtract = (Button) findViewById(R.id.button_subtract);
  28.         Button multiply = (Button) findViewById(R.id.button_multiply);
  29.         Button divide = (Button) findViewById(R.id.button_divide);
  30.         Button ac = (Button) findViewById(R.id.button_ac);
  31.         Button delete = (Button) findViewById(R.id.button_delete);
  32.         Button equal = (Button) findViewById(R.id.button_equal);
  33.         Button button_left = (Button) findViewById(R.id.button_brackets_left);
  34.         Button button_right = (Button) findViewById(R.id.button_brackets_right);
  35.         Button point = (Button) findViewById(R.id.button_point);
  36.  
  37.         editText = (EditText) findViewById(R.id.edit);
  38.  
  39.         button1.setOnClickListener(this);
  40.         button2.setOnClickListener(this);
  41.         button3.setOnClickListener(this);
  42.         button4.setOnClickListener(this);
  43.         button5.setOnClickListener(this);
  44.         button6.setOnClickListener(this);
  45.         button7.setOnClickListener(this);
  46.         button8.setOnClickListener(this);
  47.         button9.setOnClickListener(this);
  48.         button0.setOnClickListener(this);
  49.         add.setOnClickListener(this);
  50.         subtract.setOnClickListener(this);
  51.         multiply.setOnClickListener(this);
  52.         divide.setOnClickListener(this);
  53.         ac.setOnClickListener(this);
  54.         delete.setOnClickListener(this);
  55.         button_left.setOnClickListener(this);
  56.         button_right.setOnClickListener(this);
  57.         equal.setOnClickListener(this);
  58.         point.setOnClickListener(this);
  59.  
  60.     }
  61.  
  62.     @Override
  63.     public void onClick(View view) {
  64.         if (isResult){
  65.             String tempbutton;
  66.             tempButton = (Button) findViewById(view.getId());
  67. //        tempButton.setOnClickListener(this);
  68.             tempbutton = String.valueOf(tempButton.getText());
  69.             if (tempbutton.matches("[\\+\\-\\*\\/]")){
  70.                 isResult = false;
  71.             }else if(tempbutton.equals("=")){
  72.             } else if (tempbutton.equals("del")) {
  73.                 isResult = false;
  74.             } else {
  75.                 string = "";
  76.                 editText.setText(string);
  77.                 isResult = false;
  78.             }
  79.         }
  80.         if (view.getId() == R.id.button_1) {
  81.             string += "1";
  82.             editText.setText(string);
  83.         }
  84.         if (view.getId() == R.id.button_2) {
  85.             string += "2";
  86.             editText.setText(string);
  87.         }
  88.         if (view.getId() == R.id.button_3) {
  89.             string += "3";
  90.             editText.setText(string);
  91.         }
  92.         if (view.getId() == R.id.button_4) {
  93.             string += "4";
  94.             editText.setText(string);
  95.         }
  96.         if (view.getId() == R.id.button_5) {
  97.             string += "5";
  98.             editText.setText(string);
  99.         }
  100.         if (view.getId() == R.id.button_6) {
  101.             string += "6";
  102.             editText.setText(string);
  103.         }
  104.         if (view.getId() == R.id.button_7) {
  105.             string += "7";
  106.             editText.setText(string);
  107.         }
  108.         if (view.getId() == R.id.button_8) {
  109.             string += "8";
  110.             editText.setText(string);
  111.         }
  112.         if (view.getId() == R.id.button_9) {
  113.             string += "9";
  114.             editText.setText(string);
  115.         }
  116.         if (view.getId() == R.id.button_0) {
  117.             int length_0 = string.length();
  118.             if (length_0 > 0 && String.valueOf(string.charAt(length_0 - 1)).equals("/")) {
  119.                 editText.setText(string + "0" + "   tip : 0不能作为除数");
  120.             } else {
  121.                 string += "0";
  122.                 editText.setText(string);
  123.             }
  124.         }
  125.         if (view.getId() == R.id.button_add) {
  126.             int length_add = string.length();
  127.             if (length_add == 0){
  128.                 string = "+";
  129.             }else if (String.valueOf(string.charAt(length_add - 1)).equals(".")) {
  130.                 string += "0+";
  131.             } else if (String.valueOf(string.charAt(length_add - 1)).matches("[\\-\\*\\/\\+]")) {
  132.                 string = string.substring(0,length_add - 1);
  133.                 string += "+";
  134.             } else {
  135.                 string += "+";
  136.             }
  137.             editText.setText(string);
  138.             pointFlat = true;
  139.         }
  140.         if (view.getId() == R.id.button_subtract) {
  141.             int length_sub = string.length();
  142.             if (length_sub == 0) {
  143.                 string += "-";
  144.             } else if (String.valueOf(string.charAt(length_sub - 1)).matches("[\\+\\-\\*\\/]{1}")) {
  145.                 string += "(0-";
  146.                 left++;
  147.             }//减号前有运算符的情况
  148.             else if (String.valueOf(string.charAt(length_sub - 1)).equals(".")) {
