uniapp开发的h5页面嵌入app中，在app下载附件无法下载，在浏览器中可以下载，请教一下，帮忙看下哪里有问题呢

filePreview(fileInfo){  
    const _this = this;  

    let pkPubBlob = fileInfo.pkPubBlob  
    let fileName = fileInfo.fileName  
    let xtoken = utils.cache.getItem("token");  
    let fileUrl = `${PREVIEWURL}/app/doc/downloadFile?pkPubBlob=${pkPubBlob}&fileName=${fileName}&xquant-token=${xtoken}`  
    console.log(fileUrl);  
    // if(!this.fileAllowToView(fileName).length) {  
    //  uni.showToast({  
    //      title: '该文件类型不支持手机在线查看，请切换至电脑端',  
    //      icon: "none",  
    //      duration: 4000  
    //  });  
    //  return false;  
    // }  
    if(_this.isIMG(fileName).length){  
        uni.previewImage({  
            urls: [fileUrl],  
        });  
    } else {  
        // #ifdef APP-PLUS  
        uni.showToast({  
            title: "APP-附件下载",  
            icon: "none",  
            duration: 3000  
        });  
        _this.openRemoteFile(fileUrl)  
        // #endif  
        // #ifndef APP-PLUS  
        uni.showToast({  
            title: "H5-附件下载",  
            icon: "none",  
            duration: 3000  
        });  
        _this.openFile(encodeURI(fileUrl))  
        // #endif  
    }  
},  
//打开本地文件  
openRemoteFile(url) {  
    uni.showLoading({  
        title: '正在打开文件...',  
        mask: true  
    });  
    var dtask = plus.downloader.createDownload(encodeURI(url), {  
        method: "GET"  
    }, function(d, status) {  
        if (status == 200) {  
            plus.runtime.openFile(d.filename, {}, function(e) {  
                uni.hideLoading();  
                console.log("无法打开此文件：" + e.emssage, "查看附件");  
            });  
            uni.hideLoading();  
        } else {  
            uni.hideLoading();  
            console.log("文件打开失败: " + status, "查看附件");  
        }  
    });  
    dtask.start();  
},  
openFile(url) {  
    console.log("H5");  
    var link = document.createElement('a');  
    link.href = url;  
    link.target = '_blank';  
    link.click();  
    link.remove();  
},