Android Simple Calculator

Algorithm used: expression evaluation (infix expression to suffix expression, suffix expression evaluation value)

Not how to design the interface, there is time to beautify!

Mainactivity.java

Package Com.example.calculator;import Java.util.hashmap;import Java.util.linkedlist;import java.util.List;import Java.util.map;import Android.app.activity;import Android.os.bundle;import Android.view.menu;import Android.view.view;import Android.widget.button;import Android.widget.textview;import Android.widget.Toast;public Class Mainactivity extends Activity {String mid=null; TextView textview=null;//operation Fu Yi static linkedlist<string> opstack=new linkedlist<string> ();//Priority mapping static Map<string, integer> priority=new hashmap<string, integer> () {Put ("(", 0);p ut (")", 0);p ut ("+", 1);p ut ("-" , 1);p ut ("x", 2);p ut ("÷", 2);}}; public void init () {textview= (TextView) Findviewbyid (R.id.textview); textview.settextsize (30);} @Overrideprotected void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate); Setcontentview ( R.layout.activity_main); init ();} @Overridepublic boolean Oncreateoptionsmenu (Menu menu) {getmenuinflater (). Inflate (R.menu.main, menu); return true;} Public VoiD Delete (view view) {String text = (string) textview.gettext (); if (Text!=null&&text.length ()!=0) {text= Text.substring (0, Text.length ()-1); Textview.settext (text);}} public void Clear (view view) {Textview.settext ("");} public void Showtext (view view) {button bt= (button) view; string s = (string) bt.gettext ();//toast.maketext (this, S, Toast.length_long). Show (); String text = (string) textview.gettext (); Textview.settext (text+s);} public void Calc (view view) {mid = (String) textview.gettext (); String[] Midsplit=gotosplit (mid);D ouble ans=0.; Try {list<string> after = Midtoafter (Midsplit), ans = aftervalue (after); Textview.settext (ans.tostring ());} catch (Exception e) {Toast.maketext (this, "input not valid, please check", Toast.length_long). Show ();}} Public string[] Gotosplit (String s) {int pre=-1;//The position of the previous symbol, when two symbols together:) * should be divided into: *# otherwise divided into: #* #StringBuffer sb=new StringBuffer ( ); for (int i=0;i<s.length (); i++) {if (S.charat (i)! = '. ') && (S.charat (i) < ' 0 ' | | S.charat (i) > ' 9 ') {if (I-1==pre) {//previous is also the action symbol Sb.append (S.charat(i) + "#");} else Sb.append ("#" +s.charat (i) + "#");p re=i;//update pre}else{sb.append (S.charat (i));}} string[] split = Sb.tostring (). Split ("#"); return split;} /** * infix suffix: * Left-to-right scan expression * A: If the digital direct output * B: if (directly into the stack * C: IF) the stack of operators back to the stack output, until the encounter (so far, the stack is discarded * d other: The priority of the current operator is less than equal to the top of the stack operator priority, then the stack top operation Output. Until it is not less than or empty; */public the current operator into the stack static list<string> midtoafter (String [] mid) throws Exception{linkedlist<string > After=new linkedlist<string> (); int index=0;for (String ss:mid) {if (ss.equals ("=")) continue;if ( Priority.get (ss) ==null) {//description is operand after.add (ss);} else if (ss.equals (")") {Opstack.push (ss);} else if (ss.equals (")")) {while (!opstack.peek (). Equals ("(")) {///not "(", then output, After.add (Opstack.pop ());} Opstack.pop ();//Remove (}else {while (!opstack.isempty () &&priority.get (ss) <=priority.get (Opstack.peek ())) { After.add (Opstack.pop ());} Opstack.push (ss);}} while (!opstack.isempty ()) After.add (Opstack.pop ()), return after;} /** * Suffix evaluation: Left-to-right scan suffix expression * A: if it is a number, directly into the stack * B: If it is an operator, stack two numbers from the stack, calculate by operator, then put the results into the stack, note the two operand order * results: The last stack has only one number,The stack is the answer * @param after * @return */public static double Aftervalue (list<string> after) throws Exception{linkedlist&lt ;D ouble> number=new linkedlist<double> (); for (String Ss:after) {if (Priority.get (ss)!=null) {//is an operator, remove two numbers. Calculates the post-enter number stack by operator Double Y=number.pop ();D ouble x=number.pop (), if (Ss.equals ("+")) Number.push (x+y), Else if (ss.equals ("-")) Number.push (x-y), else if (Ss.equals ("x")) Number.push (x*y), Else if (ss.equals ("÷")) Number.push (x/y);} Else{number.push (double.valueof (ss));}} return Number.pop ();}}

