How to show picked image with file_picker in web? - flutter

Question

how can I show image picked by file_picker in web while the file path is null in web platform ?
If the path was not null, showing the image is too easy with Image.file(File):
Image.file(context.select<BlogProvider, File>((BlogProvider p) => p.image))
but It can not create File for image in web because browsers don't give file path and It's null.
Future<void> pickImage() async {
/// If [withReadStream] is set, picked files will have its byte data available as a [Stream<List<int>>]
/// which can be useful for uploading and processing large files.
FilePickerResult result = await FilePicker.platform.pickFiles(
type: FileType.custom,
allowedExtensions: ['jpg', 'jpeg'],
withReadStream: true,
);
if (result != null) {
PlatformFile file = result.files.single; //single means I am Picking just One file not more
_blogImage = File(file.path);//Null in web ,but Ok in Android
notifyListeners();
} else {
// User canceled the picker
}
}

Answer 1

When withReadStream is set to true, selected image can be accessed as:
file.readStream.listen((event) {
_blogImage = Image.memory(event);
notifyListeners();
});
but when withReadStream is false:
_blogImage = Image.memory(file.bytes);
notifyListeners();
And although file.path is null in flutter for web, the file.name is set correctly and we can display it.
More info here
Another way (without file_picker package):
import 'dart:html' as html;
// ...
void pickFile() {
final input = html.FileUploadInputElement()..accept = 'image/*';
input.onChange.listen((event) {
if (input.files.isNotEmpty) {
fileName = input.files.first.name; // file name without path!
// synthetic file path can be used with Image.network()
url = html.Url.createObjectUrl(input.files.first);
});
}
});
input.click();
}

Answer 2

You can use Image.memory()
an exemple using the package universal_html
void main() {
runApp(
MaterialApp(
home: Scaffold(
body: DemoApp0(),
),
),
);
}
class DemoApp0 extends StatefulWidget {
DemoApp0({
Key key,
}) : super(key: key);
#override
_DemoApp0State createState() => _DemoApp0State();
}
class _DemoApp0State extends State<DemoApp0> {
final Map<String, Uint8List> files = {};
#override
Widget build(BuildContext context) {
return Center(
child: Column(
children: [
TextButton(
onPressed: ()=>pickWebFile(),
child: Text("select file"),
),
Column(
children: files.entries
.map((e) => Column(
children: [
Text(e.key),
SizedBox(
width: 200,
height: 300,
child: Image.memory(e.value),
)
],
))
.toList(),
)
],
),
);
}
Future<void> pickWebFile() async {
List<html.File> webFiles = [];
html.InputElement uploadInput = html.FileUploadInputElement();
uploadInput.click();
uploadInput.onChange.listen((e) {
webFiles = uploadInput.files;
for (html.File webFile in webFiles) {
var r = new html.FileReader();
Uint8List fileData;
r.readAsArrayBuffer(webFile);
r.onLoadEnd.listen((e) async {
fileData = r.result;
if (webFile.size < 4194304) {
setState(() {
files[webFile.name] = fileData;
});
}
});
}
});
}
}