我已经解决了这个问题。如果有人正在寻找方法，在这儿呢。这不是上传，因为它没有权限读取的文件。我给在AndroidManifest.xml中的权限和它的工作。

I have solved this issue. If someone is looking for the method, here it is. It was not uploading because it didn't have permission to read the file. I gave the permissions in AndroidManifest.xml and it worked.

权限在AndroidManifest.xml中

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

工作code

TransferManager transferManager = new TransferManager(provider);
String bucket = "uni-cloud";
File file = new File("//sdcard//Download//cw.pdf");
if(file.exists())
{
    Log.e(TAG,"File found " + file.getName());
}
else {
    Log.e(TAG,"File not found");
}

Upload upload = transferManager.upload(bucket, file.getName(), file);
while (!upload.isDone()){
    //Show a progress bar...
    TransferProgress transferred = upload.getProgress();
    Toast.makeText(this, "Uploading... ", Toast.LENGTH_LONG).show();
    Log.i("Percentage", "" +transferred.getPercentTransferred());
}

Toast.makeText(this, "Uploaded", Toast.LENGTH_LONG).show();