I want to save files in local storage of Android/iOS. I followed the Flutter cookbook to save files but it didn't work. There are examples everywhere using the File class, but it's undefined when I use it. I'm using Dart 2.2.0 and Flutter 1.2.1
I've tried example code snippets from a few websites. Nothing worked. File class, readAsString, and writeAsString are undefined in my Dart file.
Here's the code. Checked it in DartPad. Where am I wrong?
//packages
import 'dart:io';
import 'dart:async';
import 'package:path_provider/path_provider.dart';
//start
class File {
/// Directory Path
/// Local Directory Path
Future<String> get _localPath async {
final directory = await getApplicationDocumentsDirectory();
// For your reference print the AppDoc directory
print(directory.path);
return directory.path;
}
/// Reference for file Location
Future<File> get _localFile async {
final path = await _localPath;
final address = '$path/data.txt';
return File(address);
}
/// Presenting different Data as 1 String
String convertingtoString(String title, String author, String content) {
return '$title\n$author\n\n$content';
}
/// Write to file
/// Writing as String
Future<File> writeContent(String matter) async {
/// Get matter converted to string as matter
final file = await _localFile;
// Write the file
return file.writeAsString(matter);
}
/// Read from file
Future<String> readcontent() async {
try {
final file = await _localFile;
// Read the file
String contents = await file.readAsString();
return contents;
} catch (e) {
// If there is an error reading, return a default String
return 'Error, Couldn\'t read file';
}
}
}
This is code from my android flutter project. I get the same errors like DartPad in VScode
You've created your own class named File, so that hides the File class from dart:io. Name your custom class something else, or do:
import 'dart:io' as io;
and use io.File where you intend to use dart:io's File class. (I recommend renaming your custom class to avoid confusion.)
Original answer
Since you have import 'dart:io';, the File class should be available to you.
If you're trying this solely with DartPad, then it (among other things) won't work there because dart:io is meant to be used with a Dart VM. dart:io won't work in a browser, which has a sandboxed environment and generally prevents filesystem access:
Important: Browser-based applications can't use this library. Only servers, command-line scripts, and Flutter mobile apps can import and use dart:io.
I wanted to know how I can get the absolute path of a file which is inside my project not in the application running.
For example this one:
C:\Users\Mr\Documents\Example\org.xtext.example.mydsl\src\example.txt
I have tried with paths like:
val file = new File("relative path");
val absolutePathString = file.getAbsolutePath();
or
System.getProperty("user.dir");
But all of them retrieves me Eclipse's path and not my project's path.
Thanks for the help!
There does not need to be a file. Assuming you have a default eclipse with default filesystem and talk about a file in a project you may have a look a at these
public void doit(Resource r) {
URI uri = r.getURI();
if (uri.isPlatformResource()) {
IFile file = ResourcesPlugin.getWorkspace().getRoot().getFile(new Path(uri.toPlatformString(true)));
file.getLocation();
file.getLocationURI();
file.getRawLocation();
file.getRawLocationURI();
}
}
I'm working on a Dart HttpServer using SSL, which looks something like this:
class Server {
//The path for the database is relative to the code's entry point (main.dart)
static const String CERTIFICATE_DB_PATH = '../lib/server/';
static const String CERTIFICATE_DB_PASS = '*******';
static const String CERTIFICATE_NAME = 'CN=mycert';
Future start() async {
SecureSocket.initialize(database: CERTIFICATE_DB_PATH, password: CERTIFICATE_DB_PASS);
httpServer = await HttpServer.bindSecure(ADDRESS, PORT, certificateName: CERTIFICATE_NAME);
listenSubscription = httpServer.listen(onRequest, onError: onError);
}
//more server code here
}
This all works exactly as expected, so no problems with the actual certificate or server code. The part that I'm having problems with is mentioned in that first comment. The CERTIFICATE_DB_PATH seems to be relative not to the file the Server class is defined in, but rather to the file that contains the main() method. This means that when I try to write a unit test for this class, the path is no longer pointing to the correct directory. If this were an import, I'd use the package:packageName/path/to/cert syntax, but it doesn't seem that applies here. How can I specify the path of the certificate in a way that will work with multiple entry points (actually running the server vs unit tests)?
I don't think there is a way to define the path so it is relative to the source file.
What you can do is to change the current working directory either before you run main() or pass a working directory path as argument to main() and let main() make this directory the current working directory.
Directory.current = someDirectory;
I'm writing a Jenkins plugin and i'm using build.getWorkspace() to get the path to the current workspace. The issue is that this returns a FilePath object.
How can i convert this to a File object?
Although I haven't tried this, according to the javadoc you can obtain the URI from which you can then create a file: File myFile = new File(build.getWorkspace().toURI())
Please use the act function and call your own FileCallable implementation if your plugin should work for master and slaves. For more information check the documentation, chapter "Using FilePath smartly" or this stackoverflow answer.
Code example (source):
void someMethod(FilePath file) {
// make 'file' a fresh empty directory.
file.act(new Freshen());
}
// if 'file' is on a different node, this FileCallable will
// be transferred to that node and executed there.
private static final class Freshen implements FileCallable<Void> {
private static final long serialVersionUID = 1;
#Override public Void invoke(File f, VirtualChannel channel) {
// f and file represent the same thing
f.deleteContents();
f.mkdirs();
return null;
}
}
This approach
File myFile = new File(build.getWorkspace().toURI()) is not the correct solution. I don't know why this has been an accepted anwser till date.
