AndroidStudio实现简单计算器
运行后画面布局：
Java代码：
package com.example.admin.caculator;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
/**
* @author yiyi
* 可能有些许Bug，烦请指正。
*
*
*/
public class MainActivity extends AppCompatActivity {
private int[] idNum = {R.id.txt0, R.id.txt1, R.id.txt2, R.id.txt3,
R.id.txt4, R.id.txt5, R.id.txt6, R.id.txt7, R.id.txt8, R.id.txt9}; //数字Number输入
private int[] idCal = {R.id.txtPlus, R.id.txtMinus, R.id.txtMul, R.id.txtDiv,R.id.txtLeft,R.id.txtRight,R.id.txtDot}; //运算符
private Button[] buttonsCal = new Button[idCal.length];
private Button[] buttonsNum = new Button[idNum.length];
private Button buttonEqu; //=
private Button buttonClear; // AC
private Button buttonDel;
private EditText input ;
private TextView output;
private static String Text;
@Override
/**
* EditText为输入字符行，
* TextView为结果。
*/
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
input = (EditText)findViewById(R.id.input);
input.setText("");
input.setEnabled(false);
output = (TextView) findViewById(R.id.output);
output.setText("");
buttonEqu = (Button)findViewById(R.id.txtIs);
buttonEqu.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
output.setText(new Calculate(input.getText().toString()).str);
}
});
buttonClear = (Button) findViewById(R.id.txtClear);
buttonClear.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
input.setText("");
output.setText("");
}
});
buttonDel = (Button) findViewById(R.id.txtDel);
buttonDel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (!input.getText().toString().isEmpty() ) {
Text = input.getText().toString();
Text = Text.substring(0, Text.length() - 1);
input.setText(Text);
}
}
});
/**
* 注册单击事件
*/
for (int idcal = 0; idcal < idCal.length; idcal++) {
buttonsCal[idcal] = (Button) findViewById(idCal[idcal]);
buttonsCal[idcal].setOnClickListener(new CalOnClick(buttonsCal[idcal].getText().toString()));
}
for (int i = 0; i < idNum.length; i++) {
buttonsNum[i] = (Button) findViewById(idNum[i]);
buttonsNum[i].setOnClickListener(new NumberOnClick(buttonsNum[i].getText().toString()));
}
}
//继承OnClick接口
class NumberOnClick implements View.OnClickListener {
String Msg;
/**
*
* @param msg 点击按钮传入字符
*/
public NumberOnClick(String msg) {
Msg = msg;
}
@Override
public void onClick(View v) {
if (!output.getText().toString().equals("")) {
input.setText("");
output.setText("");
}
input.append(Msg);
}
}
class CalOnClick implements View.OnClickListener{
String Msg;
String[] calSymbol = {"+", "-", "*", "/","."};
public CalOnClick(String msg) {
Msg = msg;
}
@Override
public void onClick(View v) {
if (!output.getText().toString().equals("")) {
input.setText("");
output.setText("");
}
// 检查是否运算符重复输入
for (int i = 0; i < calSymbol.length; i++) {
if (Msg.equals(calSymbol[i])) {
if (input.getText().toString().split("")
[input.getText().toString().split("").length - 1].equals(calSymbol[i])) {
Msg = "";
}
}
}
input.append(Msg);
}
}
/**
* 运算类，返回一个String结果
*/
public class Calculate {
public String s1;
StringBuilder str;
public Calculate(String m) {
this.s1 = m;
try {
eval();
} catch (Exception e) {
str.delete(0, str.length());
str.append("ERROR");
}
}
/**
*中缀表达式转后缀表达式
*
*遍历中缀的list
*1、数字时，加入后缀list
*2、“(”时，压栈
*3、 若为 ')'，则依次弹栈,把弹出的运算符加入后缀表达式中，直到出现'('；
