Develop Reference

Not able to open the file which is downloaded from the byte[] in xamarin.forms

I am trying to downlaod a file in a specified path in a device from the byte[]. I am able to see the documents in that path but not able to open them. When I try to open them it is showing the file can not be opend alert.
I am using the following code to download.
public async Task WriteBytesToFile(byte[] fileBytes, string fileFullPath)
{
string pathToNewFolder = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.AbsolutePath, "Test");
Directory.CreateDirectory(pathToNewFolder);
File.WriteAllBytes(fileFullPath,fileBytes);
}

Getting a file extension from dropbox or driver after onActivityResult()

I use this code for upload file:
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (resultCode == RESULT_OK) {
final String path = getPath(data.getData());
final String fileExt = path.substring(path.lastIndexOf(".") + 1);
}
}
This code work fine for select file from SDCard. But if I select file from Drive or Dropbox on line 4 I get error.
Anyone knows why it happens like that.

This code work fine for select file from SDCard.
Not necessarily. After all, files do not have to have extensions. README is a valid filename, and it does not have a file extension.
But if I select file from Drive or Dropbox on line 4 I get error
Sure. There is no requirement for a Uri to have a file extension. For example, https://stackoverflow.com/questions/53131985/android-get-extension-file-from-dropbox-or-driver-after-onactivityresult is a Uri, and it does not have a file extension.
If data.getData().getScheme() returns file, you are welcome to try your algorithm, but it will fail for README.
If data.getData().getScheme() returns content, you can use getContentResolver().getType(data.getData()) to get a MIME type for the content. You can then try to use MimeTypeMap to identify a file extension, though MimeTypeMap does not handle all possible MIME types.
Overall, you need to revise your plans, such that you do not need file extensions.

Trouble loading local html file into default device browser in Android app

I am an iOS developer assigned a task in Android, so bear with me, I'm a bit green in Android.
I am attempting to load a local html file that is stored in the device download directory in a folder called user_guide. I want the html file to load in the device's browser (not in a webview for reasons outside the scope of this post). I am using the following code to launch the browser:
String downloadPath = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).toString();
String path = "file://" + downloadPath + "/user_guide/index.html"; // + R.raw.test;
Uri pathUrl = Uri.parse(path);
Intent browserIntent = new Intent(Intent.ACTION_VIEW);
browserIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
browserIntent.setData(pathUrl);
context.startActivity(browserIntent);
I obtained the value of path by setting a breakpoint and manually set it in Chrome on my device to verify that is does work and loads the proper file. However, when I try to run this code in the app, I get the following toast message:
Cannot display PDF (index.html is of invalid format)
I'm confused about this message since I am trying to load an html file, not a PDF. Can anyone help me out? THanks!

Try changing "browserIntent.setData(pathUrl)" to
browserIntent.setDataAndType(pathUrl, "text/html")
to explicitly specify that it's HTML.
I found this suggestion at https://stackoverflow.com/a/7009685/10300291.

How to pick file from external storage using file picker in Android

I am having a problem with selecting image file from external storage using file picker in Android. This question is the consequence of this question - No such file or diectory error in image file upload using Retrofit in Android. What my problem is opening and reading file from external storage on activity result. I want to convert result URI into File.
I read a pdf file from download folder on activity result
Uri bookUri = data.getData();
if(bookUri!=null)
{
String filePath = bookUri.toString();//bookUri.toString()
String mime = app.getMimeType(filePath);
if(mime!=null && !mime.isEmpty() && (mime.toLowerCase()=="application/pdf" || mime.toLowerCase()=="application/txt" || mime.toLowerCase()=="application/text"))
{
bookFile = new File(bookUri.getPath());
ivBookFile.setImageResource(R.drawable.book_selected);
}
else{
Toast.makeText(getBaseContext(),"Unable to process file you have chosen.",Toast.LENGTH_SHORT).show();
}
}
As you can see I used new File(bookUri.getPath()); to convert into File. The above code works well. It is working. The problem is now I am trying to open an image file in DCIM/Camera folder on activity result.
This is the code I used
Uri selectedImageUri = data.getData();
if(selectedImageUri!=null)
{
try{
bmpCoverImage = MediaStore.Images.Media.getBitmap(getContentResolver(), selectedImageUri);
imageFile = new File(selectedImageUri.getPath());
if(bmpCoverImage!=null)
{
ivCoverImage.setImageBitmap(bmpCoverImage);
}
}
catch (IOException e)
{
Toast.makeText(getBaseContext(),"An error occurred with the file selected",Toast.LENGTH_SHORT).show();
}
}
As you can see I used new File(selectedImageUri.getPath()); like I did in reading pdf file. This time the code is not working. When I do operation with the file like in previous question, it gives me error.
I used this way also
imageFile = new File(Environment.getExternalStorageDirectory(),selectedImageUri.getPath());
I got the same error. How can I open the image file correctly from external storage? How can I convert the chosen file URI from external storage into File?

