fetch 方法
实现
Future<BackgroundFetchRegistration> fetch(String id, Object requests,
[Map? options]) {
var options_dict = null;
if (options != null) {
options_dict = convertDartToNative_Dictionary(options);
}
return promiseToFuture<BackgroundFetchRegistration>(JS(
"creates:BackgroundFetchRegistration;",
"#.fetch(#, #, #)",
this,
id,
requests,
options_dict));
}