  149.                 string += "0-";
  150.             } else {
  151.                 string += "-";
  152.             }
  153.             editText.setText(string);
  154.             pointFlat = true;
  155.         }
  156.         if (view.getId() == R.id.button_multiply) {
  157.             int length_mul = string.length();
  158.             if (length_mul == 0){
  159.                 string = "*";
  160.             } else if (String.valueOf(string.charAt(length_mul - 1)).equals(".")) {
  161.                 string += "0*";
  162.             } else if (String.valueOf(string.charAt(length_mul - 1)).matches("[\\-\\+\\/\\*]")) {
  163.                 string = string.substring(0,length_mul - 1);
  164.                 string += "*";
  165.             }  else {
  166.                 string += "*";
  167.             }
  168.             editText.setText(string);
  169.             pointFlat = true;
  170.         }
  171.         if (view.getId() == R.id.button_divide) {
  172.             int length_divide = string.length();
  173.             if (length_divide == 0){
  174.                 string = "/";
  175.             }else if (String.valueOf(string.charAt(length_divide - 1)).equals(".")) {
  176.                 string += "0/";
  177.             } else if (String.valueOf(string.charAt(length_divide - 1)).matches("[\\+\\*\\-\\/]")) {
  178.                 string = string.substring(0,length_divide - 1);
  179.                 string += "/";
  180.             }  else {
  181.                 string += "/";
  182.             }
  183.             editText.setText(string);
  184.             pointFlat = true;
  185.         }
  186.         if (view.getId() == R.id.button_ac) {
  187.             string = "";
  188.             left = right = 0;
  189.             pointFlat = true;
  190.             editText.setText(string);
  191.         }
  192.         if (view.getId() == R.id.button_delete) {
  193.             int length_del = string.length();
  194.             if (length_del > 0){
  195.                 String temp = String.valueOf(string.charAt(length_del - 1));
  196.                 if (temp.equals(".")) {
  197.                     pointFlat = true;
  198.                 } else if (temp.equals("(")) {
  199.                     left--;
  200.                 } else if (temp.equals(")")) {
  201.                     right--;
  202.                 }
  203.                 string = string.substring(0, length_del - 1);
  204.                 editText.setText(string);
  205.                 if (string.equals("")) {
  206.                     left = right = 0;
  207.                     pointFlat = true;
  208.                     isResult = false;
  209.                 }
  210.             }
  211.         }
  212.         if (view.getId() == R.id.button_brackets_left) {
  213.             string += "(";
  214.             left++;
  215.             editText.setText(string);
  216.         }
  217.         if (view.getId() == R.id.button_brackets_right) {
  218.             int length_right = string.length();
  219.             if (string.charAt(length_right - 1) == '.'){
  220.                 string += "0)";
  221.                 right++;
  222.                 editText.setText(string);
  223.             }else {
  224.                 string += ")";
  225.                 right++;
  226.                 editText.setText(string);
  227.             }
  228.  
  229.         }
  230.         if (view.getId() == R.id.button_point) {
  231.             if (pointFlat) {
  232.                 int length_point = string.length();
  233.                 if (length_point == 0 || (length_point > 0
  234.                         && String.valueOf(string.charAt(length_point - 1)).matches("[\\+\\-\\*\\/\\(]{1}"))) {
  235.                     string += "0.";
  236.                     editText.setText(string);
  237.                     pointFlat = false;
  238.                 } else {
  239.                     string += ".";
  240.                     editText.setText(string);
  241.                     pointFlat = false;
  242.                 }
  243.             }
  244.         }
  245.         if (view.getId() == R.id.button_equal) {
  246.             String temp;
  247.             if(string.equals("")){
  248.             }else {
  249.                 isResult = true;
  250.                 string = temp = Equal(string);
  251.                 if (string.equals("Error")) {
  252.                     editText.setText("Error");
  253.                     left = right = 0;
  254.                     pointFlat = true;
  255.                 }else if (string.matches("^[+-]?[1-9]\\d*$") || string.matches("^[+-]?\\d+(\\.\\d+)$")
  256.                         || string.equals("0")){
  257.                     editText.setText(temp + "\n" + "= " + string);
  258.                     pointFlat = true;
  259.                     left = right = 0;
  260.                 } else {
  261.                     string = Deal(string);//中缀表达式转后缀表达式
  262.                     string = Calculate(string);
  263.                     editText.setText(temp + "\n" + "= " + string);
  264.                     left = right = 0;
  265.                     isResult = true;
  266.                     pointFlat = true;
  267.                 }
  268.             }
  269.         }
  270.     }

