dart-async

问题 Background - want to utilise a dynamic list of items for a StatefulWidget. In my usecase the widget will be calling a CustomePainter (canvas) so sometimes there will be a varying number of images to be drawn on the canvas, hence within parent StatefulWidget would like to have an "array of images". Question - if using an array as the state variable what do I need to do programmtically (if anything) to ensure only the items that have changed within the array do infact get "redrawn", in

问题 I have some basic code to load some sprite images, I am using Future.wait to wait until both images are loaded. However this still does not what I exactly want to do, Because I want to assign image width and height to members before It exits. SpaceShip(this.x, this.y) { rocket = new ImageElement(src: "nofire.png"); firingRockets = new ImageElement(src: "fire.png"); var futures = [rocket.onLoad.first, firingRockets.onLoad.first]; Future.wait(futures).then((_) { width = rocket.width; height =

问题 I have some basic code to load some sprite images, I am using Future.wait to wait until both images are loaded. However this still does not what I exactly want to do, Because I want to assign image width and height to members before It exits. SpaceShip(this.x, this.y) { rocket = new ImageElement(src: "nofire.png"); firingRockets = new ImageElement(src: "fire.png"); var futures = [rocket.onLoad.first, firingRockets.onLoad.first]; Future.wait(futures).then((_) { width = rocket.width; height =

问题 I have some basic code to load some sprite images, I am using Future.wait to wait until both images are loaded. However this still does not what I exactly want to do, Because I want to assign image width and height to members before It exits. SpaceShip(this.x, this.y) { rocket = new ImageElement(src: "nofire.png"); firingRockets = new ImageElement(src: "fire.png"); var futures = [rocket.onLoad.first, firingRockets.onLoad.first]; Future.wait(futures).then((_) { width = rocket.width; height =

问题 How would one load a set of local images for display in a widget (noting this is async - see function below) triggered by (based on) a change in state from a flutter_bloc for “settings”? Noting this bloc is persisted too via hydrated_bloc. So the use case for which I’m asking how do I code this in flutter (noting I’m using flutter_bloc) is: Use Case - Render different set of images on the same Widget I have for dynamically displaying a room for a 2D point & click adventure type game, BASED ON

问题 I'm trying create a function to load images in Flutter (Dart) but not sure how to get this code working. I'm getting: A value of type 'Future' can't be assigned to a variable of type 'Image'. Try changing the type of the variable, or casting the right-hand type to 'Image'. import 'dart:typed_data'; import 'dart:ui' as ui; import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; void main() { runApp(MyApp()); } class MyApp extends StatelessWidget { @override Widget build

问题 i am trying to understand, how dart event loop works. I read the event loop article from the website The Event Loop and Dart and the author explain pretty good how event loop in dart works. But what i don't understand is, how event get queue. For example new Future(() => 21) .then((v) => v*2) .then((v) => print(v)); Will here dart gonna create three entries in the event queue or just one? I know, that the class Future is responsible for delay execution and when i create an object from it like

问题 If some code returns a future and determines that the future should return "Error" or "Exception" how can a stack trace be passed to Completer.completeException(exception, stackTrace); 回答1: If I understand correctly: when you catch an exception in dart, you can also catch the stack trace: try { // something } catch(e, stacktrace) { myCompleter.completeException(e, stacktrace); } 回答2: If you're not in a catch block, you can use StackTrace.current 来源： https://stackoverflow.com/questions

问题 Basically I am trying to make an app whose content will be updated with an async function that takes information from a website, but when I do try to set the new state, it doesn't reload the new content. If I debug the app, it shows that the current content is the new one, but after "rebuilding" the whole widget, it doesn't show the new info. Edit: loadData ( ) method, basically read a URL with http package, the URL contains a JSON file whose content changes every 5 minutes with new news. For

问题 Basically I am trying to make an app whose content will be updated with an async function that takes information from a website, but when I do try to set the new state, it doesn't reload the new content. If I debug the app, it shows that the current content is the new one, but after "rebuilding" the whole widget, it doesn't show the new info. Edit: loadData ( ) method, basically read a URL with http package, the URL contains a JSON file whose content changes every 5 minutes with new news. For