微信小程序实现计算器小功能

微信小程序现在越来越火爆了，我也看到很多在校大学生都在自学了，那些专门从事APP开发，网页开发的工作者更是看到了小程序的前景，在小程序领域也掺上一脚，本人也是自学小程序的，初期跟很多人一样，遇到一些不懂的想问问别人，到贴吧去，一大堆广告，根本没人帮忙解决问题。

今天教一些刚入门的同学做一款计算器，如果C语言是编程的最佳入门语言，那计算器应该算得上是小程序的入门demo了，希望刚入门的同学们认真品味下面的代码，从wxml到js，再到wxss（页面的布局)，每个代码都要弄懂他的意思

废话不多说，先上效果图，这是我入门时候自己做的一款计算器，很简单，逻辑也很单一，只是我们身边最常见的计算器的逻辑，我觉得从这个demo我更深刻学习到了wxss页面的布局知识

代码附上：

app.json

 {
  "pages":[
    "pages/index/index",
    "pages/logs/logs"
  ],
  "window":
  {
  "navigationBarBackgroundColor": "#000000",
  "navigationBarTextStyle": "white",
  "navigationBarTitleText": "智能计算器"
  },
 "tabBar": {   //补充说一下，我这个tabBar是用来设置底部tab的
   "color":"#ff69b4",
   "selectedColor":"#0000ff",
   "backgroundColor":"#ffff00",
  "list": [
    {
      "pagePath": "pages/index/index",
      "text": "计 算 机"
    },
    {
      "pagePath": "pages/logs/logs",
      "text": "日志"
    },
    {
      "pagePath":"pages/logs/logs",
      "text":"回家"
    }
  ]
}
}

/*app.wxss/*

.container {
  height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: space-between;
  padding: 200rpx 0;
  box-sizing: border-box;
} 

**其中一些组件不认识的话， 建议到微信小程序官网多看几遍

index.wxml:

<template name="calculator-key">
  <button hover-start-time="{{5}}" hover-stay-time="{{100}}" hover-class="calculator-key-hover" data-key="{{className}}" class="calculator-key {{className}}">{{display}}</button>
</template>

<view class="calculator">
  <view class="calculator-display">
    <view class="calculator-display-text">{{displayValue}}</view>
  </view>
  <view class="calculator-keypad">
    <view class="input-keys">
      <view class="function-keys" catchtap="onTapFunction">
        <template is="calculator-key" data="{{className: 'key-clear', display: clearDisplay ? 'C' : 'C'}}"/>
        <template is="calculator-key" data="{{className: 'key-sign', display: '+/-'}}"/>
        <template is="calculator-key" data="{{className: 'key-percent', display: '%'}}"/>
   </view>
      <view class="digit-keys" catchtap="onTapDigit">
        <template is="calculator-key" data="{{className: 'key-0', display: '0'}}"/>
        <template is="calculator-key" data="{{className: 'key-dot', display: '●'}}"/>
        <template is="calculator-key" data="{{className: 'key-1', display: '1'}}"/>
        <template is="calculator-key" data="{{className: 'key-2', display: '2'}}"/>
        <template is="calculator-key" data="{{className: 'key-3', display: '3'}}"/>
        <template is="calculator-key" data="{{className: 'key-4', display: '4'}}"/>
        <template is="calculator-key" data="{{className: 'key-5', display: '5'}}"/>
        <template is="calculator-key" data="{{className: 'key-6', display: '6'}}"/>
        <template is="calculator-key" data="{{className: 'key-7', display: '7'}}"/>
        <template is="calculator-key" data="{{className: 'key-8', display: '8'}}"/>
        <template is="calculator-key" data="{{className: 'key-9', display: '9'}}"/>
      </view>
    </view>
    <view class="operator-keys" catchtap="onTapOperator">
        <template is="calculator-key" data="{{className: 'key-divide', display: '÷'}}"/>
        <template is="calculator-key" data="{{className: 'key-multiply', display: '×'}}"/>
        <template is="calculator-key" data="{{className: 'key-subtract', display: '−'}}"/>
        <template is="calculator-key" data="{{className: 'key-add', display: '+'}}"/>
        <template is="calculator-key" data="{{className: 'key-equals', display: '='}}"/>
    </view>
  </view>
</view>

index.js:

Page({
  data: {
    value: null, // 上次计算后的结果，null表示没有上次计算的结果
    displayValue: '0', // 显示数值
    operator: null, // 上次计算符号，null表示没有未完成的计算
    waitingForOperand: false // 前一按键是否为计算符号
  },

  onLoad: function (options) {
    this.calculatorOperations = {
      'key-divide': (prevValue, nextValue) => prevValue / nextValue,
      'key-multiply': (prevValue, nextValue) => prevValue * nextValue,
      'key-add': (prevValue, nextValue) => prevValue + nextValue,
      'key-subtract': (prevValue, nextValue) => prevValue - nextValue,
      'key-equals': (prevValue, nextValue) => nextValue
    }
  },

