If the file was copied to another folder, you can't get a preview of the image.

[ike20013]

Hello, I found this problem: If I copied the image to another folder, I can't get the preview via remotePath. As I understand it, nextcloud preview images are taken through the ID, not through the path, but you do not have the implementation of getting the ID. How can I fix this myself in my code, or you need to fix it on your side?

[provokateurin]

Can you provide a minimal example to demonstrate the problem?

[ike20013]

In short, I made a copy of the image from one folder to another, using "copy", and because of this, getPreview and getThumbnail return an empty uint8list array, I also checked the link that your script generates, there I get [], an empty array, apparently this happens because nextcloud itself takes a preview of the image by the file ID, and not by its remote path, as it is implemented in you. Let's say I had a picture on the path "files/user/pic.png", getpreview command get Uint8List array and output preview, make a copy of the image in the path "file/user/folder/pic.png" and the getPreview command returns [].

When I tried to find out how to get a preview in nextcloud itself on the Web, through viewing elements, I found this: "style=" background-image: url ("/core/preview?fileId=1537&c=cd6948ea3014bdb476b727556125cae9&x=238&y=238&forceIcon=0");"". As I see here, the preview of the image is taken through the file ID, in the Nextcloud API in "Listing Files" there is a line "<oc:fileid/>", I think that you need to get previews for images through this ID.

Thank you for paying attention to this problem, I am waiting for your response.

[provokateurin]

Ok I understand now. I'll check how to fix it in a the next days

[ike20013]

For preview link look like this: http://$_baseUrl/core/preview?fileId=$picture_id&x=$width&y=$height In this link you get Base64 String in sources. I find this in DevTools "Network" in my browser. You need take id from your parse XML. I can advise you to use XML2JSON package to translate the XML tree to JSON array, and from there people could map what you need or what would your package parse through the model, I don't know how to do it correctly, I just think that parsing XML manually is time-consuming, thank you for listening.

[fkleon]

I've added support for retrieving oc:fileid and oc:id to WebDavClient in #14 which should allow you to get a file ID for a path.

It should be fairly easy to change the PreviewClient to accept these file IDs.

[ike20013]

Yes, I see, thank you very much for your work. But in the preview/client.dart file, the preview image is still being searched via remotePath, so it should be, and instead of it, I just need to substitute the file ID? Just above I threw off an example of the link as it looks. There in the line is fileId=$id, you have in _getPreviewUrl file=${Uri.encodeQueryComponent(remotePath)}

  String _getPreviewUrl(String remotePath, int width, int height) {
    return '$_baseUrl/index.php/core/preview.png?
file=${Uri.encodeQueryComponent(remotePath)}
&x=$width&y=$height&a=1&mode=cover&forceIcon=0';
  }

and my option $_baseUrl/index.php/core/preview?fileId=$picture_id&x=$width&y=$height&a=1&mode=cover&forceIcon=0

[fkleon]

Yes, using the fileId URL parameter instead of file sounds exactly right.

For proper support the PreviewClient implementation would need to be changed to accept either fileId exclusively, or optionally for the getPreview, getPreviewStream and getThumbnail methods.

[vauvenal5]

I think i will have some time to fix this by end of the week, since I submitted the original PreviewClient. I suggest supporting both based on this post https://help.nextcloud.com/t/getting-image-preview-with-android-library-or-via-webdav/75743/2

@ike20013 were you able to find any official documentation regarding the preview api?

[ike20013]

Hello, when trying to build a project, I get the following error, how can I fix it?

[vauvenal5]

@ike20013 I am not able to reproduce your issue. I wrote a test and executed it against a clean Nextcloud Docker container.

You can find the test here: https://github.com/vauvenal5/dart-nextcloud/blob/1e8ff28293fb1c26ce84009d900cc285e943568f/test/nextcloud_test.dart#L482 And the test config was as follows:

{
    "host": "http://localhost:8080",
    "username": "test",
    "password": "test",
    "shareUser": "yaga_share",
    "testDir": "files/test",
    "image": "Photos/Steps.jpg",
    "image_target": "Steps.jpg"
}

Still though it might be a good idea to offer both options, id and path, for requesting previews. :thinking:

[ike20013]

This error appears regardless of what I write, as if there is simply no buildDocument, I do not know why this happens, everything that you did in the new version is very cool, I just do not know why I have such a problem. I threw the project without the build folder on another computer and tried to run the project, but got this error, I did pubget, flutter clean, gradlew clean, but nothing helped

UPD: I do not know how, but I just deleted dependencies and added it again and everything worked:D

[ike20013]

I also want to add that I already gave you an example of how to get a preview of an image by ID. Since I described the problem that getting a preview of the image goes through the ID of the file, I found out when I tested the web version of nextcloud. Just if you do it through the image path, there is a problem that if you copy the image to different folders, you can get a preview only by the main path of the image. Link: http://$_baseUrl/core/preview?fileId=$picture_id&x=$width&y=$height&forceIcon=0 Maybe I can somehow get a preview through this link for the functionality that is now, or I need to have a separate function for this?

[vauvenal5]

I think, I am beginning to grasp what your issue is, you do not have the new path, correct? You have the path to a image and are showing a preview for this image, for example "files/user/pic.png". Then somebody moves the image on the server to a new directory, for example "files/user/folder/pic.png", and you lose your preview because you do not have the new path, correct?