微信小程序动态生成二维码

效果图如下：

实现

wxml

<!-- 存放二维码的图片-->
<view class='container'>
    <image bindtap="previewImg" mode="scaleToFill" src="{{imagePath}}"></image>
</view>

<!-- 画布，用来画二维码，只用来站位，不用来显示-->
<view class="canvas-box">
    <canvas hidden="{{canvasHidden}}" style="width: 686rpx;height: 686rpx;background:#f1f1f1;" canvas-id="mycanvas" />
</view>

wxss

.container {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
}

.container image {
    width: 686rpx;
    height: 686rpx;
    background-color: #f9f9f9;
}

.canvas-box {
    position: fixed;
    top: 999999rpx;
    left: 0;
}

js

var QR = require("../../../lib/qrcode.js");


Page({

    /**
     * 页面的初始数据
     */
    data: {
        canvasHidden: false,
        imagePath: '',
    },

    /**
     * 生命周期函数--监听页面加载
     */
    onLoad: function(options) {
        //option为上个页面传递过来的参数
        var jiaoyanCode = 'sorry,jiaoyanCode is loss';
        if (options) {
            jiaoyanCode = options.jiaoyanCode;
        }
        console.log(jiaoyanCode);

        var size = this.setCanvasSize(); //动态设置画布大小 
        this.createQrCode(jiaoyanCode, "mycanvas", size.w, size.h);     
    },

    //适配不同屏幕大小的canvas
    setCanvasSize: function() {
        var size = {};
        try {
            var res = wx.getSystemInfoSync();
            var scale = 750 / 686; //不同屏幕下canvas的适配比例；设计稿是750宽  686是因为样式wxss文件中设置的大小
            var width = res.windowWidth / scale;
            var height = width; //canvas画布为正方形
            size.w = width;
            size.h = height;
        } catch (e) {
            // Do something when catch error
            console.log("获取设备信息失败" + e);
        }
        return size;
    },

    /**
     * 绘制二维码图片
     */
    createQrCode: function(url, canvasId, cavW, cavH) {
        //调用插件中的draw方法，绘制二维码图片
        QR.api.draw(url, canvasId, cavW, cavH);
        setTimeout(() => {
            this.canvasToTempImage();
        }, 1000);
    },

    /**
     * 获取临时缓存照片路径，存入data中
     */
    canvasToTempImage: function() {
        var that = this;
        //把当前画布指定区域的内容导出生成指定大小的图片，并返回文件路径。
        wx.canvasToTempFilePath({
            canvasId: 'mycanvas',
            success: function(res) {
                var tempFilePath = res.tempFilePath;
                console.log(tempFilePath);
                that.setData({
                    imagePath: tempFilePath,
                    // canvasHidden:true
                });
            },
            fail: function(res) {
                console.log(res);
            }
        });
    },

    /**
     * 点击图片进行预览
     */
    previewImg: function (e) {
        var img = this.data.imagePath;
        console.log(img);
        wx.previewImage({
            current: img, // 当前显示图片的http链接
            urls: [img] // 需要预览的图片http链接列表
        });
    },
})

qrcode.js 可以去 这里 下载。

详细源码请查看 https://github.com/demi520/wxapp-qrcode