i need to make a compiler in android using the jflex and cup tools to read a file in the internal storage of the movile.
but the user need to input the path of the file and the user input its like:
/home/cp21.txt
but when i use the method openFileInput() it reads
/data/data/com.aplicattionpakagename/files/cp21.txt
and the file is in the buetooh directory of "Almacenamiento de telefono"
how can i read it?
Try using something in external storage with getExternalStorageDirectory().
If you want the user interface to expose that as /home, make sure you do a String replace between your view and model, s.t. /home is converted to /path/to/storage, and vice versa.
Related
i'm currently trying to develop a package for a Flutter App, with Kotlin. My issue is that I need to provide the package with a config file, which should only be defined inside the main App. Since the config differs for the Dev and Prod environment, the app should pass through the path of the File via the Method Channel. The problem is that the package isn't able to access the assets folder of the calling application.
Path: "assets/config.json" (the root being the main application)
Steps I already tried:
Creating the file inside the res/raw & accessing the config file through a ressource id -> Kotlin gives me an "Unresolved reference" error, unless I create the file inside the packages res/raw
Instead of passing through the path, I tried passing through the content of the config & writing it into an empty temporary file. The code in Kotlin like this:
val config = File(applicationContext.filesDir,"config.json")
config.writeText(configContent)
-> This works, but it seems like a weird solution to the problem.
please let me know if I need to provide further information & thank you in advance!
edit:
The Java Method that is called during initialisation:
public static void createMultipleAccountPublicClientApplication(#NonNull final Context context,
#NonNull final File configFile,
#NonNull final IMultipleAccountApplicationCreatedListener listener)
Flutter assets aren't files - they are packaged up and only available through the rootBundle. So, if you want to make a file from a text asset, someone has to load the asset and write it to a file.
As your plugin user will be in charge of the asset, they will have to do the first part (and will end up with a String). The question arises of who should do the writing.
You could make the plugin user use path_provider to find the temporary directory and write it there and then pass you the file path. Eventually, down in the Java, you new File(theTempFilePath). Or they could pass the string to the Dart half of your plugin and you create the temp file in the same way.
It's probably more convenient if they pass your plugin the string, you pass that to the native side and have the native side create a temporary file and write the string there. (BTW, I assume we are talking about this config file: https://learn.microsoft.com/en-us/azure/active-directory/develop/msal-configuration#how-to-use-a-configuration-file )
See this answer for creating temporary files: Creating temporary files in Android
Note that there's actually no reason that your plugin user then needs to use an asset. They could, instead, just hard code the string in their code if the configuration never really changes.
There's an argument that as this is a JSON configuration file, you may not want to bother your user with the details of this JSON configuration file. You may want to default it in your Dart code (why not hard code it as a string, as above, if it never really changes) and then provide some methods to override particular values like the client id and the redirect uri, which may be the only things that users ever change in practice. So rather than making them supply a complete JSON file, they just give you those two strings and you plonk them into your default JSON. Maybe a version 2 feature :)
As Google is trying to enforcing apps to use SAF for storage access, I am trying to adapt my app to use SAF replacing java file io apis.
I have spent many hours study the SAF APIs (mainly DocumentFile and DocumentContract classes) but still have some difficulties.
First one is how to move a file to another directory? DocumentFile does have a method to rename a file, but it is just the display name of the file. How can I move a file to another folder, if it is a huge file which I don't want to copy it. Assume src and dst are on the same partition.
Second question is how to list child files efficiently. I checked the source code and found that DocumentFile.listFiles() impl only queries the child files with single projection [ID]. And later when I want to display the files in a list view with their names, the call to DocumentFile.getName() will trigger another query via content resolver for each file again. This is a huge impact on the performance of the code. Especially when I try to sort an array of DocumentFile by their names, 30+ files will cost 600+ms, which is far beyond the acceptable. I doubt whether I am using the correct API set. Could anyone point out a better way to list files with names (and other properties)?
Simple Storage is a library that simplify SAF across API levels. Suppose that you want to move a MP4 file from directory Video in external storage into directory Others in SD card. Let's assume that AAAA-BBBB as SD card's storage ID:
val source = DocumentFileCompat.fromSimplePath(context, basePath = "Video/Infinity War.mp4")
val targetFolder = DocumentFileCompat.fromSimplePath(context, storageId = "AAAA-BBBB", basePath = "Others")
// To move file:
source.moveFileTo(context, targetFolder, callback)
// To copy file:
source.copyFileTo(context, targetFolder, callback)
In C# there are Application.StartUpPath or Application.AppDataPath global methods to get a path where I would store Application Settings.
I tried static String fName = System.getProperty("user.dir") + "SatCli.conf";
"/SatCli.conf" - is the resulted fName
then I call
BufferedOutputStream oustream = new BufferedOutputStream(new
FileOutputStream(fName, false));
and I am getting the common exception
"/SatCli.conf: open failed: EROFS (Read-only file system)"
Well, I've been writing apps under Unix and I understand maybe the file name is refering to internal memory.. in other words to the root part of system file system.
Or maybe not.. maybe it refers to the App Folder?
Anyway, what I would like to get is the correct method to get the right folder to store the settings data.
Also, what is important, I need it before any context is built, when static fields are initializing.
Thank you for any relevant hint and help.
what I would like to get is the correct method to get the right folder to store the settings data.
For arbitrary files, call getFilesDir() on a Context (e.g., Activity). This gives you a File object representing a private directory where your app can read and write.
FWIW, Android's standard way of storing settings that you collect from the user is SharedPreferences, so you can take advantage of PreferenceFragment for the UI.
I need to read some data from file in internal storage, then remove and rewrite file with new data. What is the best way to do it(safest method for data)?
I'd first rename the original file (append something like .orig), then read it, write the new file and when all that's successful, remove the renamed original file. This ensures the most that no data gets lost.
In Reference to this android file download problem
Can anyone explain what does this line mean in the code
FileOutputStream f = new FileOutputStream(new File(root,"Video.mp4"));
And what does it mean by the parameter root within the File().
Do I need to specify the root path to save the file?
If it is the case then how do we specify the root path in android ?
Regards
And what does it mean by the parameter root within the File(). Do I need to specify the root path to save the file? if it is the case then how do we specify the root path in android?
The code snippet from the question you linked doesn't define the variable, but if the code is downloading a file to the device, I would assume that it's a path on the SD card. Environment.getExternalStorageDirectory() will give you the root path to the SD card. You'll also need to specify the WRITE_EXTERNAL_STORAGE permission in your manifest.
If you're working on the emulator, you can create a virtual SD card when you create the emulator image.
The java.io.File(File, String) or java.io.File(String, String) are standard java constructors for Java. The first argument is just the parent directory path, while the second is the actual file name. If the file is in the current working directory or you know the full path as one string you can avoid the 2 argument constructors.
Since you are trying to download a file you can just acquire the file through a normal URL.openStream() to get an InputStream to get the contents of your downloaded file. For writing the data out you will follow the example you linked to to write the contents.
I'm unsure what the root variable was pointed to in the example. I'm not able to help you beyond this though since I have only gone through the first Hello, Android example myself.