Opening a newly created File in Dart - file

Question

I am new to dart and am currently trying to create a file from a data String.
All looks good so far as the length is not 0. But when i open the file, it instantly closes again, no console output, no errors.
I'd appreciate any pointers in the right direction, if any information is missing, please point it out and i will provide if possible.
void createFile(data) async{
Directory tempDir = await getTemporaryDirectory();
String tempPath = tempDir.path;
var file = new File(tempPath+widget.tileText);
var sink = file.openWrite();
sink.write(data.codeUnits);
await sink.flush();
await sink.close();
print(await file.length());
OpenFile.open(file.path);
}
UPDATE: added flush() and await before close() - loading a little smoother now, but File still closes instantly
Update2: removed create() (was a misunderstanding on my part)
now getting console output when the File closes: D/EGL_emulation(23235): eglCreateContext: 0xef02d650: maj 2 min 0 rcv 2
Running i ton my phone gives no console log, instead a simple "Can't open File" from the viewing application,i doublechecked the Path, it looks ok and it exists

Answer 1

So i found 2 problems and solved it now:
The path was missing a "/"
I didn't format the data right, i had to decode it and use writeAsBytes(), ditched the sink
now it's working
void createFile(data) async{
Directory tempDir = await getTemporaryDirectory();
String tempPath = tempDir.path;
var file = new File(tempPath+"/"+widget.tileText);
await file.writeAsBytes(base64Decode(data));
print(await file.length());
OpenFile.open(file.path);
print(await tempDir.exists());
print(file.path);
}