public static Future <R> compute <Q, R>(ComputeCallback <Q, R> callback, Q message, string debugLabel = null)
{
var completer = Completer.create();
var isolate = Isolate.current;
var backgroundWorker = new BackgroundWorker();
backgroundWorker.DoWork += (sender, args) => { args.Result = callback((Q)args.Argument); };
backgroundWorker.RunWorkerCompleted += (o, a) => {
if (!isolate.isValid)
{
return;
}
using (Isolate.getScope(isolate)) {
if (a.Error != null)
{
completer.completeError(a.Error);
}
else
{
completer.complete(FutureOr.value((R)a.Result));
}
}
};
backgroundWorker.RunWorkerAsync(message);
return(completer.future.to <R>());
}
public override Future <byte[]> load(string key)
{
var completer = Completer.create();
var isolate = Isolate.current;
var panel = UIWidgetsPanelWrapper.current.window;
if (panel.isActive())
{
panel.startCoroutine(_loadCoroutine(key, completer, isolate));
}
return(completer.future.to <byte[]>());
}
void _show()
{
D.assert(_mode != _RefreshIndicatorMode.refresh);
D.assert(_mode != _RefreshIndicatorMode.snap);
Completer completer = Completer.create();
_pendingRefreshFuture = completer.future;
_mode = _RefreshIndicatorMode.snap;
_positionController
.animateTo(1.0f / RefreshIndicatorUtils._kDragSizeFactorLimit,
duration: RefreshIndicatorUtils._kIndicatorSnapDuration)
.then((value) => {
if (mounted && _mode == _RefreshIndicatorMode.snap)
{
D.assert(widget.onRefresh != null);
setState(() => { _mode = _RefreshIndicatorMode.refresh; });
Future refreshResult = widget.onRefresh();
D.assert(() => {
if (refreshResult == null)
{
UIWidgetsError.reportError(new UIWidgetsErrorDetails(
exception: new UIWidgetsError(
"The onRefresh callback returned null.\n" +
"The RefreshIndicator onRefresh callback must return a Promise."
),
context: new ErrorDescription("when calling onRefresh"),
library: "material library"
));
}
return(true);
});
if (refreshResult == null)
{
return;
}
refreshResult.whenComplete(() => {
if (mounted && _mode == _RefreshIndicatorMode.refresh)
{
completer.complete();
_dismiss(_RefreshIndicatorMode.done);
}
});
}
});
}
private Future _handleRefresh()
{
Completer completer = Completer.create();
Timer.create(new TimeSpan(0, 0, 0, 3), () => { completer.complete(); });
return(completer.future.then((_) =>
{
_scaffoldKey.currentState?.showSnackBar(new SnackBar(
content: new Text("Refresh complete"),
action: new SnackBarAction(
label: "RETRY",
onPressed: () => { _refreshIndicatorKey.currentState.show(); }
)
));
}));
}
Future <byte[]> _sendPlatformMessage(string channel, byte[] message)
{
Completer completer = Completer.create();
Window.instance.sendPlatformMessage(channel, message, (reply) => {
try {
completer.complete(FutureOr.value(reply));
}
catch (Exception exception) {
UIWidgetsError.reportError(new UIWidgetsErrorDetails(
exception: exception,
library: "services library",
context: new ErrorDescription("during a platform message response callback")
));
}
});
return(completer.future.to <byte[]>());
}
Future <Codec> _loadAsync(NetworkImage key, DecoderCallback decode)
{
var completer = Completer.create();
var isolate = Isolate.current;
var panel = UIWidgetsPanelWrapper.current.window;
if (panel.isActive())
{
panel.startCoroutine(_loadCoroutine(key.url, completer, isolate));
return(completer.future.to <byte[]>().then_ <byte[]>(data => {
if (data != null && data.Length > 0)
{
return decode(data);
}
throw new Exception("not loaded");
}).to <Codec>());
}
return(new Future <Codec>(Future.create(() => FutureOr.value(null))));
}
public override Future <T> loadStructuredData <T>(string key, Func <string, Future <T> > parser)
{
D.assert(key != null);
D.assert(parser != null);
if (_structuredDataCache.ContainsKey(key))
{
return(_structuredDataCache[key].to <T>());
}
Completer completer = null;
Future <T> result = null;
loadString(key, cache: false).then_ <T>(value => parser(value)).then_ <object>((T value) => {
result = new SynchronousFuture <T>(value);
_structuredDataCache[key] = result;
if (completer != null)
{
// We already returned from the loadStructuredData function, which means
// we are in the asynchronous mode. Pass the value to the completer. The
// completer's future is what we returned.
completer.complete(FutureOr.value(value));
}
return(FutureOr.nil);
});
if (result != null)
{
// The code above ran synchronously, and came up with an answer.