 处理输入的表达式

        这个函数是处理一些不完整的输入比如少括号、小数点后没有数值、表达式前后是计算符号等等，以提高该计算器的鲁棒性

  1. public String Equal(String string){
  2.         int length_equ = string.length();
  3.         if(length_equ == 1 && (string.equals("(") || string.equals(")"))){
  4.             string = "Error";
  5.             return string;
  6.         }else if (String.valueOf(string.charAt(0)).equals(")")){
  7.             string = "Error";
  8.             return string;
  9.         }
  10.         if (length_equ == 2 && string.equals("()")){
  11.             string = "Error";
  12.             return string;
  13.         }
  14.         if (length_equ - 1 >= 0 && String.valueOf(string.charAt(length_equ - 1)).matches("[\\*\\/]{1}")){
  15.             string += "1";
  16.         } else if (length_equ - 1 >= 0 && String.valueOf(string.charAt(length_equ - 1)).matches("[\\+\\-\\.]{1}")) {
  17.             string += "0";
  18.         }//结尾是运算符的情况
  19.         if (String.valueOf(string.charAt(0)).matches("[\\+\\-\\*\\/]{1}")){
  20.             string = "0" + string;
  21.         } //开头是运算符的情况
  22.         while(left != right){
  23.             if (left > right){
  24.                 right++;
  25.                 string += ")";
  26.             }else if(left < right){
  27.                 string = "Error";
  28.                 return string;
  29.             }
  30.         }//括号不匹配的情况
  31.  
  32.         for (int i = 0; i < string.length(); i++) {
  33.             String temp = String.valueOf(string.charAt(i));
  34.             if (temp.equals("(") && i + 1 < string.length()
  35.                     && String.valueOf(string.charAt(i + 1)).matches("[\\+\\*\\/\\)]{1}")) {
  36.                 string = "Error";
  37.                 break;
  38.             } else if (temp.equals(")") && i - 1 >= 0 &&
  39.                     String.valueOf(string.charAt(i - 1)).matches("[\\+\\-\\*\\/\\(]{1}")) {
  40.                 string = "Error";
  41.                 break;
  42.             } //出现(+*/  或者  +-*/)的情况
  43.             if (temp.equals("(") && i - 1 > 0
  44.                     && String.valueOf(string.charAt(i - 1)).matches("[0-9\\.\\)]{1}")) {
  45.                 string = "Error";
  46.                 break;
  47.             } else if (temp.equals(")") && i + 1 < string.length()
  48.                     && String.valueOf(string.charAt(i + 1)).matches("[0-9\\(\\.\\(]{1}")) {
  49.                 string = "Error";
  50.                 break;
  51.             }//防止出现[0-9](  和  )[0-9]的情况
  52.         }
  53.         if (string.length() >= 2 && string.charAt(0) == '(' && string.charAt(string.length() - 1) == ')'){
  54.             String temp = string.substring(1,string.length() - 1);
  55.             if (temp.matches("^[+-]?[1-9]\\d*$") || temp.matches("^[+-]?\\d+(\\.\\d+)$")
  56.                     || temp.equals("0")){
  57.                 return temp;
  58.             }
  59.         }
  60.         return string;
  61.     }

