在android studio中做一个简单计算器APP
实验要求
1.界面按书上例2-9设计
2.实现其具体功能：
1）代码注释
2）在博客上写一个开发日志
实现过程
1.新建项目
使用Android Studio新建一个空项目
2.添加布局
在这里，我是用的是课本例2-9的网格布局，在界面设计区域中设置一个6行4列的网格布局，第1行为显示数据的文本标签，第2行为清除数据的按钮，第3~6行均划分为4列，共安排16个按钮，分别代表了数字0、1、2、......、9及加、减、乘、除、等号等符号。代码如下：
<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:columnCount="4"
android:rowCount="6">
<!--文本标签-->
<EditText
android:id="@+id/result"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_columnSpan="4"
android:layout_marginLeft="4px"
android:enabled="false"
android:gravity="left"
android:text="0"
android:textSize="50dip" />
<Button
android:id="@+id/cls"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_columnSpan="4"
android:text="清除"
android:textSize="26sp" />
<Button
android:id="@+id/one"
android:text="1"
android:textSize="26sp" />
<Button
android:id="@+id/two"
android:text="2"
android:textSize="26sp" />
<Button
android:id="@+id/three"
android:text="3"
android:textSize="26sp" />
<Button
android:id="@+id/add"
android:text="+"
android:textSize="26sp" />
<Button
android:id="@+id/four"
android:text="4"
android:textSize="26sp" />
<Button
android:id="@+id/five"
android:text="5"
android:textSize="26sp" />
<Button
android:id="@+id/six"
android:text="6"
android:textSize="26sp" />
<Button
android:id="@+id/sub"
android:text="-"
android:textSize="26sp" />
<Button
android:id="@+id/seven"
android:text="7"
android:textSize="26sp" />
<Button
android:id="@+id/eight"
android:text="8"
android:textSize="26sp" />
<Button
android:id="@+id/nine"
android:text="9"
android:textSize="26sp" />
<Button
android:id="@+id/mul"
android:text="*"
android:textSize="26sp" />
<Button
android:id="@+id/spot"
android:text="."
android:textSize="26sp" />
<Button
android:id="@+id/zero"
android:text="0"
android:textSize="26sp" />
<Button
android:id="@+id/equal"
android:text="="
android:textSize="26sp" />
<Button
android:id="@+id/div"
android:text="/"
android:textSize="26sp" />
</GridLayout>
3.MainActivity的编写
这部分就是对各个按钮点击事件的处理，也就是对键入的数字进行运算，判断之类的。代码如下：
package com.example.calculate;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import java.lang.reflect.Method;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity{
private StringBuilder show_equation=new StringBuilder();//显示运算式
private ArrayList calculate_equation;//计算式
private int signal=0;//为0 时表示刚输入状态；为1 时表示当前在输出结果上继续输入
@Override
protected void onCreate(Bundle savedInstanceState) { //Activity的生命周期法
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//初始化
show_equation=new StringBuilder();
calculate_equation=new ArrayList<>();
Button zero=(Button)findViewById(R.id.zero);
Button one=(Button)findViewById(R.id.one);
Button two=(Button)findViewById(R.id.two);
Button three=(Button)findViewById(R.id.three);
Button four=(Button)findViewById(R.id.four);
Button five=(Button)findViewById(R.id.five);
Button six=(Button)findViewById(R.id.six);
Button seven=(Button)findViewById(R.id.seven);
Button eight=(Button)findViewById(R.id.eight);
Button nine=(Button)findViewById(R.id.nine);
Button cls=(Button)findViewById(R.id.cls);
Button div=(Button)findViewById(R.id.div);
Button mul=(Button)findViewById(R.id.mul);
Button sub=(Button)findViewById(R.id.sub);
Button add=(Button)findViewById(R.id.add);
final Button equal=(Button)findViewById(R.id.equal);
final Button point=(Button)findViewById(R.id.spot);
final EditText result=(EditText)findViewById(R.id.result);
result.setCursorVisible(true);
disableShowInput(result);
//点击文本框时光标始终在文本末尾
result.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
result.setSelection(result.getText().length());
}
});
//数字0~9键按钮监听器
zero.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v){
if(!(show_equation.toString().equals("0"))){
if(signal==0){
show_equation.append("0");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
show_equation.delete(0,show_equation.length());
show_equation.append("0");
result.setText(show_equation);
