Develop Reference

Writing a file to a phone's internal storage with Xamarin [duplicate]

I want to save my logs to a folder which I can access with windows explorer. For example I want to create my log in the following path
This PC\Galaxy A5 (2017)\Phone\Android\data\MyApp\files
So I tried to use Environment variables... I get such as
/data/user/...
But here i cannot see the file what I created (using code I can access the path but I want to see in the explorer).
how I can create a path like above with code?
When I tried this code
var finalPath2 = Android.OS.Environment.GetExternalStoragePublicDirectory
(Android.OS.Environment.DataDirectory.AbsolutePath);
I get the path "/storage/emulated/0/data"
and
If i use the code
var logDirectory =Path.Combine(System.Environment.GetFolderPath
(System.Environment.SpecialFolder.ApplicationData),"logs");
I get the following path like:
/data/user/0/MyApp/files/.config/logs
and
var logDirectory =Path.Combine(System.Environment.GetFolderPath
(System.Environment.SpecialFolder.MyDocuments),"logs");
"/data/user/0/IM.OneApp.Presentation.Android/files/logs"
but unfortunately I cannot access this folder by explorer....
This PC\Galaxy A5 (2017)\Phone\Android\data\MyApp\files
So how to find out this path in c# by using environments?
Update:
when I give the following path hardcoded, it creates the file where I want..
logDirectory = "/storage/emulated/0/Android/data/MyApp/files/logs";
is there any environment to create this path? I can combine 2 environments and do some string processing in order to create this path. But maybe there is an easier way?

You are looking for the root of GetExternalFilesDir, just pass a null:
Example:
var externalAppPathNoSec = GetExternalFilesDir(string.Empty).Path;
Note: This is a Context-based instance method, you can access it via the Android application context, an Activity, etc... (see the link below to the Android Context docs)
Shared storage may not always be available, since removable media can be ejected by the user. Media state can be checked using Environment.getExternalStorageState(File).
There is no security enforced with these files. For example, any application holding Manifest.permission.WRITE_EXTERNAL_STORAGE can write to these files.
re: https://developer.android.com/reference/android/content/Context#getExternalFilesDir(java.lang.String)

string docFolder = Path.Combine(System.Environment.GetFolderPath
(System.Environment.SpecialFolder.MyDocuments), "logs");
string libFolder = Path.Combine(docFolder, "/storage/emulated/0/Android/data/MyApp/files/logs");
if (!Directory.Exists(libFolder))
{
Directory.CreateDirectory(libFolder);
}
string destinationDatabasePath = Path.Combine(libFolder, "temp.db3");
db.Backup( destinationDatabasePath, "main");

ARToolkit: Created new .pat file doesn't work

I'm using ARToolkit in my Android project. I used this to help me create a new marker and everything worked fine. The file created was called marker64.pat. However, the standard pattern files that ARToolkit uses are .patt files (with the extra t). Why did it create a .pat file for me?
This .pat file doesn't seem to work, as it crashes my application just as it starts.
This is the original line of code that was already there (which works fine):
markerID = ARToolKit.getInstance().addMarker("single;Data/hiro.patt;80");
This is my changed version:
markerID = ARToolKit.getInstance().addMarker("single;Data/marker64.pat;80");
This is my marker image whilst I'm creating the marker:
Can you please let me know why, firstly, my file was created as .pat file and not a .patt file. And secondly, why this file doesn't work if it's correct.
Thanks

Android - Accessing storage locations

Ok, Quick heads up that I am new to android programming.
I have very basic experience with java from uni.
I've recently been messing around with android studio and app building for my Samsung Galaxy Tab.
Sorry if this has been asked before but i couldn't see it.
I have tried to make an app that displays all the names of files on my SD card. Just at the top level. I made a quick interface with just a button and a text view to start (i'm away a single text view wont display a list but had problems but i got to that anyway)
ended up with the following code.
*public void ShowFolder(View view){
TextView test = (TextView)findViewById(R.id.View);
root = new File(Environment.getRootDirectory().toString());
File[] Files;
Files = root.listFiles();
String[] File_List;
File_List = root.list();*
I then ran this using the debugger to see what ended up in both the array lists.
I ran this code three times over but varied the "Environment.getRootDirectory" to "getExternalStorageDirectory()" and "getDataDirectory()".
Only the getRootDirectory version will return anything.In both other instances the debugger shows NULL for both Files and Files_list.
I know they are valid locations because used those commands then outputted to strings which i can manually find on my tablet with a file browser.
So, simply put, why dont all three of these options return file lists?
My first thought it permissions but I was unsure how to confirm this.
(Sorry for the long post)

Don't use toString() to create File. getRootDirectory() already returns File object.
Try something like this:
File root = Environment.getRootDirectory();
String[] rootList = root.list();
File[] rootListFiles = root.listFiles();
Also you need to obtain READ_EXTERNAL_STORAGE permission as you can see here in the docs of getExternalStorageDirectory()

C++ OpenCV imread not working in Android

I am trying to read an image in my C++ code
LOGD("Loading image '%s' ...\n", (*inFile).c_str());;
Mat img = imread(*inFile, CV_LOAD_IMAGE_GRAYSCALE);
CV_Assert(img.data != 0);
and get the following output:
09-25 17:08:24.798: D/IRISREC(12120): Loading image '/data/data/com.example.irisrec/files/input/osoba1.jpg' ...
09-25 17:08:24.798: E/cv::error()(12120): OpenCV Error: Assertion failed (img.data != 0) in int wahet_main(int, char**), file jni/wahet.cpp, line 4208
The file exists. But strange is, that if I try to preview the image using Root File Browser it is just black. I copied the files there manually.
EDIT:
The code works fine under Windows with .png and .jpg format. I am just trying to port an existing C++ project for Iris Recognition to Android.

