Develop Reference

Android unable to understand kotlin function

I am not very well versed with Kotlin and I am preferring Java over Kotlin while learning Android. But I am stuck at a piece of code which is as follows:
private fun getOutputDirectory(): File {
val mediaDir = externalMediaDirs.firstOrNull()?.let {
File(it, resources.getString(R.string.app_name)).apply { mkdirs() } }
return if (mediaDir != null && mediaDir.exists())
mediaDir else filesDir
}
The following function is called in onCreate method as var outputDirectory: File = getOutputDirectory();
Can you please help me convert the code into Java and in understanding it?
Thank you.

private File getOutputDirectory() {
File mediaDir = null;
if (getExternalMediaDirs().size > 0) {
mediaDir = new File(getExternalMediaDirs()[0], getResources().getString(R.string.app_name));
mediaDir.mkdirs();
}
return if (mediaDir != null && mediaDir.exists())
mediaDir
else
filesDir
}

Here is the process on how to convert Kotlin code to Java code.
https://www.geeksforgeeks.org/how-to-convert-kotlin-code-to-java-code-in-android-studio/
But I suggest you to learn Kotlin as it is faster and preferred for Android app development.

How to Detect Multiple Images with AR core

I'm trying out detecting multiple augmented images with AR core, with
https://developers.google.com/ar/develop/java/augmented-images/guide
and other online tutorials. Currently, I have the database setup and loaded with images. However
Collection<AugmentedImage> augmentedImages = frame.getUpdatedTrackables(AugmentedImage.class);
did not seem to capture and match the feature points of my images in my db.
Can you advise me about what I need to do?
I have set up and loaded multiple images from db. The app is able to detect only 1 image previously. However, after tweaking my code to detect multiple images, it did not work properly.
Tried researching and debugging however, still unable to solve it.
private void onUpdateFrame(FrameTime frameTime)
{
Frame frame = arFragment.getArSceneView().getArFrame();
Collection<AugmentedImage> augmentedImages = frame.getUpdatedTrackables(AugmentedImage.class);
for (AugmentedImage augmentedImage : augmentedImages)
{
int i =augmentedImages.size();
Log.d("NoImage",""+i);
if (augmentedImage.getTrackingState() == TrackingState.TRACKING)
{
if (augmentedImage.getName().contains("img1") && !modelAdded)
{
renderObject(arFragment, augmentedImage.createAnchor(augmentedImage.getCenterPose()),R.raw.car);
modelAdded = true;
}
else if (augmentedImage.getName().contains("img2") && !modelAdded)
{
renderObject(arFragment, augmentedImage.createAnchor(augmentedImage.getCenterPose()), R.raw.car);
modelAdded = true;
}
else if (augmentedImage.getName().contains("img3") && !modelAdded)
{
renderObject(arFragment, augmentedImage.createAnchor(augmentedImage.getCenterPose()), R.raw.car);
modelAdded = true;
}
}
}
}

Android Rename File using Google Drive REST API v3?

How do I rename a file using the Google Drive REST API on Android? I have searched the internet however I could, but I can't find how to do this.
I am trying to write a sync method that moves and renames the cloud files if it detects that the local copy has been moved or renamed:
void syncMetadataOnly (com.google.api.services.drive.model.File cloud,
java.io.File local) throws IOException {
Workspace.FINF fileInfo = Workspace.getFileInfo (this, local); // Just my metadata object.
Map<String, String> appProperties = cloud.getAppProperties ();
// We keep track of the last rename and move in our private app properties:
long cloudLastRename = appProperties.containsKey ("last-rename") ?
Long.valueOf (appProperties.get ("last-rename")) : 0;
long cloudLastMove = appProperties.containsKey ("last-move") ?
Long.valueOf (appProperties.get ("last-move")) : 0;
boolean needUpdate = false;
boolean needName = false;
boolean needMove = false;
if (fileInfo.lastRename > cloudLastRename) {
// The file was renamed locally since the last sync.
needName = true;
needUpdate = true;
} else fileInfo.title = cloud.getName ();
String oldRecognizedParent = null;
if (fileInfo.lastMove > cloudLastMove) {
// The file was moved to a different folder locally since the last sync.
oldRecognizedParent = getFirstKnownParentId (cloud); // May be null, if not found.
needMove = true;
needUpdate = true;
}
if (needUpdate) {
cloud.setAppProperties (appProperties);
Drive.Files.Update update = mDriveService.files ().update (fileInfo.driveResourceId, null);
if (needName) update.set /// How do I rename the file?
if (needMove) {
if (oldRecognizedParent != null)
update.setRemoveParents (oldRecognizedParent);
update.setAddParents (fileInfo.driveParentId); // Set to the NEW parent's ID.
}
com.google.api.services.drive.model.File result = update.execute ();
}
}
The closest answer I have found is this, but do I really have to use raw HTTP for this?

Java Jackson DeserializationFeature

I have problem with Jackson and DeserializationFeature. From WebService I get JSON field like:
"location":null,
OR
"location":{
"code":"YYYYYY",
"label":"XXXXXX"
},
When I try get code or label eg.
project.getLocation().getCode();
Java return NullPointerException.
My current code is written like eg. and its work fine.
if (project.getLocation() != null) {
location_code = project.getLocation().getCode();
location_label = project.getLocation().getLabel();
} else {
location_code = null;
location_label = null;
}
Which option of DeserializationFeature is right for this problem?

Not sure about DeserializationFuture option, but simple null check could do the job:
String code = null;
Location location = project.getLocation(); // maybe, some yours location type
if (location != null) {
code = location.getCode();
}

Fastest/shortest way to the root folders?

I'm using Google Drive SDK v2 on Android to get the list of root folders. Currently I see these required steps - which seem to load forever. Is there no faster way?
I tried to use the search with the q= parameter but I don't get it to work (FileList vs. Files.List) - different API levels?
FileList files = drive.files().list().setQ("'root' in parents and mimeType='application/vnd.google-apps.folder' and trashed=false");
This is what I do currently:
About about = drive.about().get().execute();
if (about != null) {
ChildList childList = drive.children().list(about.getRootFolderId()).execute();
if (childList != null) {
List<ChildReference> listChildReference = childList.getItems();
for (ChildReference childReference : listChildReference) {
File file = drive.files().get(childReference.getId()).execute();
if (file != null) {
String fileExtension = file.getFileExtension();
String mimeType = file.getMimeType();
if (mimeType != null
&& mimeType.equals("application/vnd.google-apps.folder")
&& (fileExtension == null || fileExtension.equals(""))) {
Log.d(this.getClass().getName(), file.getTitle());
}
}
}
}
}
What's the fastest for an Android app?
Thanks in advance.

My personal opinion is avoid the Drive SDK and call the REST API directly. It's a fairly simple API, and the way the documentation is structured, you are forced to understand it anyway in order to use the SDK. You have the benefit that if something doesn't work, you can directly compare your app with what's happening on the wire and resolve any problems.

Found it:
#Override
protected ArrayList<File> doInBackground(final Void... voids) {
ArrayList<File> result = new ArrayList<File>();
Files.List request = null;
boolean ok = true;
do {
try {
request = drive
.files()
.list()
.setMaxResults(200)
.setQ("'root' in parents and mimeType='application/vnd.google-apps.folder' and trashed=false");
FileList files = request.execute();
result.addAll(files.getItems());
request.setPageToken(files.getNextPageToken());
} catch (IOException exception) {
ok = false;
}
} while (ok && request.getPageToken() != null && request.getPageToken().length() > 0);
return result;
}