Activity_main.xml

<linearlayout xmlns:android= "http://schemas.android.com/apk/res/android" xmlns:tools= "http// Schemas.android.com/tools "android:layout_width=" match_parent "android:layout_height=" Match_parent "Android:paddi ngbottom= "@dimen/activity_vertical_margin" android:paddingleft= "@dimen/activity_horizontal_margin" Android: paddingright= "@dimen/activity_horizontal_margin" android:paddingtop= "@dimen/activity_vertical_margin" tools: Context= ". Mainactivity "android:orientation=" vertical "> <textview android:id=" @+id/textview "android:l Ayout_width= "Match_parent" android:layout_height= "100DP" android:hint= "0"/> <tablel Ayout android:layout_width= "match_parent" android:layout_height= "match_parent" > <tabler            ow android:layout_width= "match_parent" android:layout_height= "Match_parent" > <button android:layout_width= "60DP"                android:layout_height= "60DP" android:text= "(" android:onclick= "Showtext" /> <button android:layout_width= "60DP" Android                                : layout_height= "60DP" android:text= ")" android:onclick= "Showtext"                /> <button android:layout_width= "60DP" android:layout_height= "60DP" android:text= "C" android:onclick= "clear"/> < Button android:layout_width= "60DP" android:layout_height= "60DP" Android:text = "DEL" android:onclick= "delete"/> </TableRow> <t            Ablerow android:layout_width= "match_parent" android:layout_height= "Match_parent" >         <button        Android:layout_width= "60DP" android:layout_height= "60DP" android:text= "7" android:onclick= "Showtext"/> <button android:layout_ Width= "60DP" android:layout_height= "60DP" android:text= "8" android:onclick= "s                Howtext "/> <button android:layout_width=" 60DP "                                android:layout_height= "60DP" android:text= "9" android:onclick= "Showtext" /> <button android:layout_width= "60DP" Android:layout_hei         ght= "60DP" android:text= "÷" android:onclick= "Showtext"/> </TableRow> <tablerow android:layout_width= "Match_parent" android:layout_height         = "Match_parent"   > <button android:layout_width= "60dp" android:layout_height= "60DP" android:text= "4" android:onclick= "Showtext"/> < Button android:layout_width= "60DP" android:layout_height= "60DP" Android:text                 = "5" android:onclick= "Showtext"/> <button Android:layout_width= "60DP" android:layout_height= "60DP" android:text= "6" and roid:onclick= "Showtext"/> <button android:layout_width= "6                                 0DP "android:layout_height=" 60DP "android:text=" x "android:onclick=" Showtext " /> </TableRow> <tablerow android:layout_width= "MATC H_parent "Android: layout_height= "Match_parent" > <button android:layout_width= "60DP"                                android:layout_height= "60DP" android:text= "1" android:onclick= "Showtext" /> <button android:layout_width= "60DP" Android:layout_hei            ght= "60DP" android:text= "2" android:onclick= "Showtext"/>                <button android:layout_width= "60DP" android:layout_height= "60DP"                 android:text= "3" android:onclick= "Showtext"/> <button                Android:layout_width= "60DP" android:layout_height= "60DP" android:text= "-"             android:onclick= "Showtext"/> </TableRow> <tablerow Android:layoUt_width= "Match_parent" android:layout_height= "match_parent" > <button                Android:layout_width= "60DP" android:layout_height= "60DP" android:text= "." android:onclick= "Showtext"/> <button android:layout_width = "60DP" android:layout_height= "60DP" android:text= "0" android:onclick= "Showte                XT "/> <button android:layout_width=" 60DP "                                android:layout_height= "60DP" android:text= "=" android:onclick= "Calc" /> <button android:layout_width= "60DP" android:layout_height= "60DP "android:text=" + "android:onclick=" Showtext "/> & Lt;/tablerow> </taBlelayout></linearlayout> 

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Android Simple Calculator