*4、若为运算符，对做如下处置
* 1、如果栈为空，则压栈
* 2、如果栈不为空:
* 1、stack.peek().equals("(") 则压栈
* 2、比较str和stack.peek()的优先级
* 1、如果>,则运算符压栈
* 2、<=的情况：当栈不为空时:
* 1、stack.peek()是左括号，压栈
* 2、<=,把peek加入后缀表达式，弹栈
* 3、>，把运算符压栈，停止对栈的操作
* 执行完栈的操作之后，还得判断:如果栈为空,运算符压栈
*/
public List midToAfter(List midList)throws EmptyStackException{
List afterList=new ArrayList();
Stack stack=new Stack();
for(String str:midList){
int flag=this.matchWitch(str);
switch (flag) {
case 7:
afterList.add(str);
break;
case 1:
stack.push(str);
break;
case 2:
String pop=stack.pop();
while(!pop.equals("(")){
afterList.add(pop);
pop=stack.pop();
}
break;
default:
if(stack.isEmpty()){
stack.push(str);
break;
}
else{
if(stack.peek().equals("(")){
stack.push(str);
break;
}else{
int ji1=this.youxianji(str);
int ji2=this.youxianji(stack.peek());
if(ji1>ji2){
stack.push(str);
}else{
while(!stack.isEmpty()){
String f=stack.peek();
if(f.equals("(")){
stack.push(str);
break;
}else{
if(this.youxianji(str)<=this.youxianji(f)){
afterList.add(f);
stack.pop();
}else{
stack.push(str);
break;
}
}
}
if(stack.isEmpty()){
stack.push(str);
}
}
break;
}
}
}
}
while(!stack.isEmpty()){
afterList.add(stack.pop());
}
StringBuffer sb=new StringBuffer();
for(String s:afterList){
sb.append(s+" ");
}
//System.out.println(sb.toString());
return afterList;
}
/**
判断运算符的优先级
*/
public int youxianji(String str){
int result=0;
if(str.equals("+")||str.equals("-")){
result=1;
}else{
result =2;
}
return result;
}
/**
*判断字符串属于操作数、操作符还是括号
*/
public int matchWitch(String s){
if(s.equals("(")){
return 1;
}else if(s.equals(")")){
return 2;
}else if(s.equals("+")){
return 3;
}else if(s.equals("-")){
return 4;
}else if(s.equals("*")){
return 5;
}else if(s.equals("/")){
return 6;
}else{
return 7;
}
}
/**
*计算a@b的简单方法
*/
public Double singleEval(Double pop2,Double pop1,String str){
Double value=0.0;
if(str.equals("+")){
value=pop2+pop1;
}else if(str.equals("-")){
value=pop2-pop1;
}else if(str.equals("*")){
value=pop2*pop1;
}else {
value=pop2/pop1;
}
return value;
}
private double result;
public double getResult() {
return result;
}
public void setResult(double result) {
this.result = result;
}
private int state;
public int getState() {
return state;
}
public void setState(int state) {
this.state = state;
}
public void countHouzhui(List list){
str = new StringBuilder("");
state=0;
result=0;
Stack stack=new Stack();
for(String str:list){
int flag=this.matchWitch(str);
switch (flag) {
case 3:
case 4:
case 5:
case 6:
Double pop1=stack.pop();
Double pop2=stack.pop();
Double value=this.singleEval(pop2, pop1, str);
stack.push(value);
break;
default:
Double push=Double.parseDouble(str);
stack.push(push);
break;
}
}
if(stack.isEmpty()){
state=1;
}else{
result=stack.peek();
str.append(stack.pop());
}
}
public void eval()throws Exception{
List list=new ArrayList();
//匹配运算符、括号、整数、小数，注意-和*要加\\
Pattern p = Pattern.compile("[+\\-/\\*()]|\\d+\\.?\\d*");
Matcher m = p.matcher(s1);
while(m.find()){
list.add(m.group());
}
List afterList=this.midToAfter(list);
this.countHouzhui(afterList);
}
}
}
XML文件：
（代码来源于：https://blog.csdn.net/orochi1972/article/details/78467510）
按照书上的开发过程和网上网友提供的代码，尝试运行简易计算器app，中间出现的问题通过百度后都能解答，在尝试的过程中对软件的熟悉度有那么一点点的提升，以后要坚持多练习才能更熟练。