How to download a file on flutter? - flutter

Question

How to download a .pdf file from an URL with POST Request having headers in Flutter?
i have a different pdf files for each user and i want the link to be different depend on the user.

Answer 1

You can use flutter_downloader plugin for downloading your files.
dependencies:
flutter_downloader: ^1.8.4
And also you can use this codebase for that:
import 'dart:io';
import 'dart:ui';
import 'package:fimber/fimber.dart';
import 'package:flutter_downloader/flutter_downloader.dart';
import 'package:path_provider/path_provider.dart';
import 'package:permission_handler/permission_handler.dart';
class DownloadingService {
static const downloadingPortName = 'downloading';
static Future<void> createDownloadTask(String url) async {
final _storagePermission = await _permissionGranted();
Fimber.d('Current storage permission: $_storagePermission');
if (!_storagePermission) {
final _status = await Permission.storage.request();
if (!_status.isGranted) {
Fimber.d('Permission wasnt granted. Cancelling downloading');
return;
}
}
final _path = await _getPath();
Fimber.d('Downloading path $_path');
if (_path == null) {
Fimber.d('Got empty path. Cannot start downloading');
return;
}
final taskId = await FlutterDownloader.enqueue(
url: url,
savedDir: _path,
showNotification: true,
// show download progress in status bar (for Android)
openFileFromNotification: true,
// click on notification to open downloaded file (for Android)
saveInPublicStorage: true);
await Future.delayed(const Duration(seconds: 1));
if (taskId != null) {
await FlutterDownloader.open(taskId: taskId);
}
}
static Future<bool> _permissionGranted() async {
return await Permission.storage.isGranted;
}
static Future<String?> _getPath() async {
if (Platform.isAndroid) {
final _externalDir = await getExternalStorageDirectory();
return _externalDir?.path;
}
return (await getApplicationDocumentsDirectory()).absolute.path;
}
static downloadingCallBack(id, status, progress) {
final _sendPort = IsolateNameServer.lookupPortByName(downloadingPortName);
if (_sendPort != null) {
_sendPort.send([id, status, progress]);
} else {
Fimber.e('SendPort is null. Cannot find isolate $downloadingPortName');
}
}
}
And in another page you can use this class to download your file:
final _receivePort = ReceivePort();
#override
void initState() {
super.initState();
IsolateNameServer.registerPortWithName(
_receivePort.sendPort, DownloadingService.downloadingPortName);
FlutterDownloader.registerCallback(DownloadingService.downloadingCallBack);
_receivePort.listen((message) {
Fimber.d('Got message from port: $message');
});
}
#override
void dispose() {
_receivePort.close();
super.dispose();
}
void _downloadFile() async {
try {
await DownloadingService.createDownloadTask(url.toString());
} catch (e) {
print("error")
}
}