闲来无事，用android做一个计算器玩玩，想着做一个私密空间，表面是计算器，按下原先设定的算式后可以跳转到私密界面，当想想有些费事，以后若还有闲散时间，再来实现。
我实现了更完善的计算器，功能更多，逻辑更完善，欢迎访问！点击这里
界面是这样的，采用了GridLayout布局，很容易实现。代码如下
<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:columnCount="4"
android:layout_gravity="center"
android:orientation="horizontal">
<TextView
android:id="@+id/contentText"
android:textSize="16sp"
android:text="@string/defaultText"
android:layout_gravity="fill"
android:maxLines="1"
android:layout_marginTop="55sp"
android:paddingRight="15sp"
android:layout_columnSpan="4"
android:gravity="right"/>
<Button
android:id="@+id/bt1"
android:text="@string/bt1"
android:textSize="15sp"
android:layout_gravity="fill"
android:layout_marginTop="25sp"
android:layout_marginRight="5sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt2"
android:text="@string/bt2"
android:textSize="15sp"
android:layout_gravity="fill"
android:layout_marginTop="25sp"
android:layout_marginBottom="5sp"
android:layout_marginRight="5sp"
android:layout_columnSpan="2"
/>
<Button
android:id="@+id/bt18"
android:text="@string/bt18"
android:textSize="15sp"
android:layout_marginTop="25sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt3"
android:text="@string/bt3"
android:textSize="15sp"
android:layout_marginRight="5sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt4"
android:text="@string/bt4"
android:textSize="15sp"
android:layout_marginRight="5sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt5"
android:text="@string/bt5"
android:textSize="15sp"
android:layout_marginRight="5sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt6"
android:text="@string/bt6"
android:textSize="15sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt7"
android:text="@string/bt7"
android:textSize="15sp"
android:layout_marginRight="5sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt8"
android:text="@string/bt8"
android:textSize="15sp"
android:layout_marginRight="5sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt9"
android:text="@string/bt9"
android:textSize="15sp"
android:layout_marginRight="5sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt10"
android:text="@string/bt10"
android:textSize="15sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt11"
android:text="@string/bt11"
android:textSize="15sp"
android:layout_marginRight="5sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt12"
android:text="@string/bt12"
android:textSize="15sp"
android:layout_marginRight="5sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt13"
android:text="@string/bt13"
android:textSize="15sp"
android:layout_marginRight="5sp"
android:layout_marginBottom="5sp"
/>
<Button
android:id="@+id/bt14"
android:text="@string/bt17"
android:textSize="15sp"
android:layout_gravity="fill"
android:layout_rowSpan="2"
/>
<Button
android:id="@+id/bt15"
android:text="@string/bt15"
android:textSize="15sp"
android:layout_marginRight="5sp"
/>
<Button
android:id="@+id/bt16"
android:text="@string/bt16"
android:textSize="15sp"
android:layout_marginRight="5sp"
/>
<Button
android:id="@+id/bt17"
android:text="@string/bt14"
android:textSize="15sp"
android:layout_marginRight="5sp"
/>
</GridLayout>对应的string.xml代码文件如下：
<resources>
<string name="app_name">简易计算器</string>
<string name="bt1">CE</string>
<string name="bt2">Backspace</string>
<string name="bt3">7</string>
<string name="bt4">8</string>
<string name="bt5">9</string>
<string name="bt6">*</string>
<string name="bt7">4</string>
<string name="bt8">5</string>
<string name="bt9">6</string>
<string name="bt10">-</string>
<string name="bt11">1</string>
<string name="bt12">2</string>
<string name="bt13">3</string>
<string name="bt14">+</string>
<string name="bt15">0</string>
<string name="bt16">.</string>
<string name="bt17">=</string>
<string name="bt18">/</string>
<string name="defaultText">输入算式进行计算</string>
</resources>到这里，计算器的界面布局已经实现，下面就是最重要的逻辑处理了。逻辑处理分为两部分：算式输入的强制排错和算式的结果计算。算式输入的强制排错就是对算式输入的规范，比如不能连续输入++，**，23.23.23，之类的无效算式;算式的结果计算就是根据输入的算式（我将输入的算式保存在string对象里）计算出结果。代码如下：
package com.example.ffy.other;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity implements View.OnClickListener{
