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我想使用 ClojureScript 和 react-native 从移动应用程序将文件下载到手机存储中。文件已上传到 Amazon S3 存储桶。文件 URL 类似于https://s3.amazonaws.com/client-texastech/uploads/art_pictures-images/comma-2005-06/96acad35-7f3f-4b10-a104-5bf59b92b463/medium/image.jpg?X -Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIQETNIOQ45P7UIKQ%2F20181113%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20181113T023654Z&X-Amz-Expires=300&X-Amz-SignedHeaders=host =576787721283e1c2b0d8fd2349cd304b5f7f717491edb32d8d7ba256ef52f6a8

我找到了 react-native-fetch-blob 来做这件事。

我尝试使用它：

    (def RNFetchBlob (js/require "react-native-fetch-blob"))
    (def fetch-blob (oget RNFetchBlob "default"))
    (def fs (oget RNFetchBlob "fs"))

      (defn download-url [app-db url]
  (p/promise (fn [resolve reject]
                  (let [fs (oget fetch-blob "fs")
                      dir-path (str (oget (oget fs "dirs") "DocumentDir") "/image.png")
                      fetch-config (ocall fetch-blob "config" {
                                       :addAndroidDownloads {:useDownloadManager true :path dir-path :notification true}
                                       :Cache-Control "no-store"}) 
                      fetch-file (ocall fetch-config "fetch" "GET" url (util/get-token app-db))
                      base64 (oget fetch-blob "base64")]
                  (ocall fetch-file "then" (fn [res]
                      (.log js/console "Download file completed." res)
                      (resolve true)))
                  (ocall fetch-file "catch" (fn [res]
                        (.log js/console "Download file failed" res)
                        (resolve false)))
              #js{:timeout 600000
                  :distanceFilter 1
                  :maximumAge 1000
                  :enableHighAccuracy false}))))

下载完成。但是，我在任何文件夹中都找不到该文件。有什么问题吗？如果是这样，任何人都可以分享代码片段吗？

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2 回答 2

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最后，我能够下载该文件。问题是我将参数传递给配置调用。我们应该使用 clj->js 将 Clojure 转换为 JS。更新后的方法如下：

(defn download-image-android [app-db url image-id]
  (p/promise (fn [resolve reject]
      (let [fs (oget fetch-blob "fs")
          android-dir-path (str (oget (oget fs "dirs") "DownloadDir") "/" image-id ".jpg")
          params (parse-params url)
          fetch-config (ocall fetch-blob "config" (clj->js {
                            :fileCache true
                            :addAndroidDownloads {:useDownloadManager true :path android-dir-path :notification true}})) 
          fetch-file (ocall fetch-config "fetch" "GET" url (clj->js {:Signature (:X-Amz-Signature params)
                                                                :Cache-Control "no-store"}))]
          (ocall fetch-file "then" (fn [res]
              (show-alert "Success" "Image has been saved to the phone successfully!")
              (resolve true)))
          (ocall fetch-file "catch" (fn [res]
              (show-alert "Error" "Image cannot be downloaded. Please try again!")
              (.log js/console "Download file failed" res)
              (resolve false)))
      #js{:timeout 30000
          :distanceFilter 1
          :maximumAge 1000
          :enableHighAccuracy false}))))
于 2019-02-12T08:43:48.843 回答
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如果您想从 S3 下载并显示任何图像，您可以使用带有源属性的RN Image

 [image {:source "https://your.s3.bucket/path.jpg"}]

如果它只是一个文件，那么使用rn-fetch-blob 

(defn fetch-file! [url]
  (let [result (promise-chan)]
    (-> RNFetchBlob
      (.config #js{})
      (.fetch "GET" url)
      (.then #(.text %))
      (.then #(put! result [true %]))
      (.catch #(put! result [false %])))
    result))

确保您有权访问您的 S3 文件

于 2018-10-30T12:17:59.237 回答