中缀转后缀的函数

        中缀转后缀是实现该计算器的核心算法，没学过的建议先去补一下该方面的知识

        中缀表达式转后缀表达式

  1. public String Deal(String infix){
  2.         Stack<String> stack = new Stack<>();
  3.         StringBuilder postfix = new StringBuilder();
  4.         int length = infix.length();
  5.         for (int i = 0; i < length; i++){
  6.             String temp;
  7.             String charAt = String.valueOf(infix.charAt(i));
  8.             if (charAt.equals("(")){
  9.                 stack.push(String.valueOf(charAt));
  10.             } else if (charAt.equals("+") || charAt.equals("-")) {
  11.                 while (!stack.isEmpty()){
  12.                     temp = stack.peek();
  13.                     if (temp.equals("(")){
  14.                         break;
  15.                     }
  16.                     postfix.append(" ").append(stack.pop());
  17.                 }
  18.                 stack.push(charAt);
  19.             } else if (charAt.equals("*") || charAt.equals("/")) {
  20.                 while (!stack.isEmpty()){
  21.                     temp = stack.pop();
  22.                     if (temp.equals("(")  || temp.equals("+")  || temp.equals("-")){
  23.                         stack.push(temp);
  24.                         break;
  25.                     }
  26.                     postfix.append(" ").append(temp);
  27.                 }
  28.                 stack.push(charAt);
  29.             } else if (charAt.equals(")")) {
  30.                 while (!stack.isEmpty()){
  31.                     temp = stack.pop();
  32.                     if (!temp.equals("(")){
  33.                         postfix.append(" ").append(temp);
  34.                     }else {
  35.                         break;
  36.                     }
  37.                 }
  38.             } else if (charAt.matches("[0-9]|\\.")){
  39.                 postfix.append(" ").append(charAt);
  40.                 if (i < length - 1){
  41.                     int j = i + 1;
  42.                     String nextNumber = String.valueOf(infix.charAt(j));
  43.                     while (j < length && nextNumber.matches("[0-9]|\\.")){
  44.                         postfix.append(nextNumber);
  45.                         if (++j < length)
  46.                             nextNumber = String.valueOf(infix.charAt(j));
  47.                     }
  48.                     i = j - 1;
  49.                 }
  50.             }
  51.         }
  52.         while (!stack.isEmpty()){
  53.             postfix.append(" ").append(stack.pop());
  54.         }
  55.         return postfix.toString().trim();
  56.     }

计算函数

        处理完输入的字符串接下来就是计算了，这里全程使用Bigdecimal，在除法处使用了double，因为Bigdecimal精度是十分准确的，在计算无限小数时无法输出会报错，除非设置四舍五入，但是精度的话无法控制得很好，所以我结合两者一起使用

  1. public String Calculate(@NonNull String s){
  2.         String[] nums = s.split(" ");
  3.         Stack<String> stack = new Stack<>();
  4.         BigDecimal big1,big2,big;
  5.         String result = "";
  6.         for(String str : nums){
  7.                 if (str.matches("^[+-]?[1-9]\\d*$") || str.matches("^[+-]?\\d+(\\.\\d+)$") || str.equals("0")){
  8.                     stack.push(str);
  9.                 } else if (str.equals("+")){
  10.                     big1 = new BigDecimal(stack.pop());
  11.                     big2 = new BigDecimal(stack.pop());
  12.                     big = big2.add(big1);
  13.                     result = big + "";
  14.                     stack.push(result);
  15.                 } else if (str.equals("-")) {
  16.                     big1 = new BigDecimal(stack.pop());
  17.                     big2 = new BigDecimal(stack.pop());
  18.                     big = big2.subtract(big1);
  19.                     result = big + "";
  20.                     stack.push(result);
  21.                 } else if (str.equals("*")) {
  22.                     big1 = new BigDecimal(stack.pop());
  23.                     big2 = new BigDecimal(stack.pop());
  24.                     big = big2.multiply(big1);
  25.                     result = big + "";
  26.                     stack.push(result);
  27.                 } else if (str.equals("/")) {
  28.                     String temp1 = stack.pop();
  29.                     String temp2 = stack.pop();
  30.                     big1 = new BigDecimal(temp1);
  31.                     big2 = new BigDecimal(temp2);
  32.                     double b1 = Double.valueOf(temp1);
  33.                     double b2 = Double.valueOf(temp2);
  34.                     if (big1.compareTo(BigDecimal.ZERO) == 0){
  35.                         return "Error : 除数不能为0";
  36.                     }
  37.                     if (temp1.length() <= 20 && temp2.length() <= 20){
  38.                         double b = b2 / b1;
  39.                         result = b + "";
  40.                     }else {
  41.                         big = big2.divide(big1,BigDecimal.ROUND_HALF_UP);
  42.                         result = new BigDecimal(big + "").setScale(12, RoundingMode.HALF_UP) + "";
  43.                     }
  44.                     stack.push(result);
  45.                 } else {
  46.                     return "Error : " + str + "不是数字";
  47.                 }
  48.             }
  49.         return result;
  50.     }

效果图

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