保存blob错误的本地文本不能将对象转换为[索引1处的B

Question

我有一个Nativescript角应用程序，从Rails服务器下载一个pdf作为Blob Uint8Array格式，当我试图保存它时，我得到以下错误；

JS: /data/user/0/com.asset.management/files/result.pdf
JS: ERROR Error: Uncaught (in promise): Error: Cannot convert object to [B at index 1
JS: Error: Cannot convert object to [B at index 1
JS:     at file: node_modules/@nativescript/core/file-system/file-system-access.android.js:215:0
JS:     at new ZoneAwarePromise (file: node_modules/nativescript-angular/zone-js/dist/zone-nativescript.js:902:0)
JS:     at FileSystemAccess.push.../node_modules/@nativescript/core/file-system/file-system-access.js.FileSystemAccess.writeAsync (file: node_modules/@nativescript/core/file-system/file-system-access.android.js:213:0)
JS:     at file: node_modules/@nativescript/core/file-system/file-system.js:240:0
JS:     at new ZoneAwarePromise (file: node_modules/nativescript-angular/zone-js/dist/zone-nativescript.js:902:0)
JS:     at File.push.../node_modules/@nativescript/core/file-system/file-system.js.File.write (file: node_modules/@nativescript/core/file-system/file-system.js:231:0)
JS:     at SafeSubscriber._next (file: src/app/assets/assets.component.ts:92:25)
JS:     at SafeSubscriber.push.../node_modules/rxjs/_esm5/internal/Subscriber.js.SafeSubscriber.__tryOrUn...

这是密码；

        this.http.get(url, { responseType: 'blob' })
            .subscribe(data => {

                const documentsFolder = knownFolders.documents();
                const destination = path.join(documentsFolder.path, 'result.pdf');
                const file = File.fromPath(destination);

                file.write(data);
                this.pdfUrl = file.path;
            });

我试图保存这个文件，这样我就可以用nativescript-pdf-view插件来查看它。

更新:检查文件系统

我已经访问了我的模拟器，并找到了它应该写入文件的目录，它就在那里，但是它的大小是零字节。

: adb root
: adb shell
: su
: cd /data/user/0/com.asset.management/files
: ls -al

Results
: -rw------- 1 u0_a78 u0_a78    0 2020-05-12 14:20 result.pdf

注意:我试着将一些基本文本写到一个文件中，这是有效的。因此，它必须与“数据”的格式有关。

更新:调试器中“数据”的结果

Blob {_buffer: Uint8Array(23251), _size: 23251, _type: "application/pdf", Symbol(Symbol.toStringTag): "Blob"}
size: 23251
type: "application/pdf"
Symbol(Symbol.toStringTag): "Blob"
_buffer: Uint8Array(23251) [37, 80, 68, 70, 45, 49, 46, 52, 10, 49, 32, 48, 32, 111, 98, 106, 10, 60, 60, 10, 47, 84, 105, 116, 108, 101, 32, 40, 254, 255, 41, 10, 47, 67, 114, 101, 97, 116, 111, 114, 32, 40, 254, 255, 0, 119, 0, 107, 0, 104, 0, 116, 0, 109, 0, 108, 0, 116, 0, 111, 0, 112, 0, 100, 0, 102, 0, 32, 0, 48, 0, 46, 0, 49, 0, 50, 0, 46, 0, 53, 41, 10, 47, 80, 114, 111, 100, 117, 99, 101, 114, 32, 40, 254, 255, 0, 81, 0, 116, 0, …]
_size: 23251
_type: "application/pdf"
__proto__: Object

更新:创建游乐场示例

https://play.nativescript.org/?template=play-ng&id=gA70GM&v=2

更新:在后端上发送

这是我在示例中用来发送test.pdf的Rails代码。在我的实际应用程序中，它是生成的pdf，而不是文件。不过，发送的效果是一样的。

  def index

    respond_to do |format|
      format.html
      format.pdf do
        send_file("#{Rails.root}/public/test.pdf")
      end
    end
  end

Answer 1

我想这应该是由于{N}中的Blob填充。可以将Blob对象转换为Byte数组。

   this.http.get(url, { responseType: 'blob' })
        .subscribe(data => {

            const documentsFolder = knownFolders.documents();
            const destination = path.join(documentsFolder.path, 'result.pdf');
            const file = File.fromPath(destination);

            const blob = (Array as any).create("byte", data.size);
            for (let i = 0; i < blob.length; i++) {
                blob[i] = (data as any)._buffer[i];
            }

            file.write(blob);
            this.pdfUrl = file.path;
        });