小程序总结（二十二）- 基于Taro的长按保存图片

<Image className="qr-code" src={privateDoctor.qrCode} onLongPress={this.onSavePhoto.bind(this)}></Image>

onSavePhoto (e) {
        const qrCodePath = this.state.privateDoctor.qrCode
        const _this = this
        e.stopPropagation();
        Taro.getSetting({
            success (res) {
                if (!res.authSetting['scope.writePhotosAlbum']) {//没有授权
                    Taro.authorize({
                        scope:'scope.writePhotosAlbum',
                            success: () => {
                                _this.downloadImgToAlbum(qrCodePath);
                            },
                            fail: () => {
                                _this.setState({//显示授权层
                                    openSetting:true
                                })
                            }
                    })
                } else { //已授权
                    _this.downloadImgToAlbum(qrCodePath);
                }
            }
        })
    }

    downloadImgToAlbum (qrCodePath) {
        Taro.showToast({
            title:'正在保存，请稍等',
            icon:'none',
            duration:2000
        })
        //下载图片
        this.downloadHttpImg(qrCodePath).then((res)=>{
            this.sharePosteCanvas(res)
        })
    }
    downloadHttpImg =(httpImg) =>{
        return new Promise(((resolve) => {
            Taro.downloadFile({
                url: httpImg,
                success: (res) => {
                    if (res.statusCode ===200) {
                        resolve(res.tempFilePath)
                    } else {
                        Taro.showToast({
                            title:'图片下载失败！',
                            icon:'none',
                            duration:1000
                        })
                    }
                },
                fail: () => {
                    Taro.showToast({
                        title:'图片下载失败！',
                        icon:'none',
                        duration:1000
                    })
                }
            })
        }))
    }
    sharePosteCanvas =(imgUrl)=> {
        Taro.saveImageToPhotosAlbum({
            filePath: imgUrl,
            success () {
                Taro.showToast({
                    title:'图片已保存到相册',
                    icon:'none',
                    duration:1000
                })
            },
            fail () {
                Taro.showToast({
                    title:'图片保存失败',
                    icon:'none',
                    duration:1000
                })
            }
        })
    }