result.setSelection(result.getText().length());
signal=0;
}
}
}
});
one.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(signal==0){
show_equation.append("1");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
show_equation.delete(0,show_equation.length());
show_equation.append("1");
result.setText(show_equation);
result.setSelection(result.getText().length());
signal=0;
}
}
});
two.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(signal==0){
show_equation.append("2");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
show_equation.delete(0,show_equation.length());
show_equation.append("2");
result.setText(show_equation);
result.setSelection(result.getText().length());
signal=0;
}
}
});
three.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(signal==0){
show_equation.append("3");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
show_equation.delete(0,show_equation.length());
show_equation.append("3");
result.setText(show_equation);
result.setSelection(result.getText().length());
signal=0;
}
}
});
four.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(signal==0){
show_equation.append("4");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
show_equation.delete(0,show_equation.length());
show_equation.append("4");
result.setText(show_equation);
result.setSelection(result.getText().length());
signal=0;
}
}
});
five.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(signal==0){
show_equation.append("5");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
show_equation.delete(0,show_equation.length());
show_equation.append("5");
result.setText(show_equation);
result.setSelection(result.getText().length());
signal=0;
}
}
});
six.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(signal==0){
show_equation.append("6");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
show_equation.delete(0,show_equation.length());
show_equation.append("6");
result.setText(show_equation);
result.setSelection(result.getText().length());
signal=0;
}
}
});
seven.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(signal==0){
show_equation.append("7");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
show_equation.delete(0,show_equation.length());
show_equation.append("7");
result.setText(show_equation);
result.setSelection(result.getText().length());
signal=0;
}
}
});
eight.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(signal==0){
show_equation.append("8");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
show_equation.delete(0,show_equation.length());
show_equation.append("8");
result.setText(show_equation);
result.setSelection(result.getText().length());
signal=0;
}
}
});
nine.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(signal==0){
show_equation.append("9");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
show_equation.delete(0,show_equation.length());
show_equation.append("9");
result.setText(show_equation);
result.setSelection(result.getText().length());
signal=0;
}
}
});
//清零按钮监听器
cls.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
show_equation.delete(0,show_equation.length());
calculate_equation.clear();
signal=0;
result.setText(""); //显示运算式归零并清空文本框
}
});
//小数点按钮监听器
point.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(signal==0){
String a=show_equation.toString();
if(a.equals("")){
show_equation.append(".");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else{
int i;
char t='0';
for(i=a.length();i>0;i--){
t=a.charAt(i-1); //若重复运算符号则中断
if(t=='.'||t=='+'||t=='-'||t=='*'||t=='/')
break;
}
if(i==0){
show_equation.append(".");
result.setText(show_equation);
result.setSelection(result.getText().length());
}else if(t=='+'||t=='-'||t=='*'||t=='/'){
show_equation.append(".");
result.setText(show_equation);
result.setSelection(result.getText().length());
}
}
}else{
show_equation.delete(0,show_equation.length());
show_equation.append(".");
result.setText(".");
result.setSelection(result.getText().length());