// Return the SynchronousFuture that we created above.
return(result);
}
// The code above hasn't yet run its "then" handler yet. Let's prepare a
// completer for it to use when it does run.
completer = Completer.create();
_structuredDataCache[key] = result = completer.future.to <T>();
return(result);
}
public static Future precacheImage(
ImageProvider provider,
BuildContext context,
Size size = null,
ImageErrorListener onError = null
)
{
var config = createLocalImageConfiguration(context: context, size: size);
var completer = Completer.create();
var stream = provider.resolve(configuration: config);
ImageStreamListener listener = null;
listener = new ImageStreamListener(
(image, sync) => {
if (!completer.isCompleted)
{
completer.complete();
}
SchedulerBinding.instance.addPostFrameCallback(timeStamp => {
stream.removeListener(listener: listener);
});
},
onError: error => {
if (!completer.isCompleted)
{
completer.complete();
}
stream.removeListener(listener: listener);
UIWidgetsError.reportError(new UIWidgetsErrorDetails(
context: new ErrorDescription("image failed to precache"),
library: "image resource service",
silent: true));
}
);
stream.addListener(listener: listener);
return(completer.future);
}
public DrivenScrollActivity(
ScrollActivityDelegate del,
float from,
float to,
TimeSpan duration,
Curve curve,
TickerProvider vsync
) : base(del)
{
D.assert(duration > TimeSpan.Zero);
D.assert(curve != null);
_completer = Completer.create();
_controller = AnimationController.unbounded(
value: from,
debugLabel: GetType().ToString(),
vsync: vsync
);
_controller.addListener(_tick);
_controller.animateTo(to, duration: duration, curve: curve)
.then(o => _end());
}
public override Future <_SizeAwareCacheKey> obtainKey(ImageConfiguration configuration)
{
Completer completer = null;
SynchronousFuture <_SizeAwareCacheKey> result = null;
imageProvider.obtainKey(configuration).then((object key) => {
// TODO: completer is always null?
if (completer == null)
{
result = new SynchronousFuture <_SizeAwareCacheKey>(new _SizeAwareCacheKey(key, width, height));
}
else
{
completer.complete(FutureOr.value(new _SizeAwareCacheKey(key, width, height)));
}
});
if (result != null)
{
return(result);
}
completer = Completer.create();
return(completer.future.to <_SizeAwareCacheKey>());
}
public override Widget build(BuildContext context)
{
Future <byte[]> f = null;
var completer = Completer.create();
var isolate = Isolate.current;
var panel = UIWidgetsPanelWrapper.current.window;
if (panel.isActive())
{
panel.startCoroutine(_loadCoroutine("https://buljan.rcsdk8.org/sites/main/files/main-images/camera_lense_0.jpeg", completer, isolate));
f = completer.future.to <byte[]>().then_ <byte[]>(data => {
if (data != null && data.Length > 0)
{
return(data);
}
throw new Exception("not loaded");
});
}
var futureBuilder = new FutureBuilder <byte[]>(
future: f,
builder: (ctx, snapshot) =>
{
int width = 200;
int height = 200;
Color color = Colors.blue;
if (snapshot.connectionState == ConnectionState.done)
{
return(new Container(alignment: Alignment.center, width: width, height: height, color: color, child: Image.memory(snapshot.data)));
}
else if (snapshot.connectionState == ConnectionState.waiting)
{
return(new Container(alignment: Alignment.center, width: width, height: height, color: color, child: new Text("waiting")));
}
else
{
return(new Container(alignment: Alignment.center, width: width, height: height, color: color, child: new Text("else")));
}
}
);
var streamBuilder = new StreamBuilder <int>(
stream: myStream,
initialData: 1,
builder: (ctx, snapshot) =>
{
var data = snapshot.data;
return(new Container(child: new Text($"stream data: {data}")));
}
);
return(new Container(
color: Colors.blueGrey,
child: new Column(
children: new List <Widget>
{
streamBuilder,
futureBuilder
}
)
));
}
// @override
// Stream<T> asStream() {
// final StreamController<T> controller = StreamController<T>();
// controller.add(_value);
// controller.close();
// return controller.stream;
// }
public override Future catchError(Func <Exception, FutureOr> onError, Func <Exception, bool> test = null)
{
return(Completer.create().future);
}