private Button[] buttons = new Button[18];
private int[] ids = new int[]{R.id.bt1,R.id.bt2,R.id.bt3,R.id.bt4,R.id.bt5,R.id.bt6,R.id.bt7,
R.id.bt8,R.id.bt9,R.id.bt10,R.id.bt11,R.id.bt12,R.id.bt13,R.id.bt14,R.id.bt15,R.id.bt16,R.id.bt17,R.id.bt18
};
private TextView textView;
private String expression = "";
private boolean end = false;
private int countOperate=2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.calculator);
for(int i=0;i<ids.length;i++){
buttons[i] = (Button)findViewById(ids[i]);
buttons[i].setOnClickListener(this);
}
textView = (TextView)findViewById(R.id.contentText);
}
//点击事件，强制排错
public void onClick(View view) {
int id = view.getId();
Button button = (Button)view.findViewById(id);
String current = button.getText().toString();
if(end){ //如果上一次算式已经结束，则先清零
expression = "";
end = false;
}
if(current.equals("CE")){ //如果为CE则清零
expression = "";
countOperate=0;
}else if(current.equals("Backspace")){ //如果点击退格
if(expression.length()>1){ //算式长度大于1
expression = expression.substring(0,expression.length()-1);//退一格
int i = expression.length()-1;
char tmp = expression.charAt(i); //获得最后一个字符
char tmpFront = tmp;
for(;i>=0;i--){ //向前搜索最近的 +-*/和.，并退出
tmpFront = expression.charAt(i);
if(tmpFront=='.'||tmpFront=='+'||tmpFront=='-'||tmpFront=='*'||tmpFront=='/'){
break;
}
}
// Toast.makeText(this, "tmp = "+tmp, Toast.LENGTH_SHORT).show();
if(tmp>='0'&&tmp<='9'){ //最后一个字符为数字，则识别数赋值为0
countOperate=0;
}else if(tmp==tmpFront&&tmpFront!='.') countOperate=2; //如果为+-*/，赋值为2
else if(tmpFront=='.') countOperate=1; //如果前面有小数点赋值为1
}else if(expression.length()==1){
expression = "";
}
}else if(current.equals(".")){
if(expression.equals("")||countOperate==2){
expression+="0"+current;
countOperate = 1; //小数点按过之后赋值为1
}
if(countOperate==0){
expression+=".";
countOperate = 1;
}
}else if(current.equals("+")||current.equals("-")||current.equals("*")||current.equals("/")){
if(countOperate==0){
expression+=current;
countOperate = 2; // +-*/按过之后赋值为2
}
}else if(current.equals("=")){ //按下=时，计算结果并显示
double result = (double) Math.round(count()*100)/100;
expression+="="+result+"(结果只保留两位小数)";
end = true; //此次计算结束
}
else{//此处是当退格出现2+0时，用current的值替代0
if(expression.length()>=1){
char tmp1 = expression.charAt(expression.length()-1);
if(tmp1=='0'&&expression.length()==1){
expression = expression.substring(0,expression.length()-1);
}
else if(tmp1=='0'&&expression.length()>1){
char tmp2 = expression.charAt(expression.length()-2);
if(tmp2=='+'||tmp2=='-'||tmp2=='*'||tmp2=='/'){
expression = expression.substring(0,expression.length()-1);
}
}
}
expression+=current;
if(countOperate==2||countOperate==1) countOperate=0;
}
// Toast.makeText(this, "countOperate:"+countOperate, Toast.LENGTH_SHORT).show();
textView.setText(expression); //显示出来
}
//计算逻辑，求expression表达式的值
private double count(){
double result=0;
double tNum=1,lowNum=0.1,num=0;
char tmp=0;
int operate = 1; //识别+-*/，为+时为正数，为-时为负数，为×时为-2/2,为/时为3/-3;
boolean point = false;
for(int i=0;i<expression.length();i++){ //遍历表达式
tmp = expression.charAt(i);
if(tmp=='.'){ //因为可能出现小数，此处进行判断是否有小数出现
point = true;
lowNum = 0.1;
}else if(tmp=='+'||tmp=='-'){
if(operate!=3&&operate!=-3){ //此处判断通用，适用于+-*
tNum *= num;
}else{ //计算/
tNum /= num;
}
// Toast.makeText(this, "tNum = "+tNum, Toast.LENGTH_SHORT).show();
if(operate<0){ //累加入最终的结果
result -= tNum;
}else{
result += tNum;
}
operate = tmp=='+'?1:-1;
num = 0;
tNum = 1;
point = false;
}else if(tmp=='*'){
if(operate!=3&&operate!=-3){
tNum *= num;
}else{
tNum /= num;
}
operate = operate<0?-2:2;
point = false;
num = 0;
}else if(tmp=='/'){
if(operate!=3&&operate!=-3){
tNum *= num;
}else{
tNum /= num;
}
operate = operate<0?-3:3;
point = false;
num = 0;
}else{
//读取expression中的每个数字，doube型
if(!point){
num = num*10+tmp-'0';
}else{
num += (tmp-'0')*lowNum;
lowNum*=0.1;
}
}
}
//循环遍历结束，计算最后一个运算符后面的数
if(operate!=3&&operate!=-3){
tNum *= num;
}else{
tNum /= num;
}
// Toast.makeText(this, "tNum = "+tNum, Toast.LENGTH_SHORT).show();
if(operate<0){
result -= tNum;
}else{
result += tNum;
}
//返回最后的结果
return result;
}
}