微信小程序开发(2) 计算器

在这篇微信小程序开发教程中，我们将介绍如何使用微信小程序开发计算器功能。

本文主要分为两个部分，小程序主体部分及计算器业务页面部分

一、小程序主体部分

一个小程序主体部分由三个文件组成，必须放在项目的根目录，如下：

1. 小程序逻辑

App({
  onLaunch: function() {
    // Do something initial when launch.
  },
  onShow: function() {
      // Do something when show.
  },
  onHide: function() {
      // Do something when hide.
  },
  globalData: 'I am global data'
})

2. 小程序公共设置

{
  "pages": [
    "page/index/index"
  ],
  "window": {
    "navigationBarBackgroundColor": "#000",
    "backgroundColor": "#000",
    "navigationBarBackgroundColor": "#000"
  },
  "networkTimeout": {
    "request": 10000,
    "connectSocket": 10000,
    "uploadFile": 10000,
    "downloadFile": 10000
  },
  "debug": true
}

二、计算器页面部分

计算器页面主要由以下文件组成。

1. 计算器页面结构

页面结构分为2个主要部分：显示区和键盘区

其中键盘区又分功能键、数字键，及运算键，页面结构如下

<template name="calculator-key">
  <button hover-start-time="{{5}}" hover-stay-time="{{20}}" 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' : 'AC'}}"/>
        <template is="calculator-key" data="{{className: 'key-sign', display: '±'}}"/>
        <template is="calculator-key" data="{{className: 'key-percent', display: '%'}}"/>
      </view>
      /*sdf*/
      <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>

2. 计算器样式表

样式代码如下所示

@import "reset.wxss";

page {
  font: 100 14px 'Roboto';
}

.calculator {
  width: 100%;
  height: 100vh;
  background: black;
  position: relative;
  box-shadow: 0px 0px 20px 0px #aaa;
  display: flex;
  flex-direction: column;
  box-sizing: border-box;
}

.calculator-display {
  background: #1c191c;
  flex:;
}

/*TODO:解决文本垂直居中问题*/
.calculator-display-text {
  padding: 0 30px;
  font-size: 6em;
  color: white;
  text-align: right;
}

.calculator-keypad {
  display: flex;
}

.calculator .function-keys {
  display: flex;
}

.calculator .digit-keys {
  background: #e0e0e7;
  display: flex;
  flex-direction: row;
  flex-wrap: wrap-reverse;
}

.calculator-key-hover {
  box-shadow: inset 0px 0px 25vw 0px rgba(0,0,0,0.25);
}

.calculator-key {
  display: block;
  width: 25vw;
  height: 25vw;
  line-height: 25vw;
  border-top: 1px solid #777;
  border-right: 1px solid #666;
  text-align: center;
  box-sizing: border-box;
}

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

.calculator .digit-keys .calculator-key {
  font-size: 2.25em;
}

.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: white;
  border-right:;
  font-size: 3em;
}

.calculator .function-keys {
  background: linear-gradient(to bottom, rgba(202,202,204,1) 0%, rgba(196,194,204,1) 100%);
}

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

.input-keys {
  width: 75%;
}

.operator-keys {
  width: 25%;
}

3、 计算器页面逻辑处理

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
        })
      }
    }
  }
})

三、程序效果图

四、源代码下载

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源代码使用方法，请参考  微信小程序开发入门教程