signal=0;
}
}
});
//等号按钮监听器
equal.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//判断用户是否输入了内容
if(!show_equation.toString().equals("")){
signal=1;
char temp=show_equation.charAt(show_equation.length()-1);
if(show_equation.charAt(0)=='-')
show_equation.insert(0,"0");
if(temp=='+'||temp=='-')
show_equation.append("0");
if(temp=='*'||temp=='/')
show_equation.append("1");
StringBuilder temp1=new StringBuilder();
for(int i=0;i<show_equation.length();i++){
if(show_equation.charAt(i)>='0'&&show_equation.charAt(i)<='9'||show_equation.charAt(i)=='.'){
temp1.append(String.valueOf(show_equation.charAt(i)));
}else if(show_equation.charAt(i)=='N'){
calculate_equation.add("NaN");
//跳过2个字符
i=i+2;
}else if(show_equation.charAt(i)=='∞'){
calculate_equation.add("∞");
}
else
{
if(temp1.length()!=0){
calculate_equation.add(temp1.toString());
temp1.delete(0,temp1.length());
}
calculate_equation.add(String.valueOf(show_equation.charAt(i)));
}
}
if(temp1.length()!=0){
calculate_equation.add(temp1.toString());
}
calculate_equation.add("#");
String temp8=calculate(calculate_equation);
result.setText(temp8);
result.setSelection(result.getText().length());
show_equation.delete(0,show_equation.length());
calculate_equation.clear();
show_equation.append(temp8);
}
}
});
//加号按钮监听器
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//判断用户是否输入了内容
if(!(show_equation.toString().equals(""))) {
signal=0;
char temp=show_equation.charAt(show_equation.length()-1);
if(temp=='+'||temp=='-'||temp=='*'||temp=='/')
{
show_equation.deleteCharAt(show_equation.length()-1);
show_equation.append("+");
}
else
show_equation.append("+");
result.setText(show_equation);
result.setSelection(result.getText().length());
}
}
});
//减号按钮监听器
sub.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//判断用户是否输入了内容
if(!(show_equation.toString().equals(""))) {
signal=0;
char temp=show_equation.charAt(show_equation.length()-1);
if(temp=='+'||temp=='-'||temp=='*'||temp=='/')
{
show_equation.deleteCharAt(show_equation.length()-1);
show_equation.append("-");
}
else
show_equation.append("-");
result.setText(show_equation);
result.setSelection(result.getText().length());
}
}
});
//乘号按钮监听器
mul.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//判断用户是否输入了内容
if(!(show_equation.toString().equals(""))) {
signal=0;
char temp=show_equation.charAt(show_equation.length()-1);
if(temp=='+'||temp=='-'||temp=='*'||temp=='/')
{
show_equation.deleteCharAt(show_equation.length()-1);
show_equation.append("*");
}
else
show_equation.append("*");
result.setText(show_equation);
result.setSelection(result.getText().length());
}
}
});
//除号按钮监听器
div.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//判断用户是否输入了内容
if(!(show_equation.toString().equals(""))) {
signal=0;
char temp=show_equation.charAt(show_equation.length()-1);
if(temp=='+'||temp=='-'||temp=='*'||temp=='/')
{
show_equation.deleteCharAt(show_equation.length()-1);
show_equation.append("/");
}
else
show_equation.append("/");
result.setText(show_equation);
result.setSelection(result.getText().length());
}
}
});
}
protected boolean operatorPriorityCompare(char operator1,char operator2)
{
//o1，o2设置运算优先级
int o1=0;
int o2=0;
switch (operator1){
case '+':{o1=0;break;}
case '-':{o1=0;break;}
case '*':{o1=1;break;}
case '/':{o1=1;break;}
}
switch (operator2){
case '+':{o2=0;break;}
case '-':{o2=0;break;}
case '*':{o2=1;break;}
case '/':{o2=1;break;}
}
if(o1<=o2)
{
return false;
}
else
return true;
}
//相加
public static Double Add(Double d1,Double d2) {
if(d1==Double.NEGATIVE_INFINITY||d1==Double.POSITIVE_INFINITY||d2==Double.NEGATIVE_INFINITY||d2==Double.POSITIVE_INFINITY){
return d1+d2;
}
if(String.valueOf(d1).equals("NaN")||String.valueOf(d1).equals("NaN")){
return d1+d2;
}
BigDecimal b1 = new BigDecimal(Double.toString(d1));
BigDecimal b2 = new BigDecimal(Double.toString(d2));
return b1.add(b2).doubleValue();
}
//相减