I am having a problem with selecting image file from external storage using file picker in Android
If you are referring to the code that you are using in this question, you are not "using file picker". You are using ACTION_GET_CONTENT, which has never been a "file picker", nor will it ever be a "file picker".
I want to convert result URI into File.
Usually, that is not necessary. But, if that is what you want to do:
use ContentResolver and openInputStream() to get an InputStream on the content represented by the Uri
create a FileOutputStream on your desired file
use Java I/O to copy the bytes from the InputStream into the FileOutputStream
The above code works well. It is working.
It works for the small number of devices that you tested, for the specific activities that the user chose to handle the ACTION_GET_CONTENT request. It will not work on most Android devices, and it will not work in most circumstances. The only time that code will work is if the Uri has a file scheme. Most of the time, it will not. Instead, it will have a content scheme, representing content supplied by a ContentProvider.
Please how can I open the image file correctly from external storage?
If you wish to continue using ACTION_GET_CONTENT, please understand that this has nothing to do with external storage specifically. You are not getting a file, on external storage or elsewhere. You are getting a Uri. This is akin to a URL, such as the URL for this Web page. Just as a URL does not necessarily point to a file on your hard drive, a Uri does not necessarily point to a file on the filesystem. Use a ContentResolver and DocumentFile to work with the Uri and the content that it identifies.
If you want to always get files on external storage (and nowhere else), then use an actual file picker library.

Android: Content type error using ACTION_VIEW with a local file

I'm trying to post a notification that lets the user open a locally stored file. My code looks like this:
Intent notificationIntent = new Intent(Intent.ACTION_VIEW);
notificationIntent.setAction(android.content.Intent.ACTION_VIEW);
Uri uri = Uri.fromFile(new File(filename));
notificationIntent.setData(uri);
Where "filename" is the full path to a locally stored file, usually in the /mnt/sdcard/download directory. The files I want to display are of various types: images, PDF documents, HTML, etc.
This works, but sometimes Android tries to open the file as the wrong type. For example, a jpeg file will open in a web browser view and instead of seeing the image, I see the binary data from the file displayed as text. Other times it works file. For example, some PDF files correctly open in a PDF viewer and some do not.
I'm not sure why this is. The documentation says I should not have to pass an explicit content type. If I do set the content type explicitly, things seem to work fine. The problem is, I don't always know what the content type should be (the file is downloaded from an external source and can be anything, and no, the MIME type is not in the HTTP headers, I checked for that).
What can I do here? Is there some function I can call with a filename to have Android return me the best content type for that file? Moreover, why is this not happening automatically when the Intent is processed?
Thanks.

You've most likely figured this out; I'm posting in case someone else is stuck on this. I do the following to get the mime-type of the file:
//Get the file path
Uri path = Uri.fromFile(file);
MimeTypeMap type_map = MimeTypeMap.getSingleton();
//Get the extension from the path
String extension = MimeTypeMap.getFileExtensionFromUrl(path.toString());
extension = extension.toLowerCase();
if (extension.contains(".")) {
extension = extension.substring(extension.lastIndexOf("."));
}
String mime_type = type_map.getMimeTypeFromExtension(extension);