The approach mentioned by Sascha Vetter is correct, taking the reference from official Jenkins javadocs
,which clearly says and I quote
Unlike File, which always implies a file path on the current computer, FilePath represents a file path on a specific agent or the controller.
So being an active contributor to Jenkins community, I would reference the answer given by Sascha Vetter.
PS. Reputation point criteria makes me unable to up-vote the correct answer.
I would like to list all the contents of a directory (on the file system) using Dart. How can I do this?
How to list the contents of a directory in Dart
final dir = Directory('path/to/directory');
final List<FileSystemEntity> entities = await dir.list().toList();
This creates a Directory from a path. Then it converts it to a list of FileSystemEntity, which can be a File, a Directory, or a Link. By default subdirectories are not listed recursively.
If you want to print that list, then add this line:
entities.forEach(print);
If you want to only get the files then you could do it like so:
final Iterable<File> files = entities.whereType<File>();
The API has changed and I have updated the async code for M4 release (0.5.16_r23799 ):
Future<List<FileSystemEntity>> dirContents(Directory dir) {
var files = <FileSystemEntity>[];
var completer = Completer<List<FileSystemEntity>>();
var lister = dir.list(recursive: false);
lister.listen (
(file) => files.add(file),
// should also register onError
onDone: () => completer.complete(files)
);
return completer.future;
}
The list method returns a Stream where each emitted event is a directory entry:
Directory dir = Directory('.');
// execute an action on each entry
dir.list(recursive: false).forEach((f) {
print(f);
});
As the name suggest, listSync method is the blocking version:
// create a list of entries
List<FileSystemEntity> entries = dir.listSync(recursive: false).toList();
What method to use depends on application context. A note directly from the docs:
Unless you have a specific reason for using the synchronous version of a method, prefer the asynchronous version to avoid blocking your program.
This answer is out of date. Please see the accepted answer.
There are two ways to list the contents of a directory using the Dart VM and the dart:io library.
(note: the following only works in the Dart VM when running on the command-line or as a server-side app. This does not work in a browser or when compiled to JavaScript.)
Setup
First, you need to import the dart:io library. This library contains the classes required to access files, directories, and more.
import 'dart:io';
Second, create a new instance of the Directory class.
var dir = new Directory('path/to/my/dir');
Listing contents in a script
The easiest way is to use the new listSync method. This returns a List of contents. By default this does not recurse.
List contents = dir.listSync();
for (var fileOrDir in contents) {
if (fileOrDir is File) {
print(fileOrDir.name);
} else if (fileOrDir is Directory) {
print(fileOrDir.path);
}
}
If you want to recurse through directories, you can use the optional parameter recursive.
List allContents = dir.listSync(recursive: true);
WARNING if your directory structure has circular symlinks, the above code will crash because it's following symlinks recursively.
This method, using listSync, is especially useful when you are writing a shell script, command-line utility, or similar app or script with Dart.
Listing contents in a server
A second way to list the contents of a directory is to use the async version of list. You would use this second method when you need to list a directory in response to, say, an HTTP request. Remember that each of Dart's isolates runs in a single thread. Any long running process can block the event loop. When interactivity is important, or serving lots of clients from a single Dart script, use the async version.
With the async version, dir.list() returns a DirectoryLister. You can register three different callbacks on DirectoryLister:
onFile: called when a file or directory is encountered
onDone: called when the directory lister is done listing contents
onError: called when the lister encounters some error
Here is a simple function that returns a Future of a list of strings, containing file names in a directory:
Future<List<String>> dirContents(Directory dir) {
var filenames = <String>[];
var completer = new Completer();
var lister = dir.list();
lister.onFile = (filename) => filenames.add(filename);
// should also register onError
lister.onDone = (_) => completer.complete(filenames);
return completer.future;
}
Of course, this method is perfect for servers, it's more cumbersome for simple scripts.
Luckily, Dart supports both methods for you to use!
Inside and asynchronous function write this
List<FileSystemEntity> allContents = await Directory("folder/path").list().toList();
Now you have a list with all of the contents
Here is my version using async/await, returning a List of Files only:
List<File> filesInDirectory(Directory dir) async {
List<File> files = <File>[];
await for (FileSystemEntity entity in dir.list(recursive: false, followLinks: false)) {
FileSystemEntityType type = await FileSystemEntity.type(entity.path);
if (type == FileSystemEntityType.FILE) {
files.add(entity);
print(entity.path);
}
}
return files;
}
With this function you can print all the directories and files of a directory.
You just need to pass a specific path.
Future listDir(String folderPath) async {
var directory = new Directory(folderPath);
print(directory);
var exists = await directory.exists();
if (exists) {
print("exits");
directory
.list(recursive: true, followLinks: false)
.listen((FileSystemEntity entity) {
print(entity.path);
});
}
}
To get a list of file names with a certain string, you can use this code:
String directory = (await getApplicationDocumentsDirectory()).path;
List<FileSystemEntity> files = Directory(directory).listSync(recursive: false);
List<String> filePaths = [];
for (var fileSystemEntity in files) {
if (basename(fileSystemEntity.path).contains('mystring')) {
filePaths.add(fileSystemEntity.path);
}
}
You can use the basename function if you need just the file name, and not the whole path.
To get all files with given extension:
import 'package:path/path.dart' as p;
Future<List<File>> getAllFilesWithExtension(String path, String extension) async {
final List<FileSystemEntity> entities = await Directory(path).list().toList();
return entities.whereType<File>().where((element) => p.extension(element.path) == extension).toList();
}