public static Double Sub(Double d1,Double d2){
if(d1==Double.NEGATIVE_INFINITY||d1==Double.POSITIVE_INFINITY||d2==Double.NEGATIVE_INFINITY||d2==Double.POSITIVE_INFINITY){
return d1-d2;
}
if(String.valueOf(d1).equals("NaN")||String.valueOf(d1).equals("NaN")){
return d1-d2;
}
if(String.valueOf(d1).equals("NaN")||String.valueOf(d1).equals("NaN")){
return d1*d2;
}
BigDecimal b1=new BigDecimal(Double.toString(d1));
BigDecimal b2=new BigDecimal(Double.toString(d2));
return b1.subtract(b2).doubleValue();
}
//相乘
public static Double Mul(Double d1,Double d2){
if(d1==Double.NEGATIVE_INFINITY||d1==Double.POSITIVE_INFINITY||d2==Double.NEGATIVE_INFINITY||d2==Double.POSITIVE_INFINITY){
return d1*d2;
}
if(String.valueOf(d1).equals("NaN")||String.valueOf(d1).equals("NaN")){
return d1*d2;
}
BigDecimal b1=new BigDecimal(Double.toString(d1));
BigDecimal b2=new BigDecimal(Double.toString(d2));
return b1.multiply(b2).setScale(8).doubleValue();
}
//相除
public static Double Div(Double d1,Double d2){
if(d1==Double.NEGATIVE_INFINITY||d1==Double.POSITIVE_INFINITY||d2==Double.NEGATIVE_INFINITY||d2==Double.POSITIVE_INFINITY){
return d1/d2;
}
if(String.valueOf(d1).equals("NaN")||String.valueOf(d1).equals("NaN")){
return d1/d2;
}
if(d1==0.0&&d2==0.0){
return Double.NaN;
}
if(d2==0.0){
return d1/d2;
}
BigDecimal b1=new BigDecimal(Double.toString(d1));
BigDecimal b2=new BigDecimal(Double.toString(d2));
return b1.divide(b2,8,BigDecimal.ROUND_HALF_UP).doubleValue();
}
protected String calculate(ArrayList equation){
Double temp2;
Double temp3;
Double result;
List operator=new ArrayList();
List<Double> operand=new ArrayList();
for(int i=0;i<equation.size();i++)
{
String temp4=(String) equation.get(i);
if(temp4.equals("+")||temp4.equals("-")||temp4.equals("*")||temp4.equals("/"))
{
if(operator.size()>0)
{
String temp5=operator.get(operator.size()-1).toString();
while(!(operatorPriorityCompare(temp4.charAt(0),temp5.charAt(0)))&&operator.size()>0)
{
operator.remove(operator.size()-1);
temp3=operand.get(operand.size()-1);
operand.remove(operand.size()-1);
temp2=operand.get(operand.size()-1);
operand.remove(operand.size()-1);
switch (temp5.charAt(0)){
case '+':{result=Add(temp2,temp3);operand.add(result);break;}
case '-':{result=Sub(temp2,temp3);operand.add(result);break;}
case '*':{result=Mul(temp2,temp3);operand.add(result);break;}
case '/':{result=Div(temp2,temp3);operand.add(result);break;}
}
if(operator.size()>0)
{
temp5=operator.get(operator.size()-1).toString();
}
else
break;
}
operator.add(temp4);
}
else
operator.add(temp4);
}
else if(temp4.equals("#"))
{
while(operator.size()>0)
{
String temp6=(String)operator.get(operator.size()-1);
operator.remove(operator.size()-1);
temp3=operand.get(operand.size()-1);
operand.remove(operand.size()-1);
temp2=operand.get(operand.size()-1);
operand.remove(operand.size()-1);
switch (temp6.charAt(0)){
case '+':{result=Add(temp2,temp3);operand.add(result);break;}
case '-':{result=Sub(temp2,temp3);operand.add(result);break;}
case '*':{result=Mul(temp2,temp3);operand.add(result);break;}
case '/':{result=Div(temp2,temp3);operand.add(result);break;}
}
}
}
else
{
if(temp4.equals("NaN")){
operand.add(Double.NaN);
}else if(temp4.equals("∞")){
operand.add(Double.POSITIVE_INFINITY);
}else{
operand.add(Double.parseDouble(temp4));
}
}
}
if(operand.get(0)==Double.NEGATIVE_INFINITY) return "-∞";
if(operand.get(0)==Double.POSITIVE_INFINITY) return "∞";
return operand.get(0).toString();
}
//当API最低版小于21时使用这个函数实现点击文本框不弹出键盘
public void disableShowInput(EditText et) {
Class<EditText> cls = EditText.class;
Method method;
try {
method = cls.getMethod("setShowSoftInputOnFocus", boolean.class);
method.setAccessible(true);
method.invoke(et, false);
} catch (Exception e) {
e.printStackTrace();
}
}
}
4.运行程序
可拓展指出：
1.程序界面美化
2.增加运算功能
个人总结：
在查看别人的实现代码过程中，学到了不少知识。同时我发现，随着Android的不断更新，许多接口以及写法都有些许改变。在运行别人的代码时，总有各种各样的问题出现，根据问题百度查找解决方法，发现一些问题其实是很久的，但随着技术的不断更新改良，一些方法得以简化，要逐渐学会去研读开发文档，找到用法。