Develop Reference

How to get EXIF data of an image, using Nativescript?

I'm trying to read the Exif data of an image, in Nativescript. I rely on a native Java code i saw in a tutorial:
Uri uri; // the URI you've received from the other app
InputStream in;
try {
in = getContentResolver().openInputStream(uri);
ExifInterface exifInterface = new ExifInterface(in);
// Now you can extract any Exif tag you want
// Assuming the image is a JPEG or supported raw format
} catch (IOException e) {
// Handle any errors
} finally {
if (in != null) {
try {
in.close();
} catch (IOException ignored) {}
}
}
This is my attempt to implement it with JS:
import * as application from "application";
getExif(src){//The src is a path to a file in the camera folder
const contentResolver = application.android.nativeApp.getContentResolver();
const stream = contentResolver.openInputStream(src);
const exif = new android.support.media.ExifInterface(st)//This throws an error
}
I get this error:
Error: JNI Exception occurred (SIGABRT). ======= Check the 'adb
logcat' for additional information about the error
What is the problem with my code?
Update:
app.gradle:
dependencies {
// implementation 'com.android.support:recyclerview-v7:+'
compile 'com.android.support:exifinterface:25.1.0'
}
It now actually seems to me that the error is thrown before i even try to use the plugin. It actually fails here:
const contentResolver = application.android.nativeApp.getContentResolver();
const st = contentResolver.openInputStream(src);//FAIL
I get the error i mentioned initially.

IPFS read data from network

I am working on one application, where I am using IPFS for storing and getting files.
I am using the following API for Android,
https://github.com/ligi/ipfs-api-kotlin
As per the doc, I can get data from IPFS using following code,
ipfs.get.cat("hash code of IPFS file")
but here it returns everything in string format, even if the uploaded file is Image.
How Can I know the content type of the file and download the same format?

IPFS doesn't allow to store metadata such as the content type alongside the content itself.
Something you could do in Java that worked for me:
private static String guessContentType(InputStream content) {
try {
String guessedContentType = URLConnection.guessContentTypeFromStream(content);
if (!StringUtils.isEmpty(guessedContentType)) {
return guessedContentType;
} else {
return MediaType.APPLICATION_OCTET_STREAM_VALUE;
}
} catch (IOException e) {
throw new RuntimeException("Unable to guess content type", e);
}
}

Dropbox api v2 for Android: how to get media files details?

How to get media files and their details with Dropbox API v2 for Android(Java)? I have gone through the documentation for the FileMetadata , but I couldn't find the methods to get file details like file type(e.g. music, video, photo, text, ...) , file's URL and thumbnail.
this is my folders and files list Asyntask:
//login
DbxClientV2 client = DropboxClient.getClient(accessToken);
// Get files and folder metadata from root directory
String path = "";
TreeMap<String, Metadata> children = new TreeMap<>();
try {
try {
result = client.files().listFolder(path);
arrayList = new ArrayList<>();
//arrayList.add("/");
while (true) {
int i = 0;
for (Metadata md : result.getEntries()) {
if (md instanceof DeletedMetadata) {
children.remove(md.getPathLower());
} else {
String fileOrFolder = md.getPathLower();
children.put(fileOrFolder, md);
//if (!fileOrFolder.contains("."))//is a file
arrayList.add(fileOrFolder);
if (md instanceof FileMetadata) {
FileMetadata file = (FileMetadata) md;
//I need something like file.mineType, file.url, file.thumbnail
file.getParentSharedFolderId();
file.getName();
file.getPathLower();
file.getPathDisplay();
file.getClientModified();
file.getServerModified();
file.getSize();//in bytes
MediaInfo mInfo = file.getMediaInfo();//Additional information if the file is a photo or video, null if not present
MediaInfo.Tag tag;
if (mInfo != null) {
tag = mInfo.tag();}
}
}
i++;
}
if (!result.getHasMore()) break;
try {
result = client.files().listFolderContinue(result.getCursor());//what is this for ?
} catch (ListFolderContinueErrorException ex) {
ex.printStackTrace();
}
}
} catch (ListFolderErrorException ex) {
ex.printStackTrace();
}
} catch (DbxException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
return result;

If you want media information, you should use listFolderBuilder to get a ListFolderBuilder object. You can use call .withIncludeMediaInfo(true) to set the parameter for media information, and then .start() to make the API call. The results will then have the media information set, where available.
Dropbox API v2 doesn't offer mime types, but you can keep your own file extension to mime type mapping as desired.
To get an existing link for a file, use listSharedLinks. To create a new one, use createSharedLinkWithSettings.
To get a thumbnail for a file, use getThumbnail.

How to use getClassLoader() correctly?

Here I try to use getClassLoader().getResources() to get my .model file, however it returns null. I'm not sure where goes wrong!
And when I try to print out the urls, it gives me java.lang.TwoEnumerationsInOne#5fd1900, what does this means?
public Activity(MainActivity activity) {
MainActivity activity = new MainActivity();
try {
// Open stream to read trained model from file
InputStream is = null;
// this .model file is save under my /project/app/src/main/res/
Enumeration<URL> urls = Activity.class.getClassLoader().getResources("file.model");
// System.out.println("url:"+urls);
if (urls.hasMoreElements()) {
URL element = urls.nextElement();
is = element.openStream();
}
// deserialize the model
classifier = (J48) SerializationHelper.read(is);
is.close();
} catch (Exception e) {
e.printStackTrace();
}
}

In Android, resources put under src/main/res are not visible in the class path and can only be accessed via the android resources API. Try to put the file into src/main/resources.

Download thumbnail of file from Google Drive

I can download the original file from Google Drive by using the following code :
public static InputStream downloadFile(Drive service, File file)
throws IOException {
if (file.getDownloadUrl() != null && file.getDownloadUrl().length() > 0) {
try {
HttpResponse resp = service.getRequestFactory()
.buildGetRequest(new GenericUrl(file.getDownloadUrl()))
.execute();
return resp.getContent();
} catch (IOException e) {
// An error occurred.
e.printStackTrace();
return null;
}
} else {
// The file doesn't have any content stored on Drive.
return null;
}
}
But it looks like the connection really low when downloading many files to add into the grid view.
Therefore, I need to list thumb nail instead of original file as it will be better for the connection.
Please help me how?

Use File.getThumbnail method to get the thumbnail or File.getIconLink to get the icon link.