  /* AC操作，一下回到解放前 */
  clearAll() {
    this.setData({
      value: null,
      displayValue: '0',
      operator: null,
      waitingForOperand: false
    })
  },

  /* 仅清空当前显示的输入值 */
  clearDisplay() {
    this.setData({
      displayValue: '0'
    })
  },

  onTapFunction: function (event) {
    const key = event.target.dataset.key;

    switch (key) {
      case 'key-clear':
        if (this.data.displayValue !== '0') {
          this.clearDisplay();
        } else {
          this.clearAll();
        }

        break;

      case 'key-sign':
        var newValue = parseFloat(this.data.displayValue) * -1

        this.setData({
          displayValue: String(newValue)
        })

        break;

      case 'key-percent':
        const fixedDigits = this.data.displayValue.replace(/^-?\d*\.?/, '')
        var newValue = parseFloat(this.data.displayValue) / 100

        this.setData({
          displayValue: String(newValue.toFixed(fixedDigits.length + 2))
        });

        break;

      default:
        break;
    }
  },

  onTapOperator: function (event) {
    const nextOperator = event.target.dataset.key;
    const inputValue = parseFloat(this.data.displayValue);

    if (this.data.value == null) {
      this.setData({
        value: inputValue
      });
    } else if (this.data.operator) {
      const currentValue = this.data.value || 0;
      const newValue = this.calculatorOperations[this.data.operator](currentValue, inputValue);

      this.setData({
        value: newValue,
        displayValue: String(newValue)
      });
    }

    this.setData({
      waitingForOperand: true,
      operator: nextOperator
    });
  },

  onTapDigit: function (event) {
    const key = event.target.dataset.key; // 根据data-key标记按键

    if (key == 'key-dot') {
      // 按下点号
      if (!(/\./).test(this.data.displayValue)) {
        this.setData({
          displayValue: this.data.displayValue + '.',
          waitingForOperand: false
        })
      }
    } else {
      // 按下数字键
      const digit = key[key.length - 1];

      if (this.data.waitingForOperand) {
        this.setData({
          displayValue: String(digit),
          waitingForOperand: false
        })
      } else {
        this.setData({
          displayValue: this.data.displayValue === '0' ? String(digit) : this.data.displayValue + digit
        })
      }
    }
  }
})

index.wxss:

page {
  height:100%;
}

.calculator {
  width: 100%;
  height: 100vh;
  border:solid 1px;
  background: rgb(238, 5, 5);
  position: relative;
  box-shadow: 0px 0px 20px 0px rgb(211, 41, 41);
  display: flex;
  flex-direction: column;
  box-sizing: border-box;
}

.calculator-display {     /*显示器背景颜色*/
  background: #2c2a2c;
  flex: 1;
}

/*TODO:解决文本垂直居中问题,显示器数字颜色*/
.calculator-display-text {
  padding: 0 30px;
  font-size: 3em;
  color: rgb(245, 245, 248);
  text-align: right;
}

.calculator-keypad {
  display: flex;

}

.calculator .function-keys {
  display: flex;
  color:rgb(245, 13, 13);

}

.calculator .digit-keys {
  background: #0808f7;
  display: flex;
  flex-direction: row;
  flex-wrap: wrap-reverse;
}

.calculator-key-hover {   /*按钮按下以后的颜色*/
  box-shadow: inset 0px 0px 25vw 0px hsla(71, 90%, 48%, 0.898);
}

.calculator-key {
background-color:aqua;

  display: block;
  width: 25vw;
  height: 25vw;
  line-height: 25vw;
  border-top: 1px solid rgb(6, 245, 78);
  border-right: 1px solid rgb(19, 241, 12);
  text-align: center;
  box-sizing: border-box;
}

.calculator .function-keys .calculator-key {
  font-size: 2em;

}

.calculator .digit-keys .calculator-key {
  font-size: 3em;
}

.calculator .digit-keys .key-0 {
  width: 50vw;
  text-align: left;
  padding-left: 9vw;
}

.calculator .digit-keys .key-dot {
  padding-top: 1em;
  font-size: 0.75em;
}

.calculator .operator-keys .calculator-key {
  color: rgb(248, 165, 10);
  border-right: 0;
  font-size: 3em;
}

.calculator .function-keys {
  background: linear-gradient(to bottom, rgb(6, 6, 240) 0%, rgb(52, 5, 240) 100%);
}

.calculator .operator-keys {
  background:  linear-gradient(to bottom, rgba(252,156,23,1) 0%, rgba(247,126,27,1) 100%);
}

.input-keys {
  width: 100%;
}

.operator-keys {
  width: 100%;
}

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