问题描述

想通过按钮触组件，组件负责发生成二维码。通过尝试，可以在本地缓存文件中成功生成临时图片，但是没有成功绘制此图片，小程序中调试报错：image load faild null。

以下是我的代码

const QRCode = require('../../utils/qrcode.js')
Component({
    properties: {
        qrCodeId: String
    },
    data: {
        canvasHidden: false,
        imagePath: ""
    },
    ready: function (options) {
        var that = this;
        var initUrl = 'https://www.sfatpaper.com?qrcode=' + this.properties.qrCodeId;
        that.createQrCode(initUrl, 'mycanvas', 170, 170);
    },
    createQrCode: function(url, canvasId, cavW, cavH) {
        var that = this;
        QRCode.api.draw(url, canvasId, cavW, cavH);
        setTimeout(() => {
            that.canvasToTempImage();
        }, 500);
    },
    canvasToTempImage: function() {
        var that = this;
        swan.canvasToTempFilePath({
            canvasId: 'mycanvas',
            success: function(res) {
                var tempFilePath = res.tempFilePath;
                that.setData({
                    imagePath: tempFilePath,
                    canvasHidden: true
                });
            },
            fail: function(res) {
                console.log(res);
            }
        });
    }
});

请问此问题是为什么呢？还望在这里得到答案，谢谢诸位耐心的解答！