upload method
Implementation
Future<String?> upload(File file, String path,
{bool? overwrite, void onProgressUpdate(int progress)?}) {
Map<String, dynamic> args = <String, dynamic>{
"filePath": file.path,
"path": path,
"overwrite": overwrite
};
if (onProgressUpdate != null) {
int handle = _nextUploadHandle++;
UploadCallback uploadCallback = new UploadCallback(onProgressUpdate);
_uploadCallbacks[handle] = uploadCallback;
args["handle"] = handle;
}
return _channel.invokeMethod("Backendless.Files.upload", args);
}