imread() determines the type of file based on its content not by the file extension. If the header of the file is corrupted, it makes sense that the method fails.
Here are a few things you could try:
Copy those images back to the computer and see if they can be opened by other apps. There's a chance that they are corrupted in the device;
Make sure there is a file at that location and that your user has permission to read it;
Test with types of images (jpg, png, tiff, bmp, ...);
For testing purposes it's always better to be more direct. Get rid of inFile:
Example:
Mat img = imread("/data/data/com.example.irisrec/files/input/osoba1.jpg", CV_LOAD_IMAGE_GRAYSCALE);
if (!img.data) {
// Print error message and quit
}

When debugging, first try to get more data on the problem.
It's an unfortunate design that imread() doesn't provide any error info. The docs just say that it'll fail "because of missing file, improper permissions, unsupported or invalid format".
Use the debugger to step into the code if you can. Can you tell where it fails?
Search for known problems, stackoverflow.com/search?q=imread, e.g. imread not working in OpenCV.
Then generate as many hypotheses as you can. For each one, think of a way to test it. E.g.
The image file is malformed (as #karlphillip offered). -- See if other software can open the file.
The image file is not a supported format. -- Verify the file format on your desktop. Test that desktop OpenCV can read it. Check the docs to verify the image formats that AndroidCV can read.
The image file is not at the expected path. -- Write code to test if there's a file at that path, and verify its length.
The image file does not have read permission. -- Write code to open the file for reading.
A problem with the imread() arguments. -- Try defaulting the second argument.

I was able to solve this issue only by copying the image files in code.I stored them in my asset folder first and copied them to internal storage following this example.
If someone can explain this to me please do this.

It could be a permission issue.You would have to request the permission from Java code in your Activity class like this in Android 6.0 or above. Also make sure that in your AndroidManifest.xml, you have the the following line :
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
In your activity file add this:
if (PermissionUtils.requestPermission(
this,
HOME_SCREEN_ACTIVITY,
Manifest.permission.READ_EXTERNAL_STORAGE)) {
Mat image = Imgcodecs.imread(filePath,Imgcodecs.IMREAD_COLOR);
}
I struggled a long time to find this and I was getting Mat object null for all the time before.

Titanium 3.X getFile() from local storage

Using Titanium on Android 4+ I want to access a jpeg file which has been taken with the camera. I need to achieve 2 objectives, namely, return the EXIF data and transfer the bytes to an API endpoint. My problem is I'm unable to access the file...
I'm using a 3rd party module to handle the file selection (Multi Image Picker) which returns a list of file locations, using the File Manager app on the emulator (GenyMotion) I can confirm the location on disk is correct. However, the following always returns false...
var file = Ti.Filesystem.getFile('/mnt/sdcard/DCIM/Camera/IMG_20140901_083735.jpg');
Ti.API.info('Do we have a file? ' (file.exists()? 'YES' : 'NO'));
The output for the above would be... Do we have a file? NO
Further reading shows Titanium has 5 predefined folder locations which can be passed into the getFile() method and one possible reason for the above code not working would be it is defaulting to the 'Resouces' folder location? That said all but one folder location is app specific, the exception being externalStorageLocation. Now my understanding of an Android device is that any image taken with the camera will be stored on the internal storage system unless an SD card is present. This is true in my case as the following lists 0 files...
var extDir = Ti.Filesystem.getExternalStorageDirectory();
var dir = Ti.Filesystem.getFile(extDir);
var dir_files = dir.getDirectoryListing();
Ti.API.info('External files... ' + dir_files.length);
The output for the above would be... External files... 0
So am I right in thinking Appcelerator have simply not included the ability to access local storage (outside of any app specific folders) within their API? Or am I missing something and there is in fact another way?

Thanks to #Bharal I was able to find a solution...
By using the Ti.Media.openPhotoGallery() method I was able to identify the correct native path for the image by inspecting the event object returned from the success callback.
The path was missing 'file://' at the beginning, I couldn't be 100% sure but I suspect this forces the getFile() method to use an absolute path and not a relative path from within the Resources folder.
To confirm, the following will return a file object...
var file = Ti.Filesystem.getFile('file://[path]');
Where [path] is the folder location as reported within the File Manager app on the device, for example '/mnt/sdcard/DCIM/Camera/IMG_20140901_083735.jpg'

Yah mon, i dunno.
Here is wat i used when i was doin pictures on my Ti app, but then i got rid of that section because i realised i didn't need to be doin pictures. Pictures mon, dey ain' what you want sometimes, yo?
Ti.Media.openPhotoGallery({ //dissall jus' open up a piccha selectin' ting. ez.
success:function(event){
var image = event.media;
if (event.mediaType==Ti.Media.MEDIA_TYPE_PHOTO){
//so image.nativePath is the path to the image.
// profileImg be jus' some Ti.UI.createImageView ting yo be puttin in yo' page.
//meyybe yo be wantin' alert(image.nativePath); here too, dat be helpin?
profileImg.image = image.nativePath;
}
},
cancel:function(){
//we cancelled out, why we doin' that?
}
});
Now that isn't going to really be helpin' you, but yo can use that to see wat the native path yo piccha be usin' be, and then be seein' if maybe what yo be puttin' in yo code be sam ting.
Jus' wrap the above as an addEventListener("click", function(){ ... } ); on sam ting in yo page, and jus' add sam element to put th' piccha in if yo be wantin' to see the piccha but i be tellin' you picchas mon, sometimes dey ain' worth time.
But meyybe yo wantin' use not an emulator for dis ting, dey can be actin' weird yo should be usin some small phone maybe? Dat way you can be findin' if yo got dem memory leeks and meyybe some memory sprouts, an memory onions too.