我想在构建小部件后经过一定的延迟后执行一个函数。在 Flutter 中执行此操作的惯用方法是什么?
我想要实现的目标: 我想从默认的
FlutterLogo
小部件开始,然后在一段时间后更改其 style
属性。
Future.delayed
一段时间后运行您的代码。例如:
Future.delayed(const Duration(milliseconds: 500), () {
// Here you can write your code
setState(() {
// Here you can write your code for open new view
});
});
在setState函数中,您可以编写与应用程序UI相关的代码,例如刷新屏幕数据、更改标签文本等
使用
Timer
,定时器类文档
import 'dart:async';
倒计时后触发动作
Timer(Duration(seconds: 3), () {
print("Yeah, this line is printed after 3 seconds");
});
重复动作
Timer.periodic(Duration(seconds: 5), (timer) {
print(DateTime.now());
});
立即触发定时器
Timer(Duration(seconds: 0), () {
print("Yeah, this line is printed immediately");
});
留下大家都在寻找的片段:
Future.delayed(Duration(milliseconds: 100), () {
// Do something
});
想通了😎
class AnimatedFlutterLogo extends StatefulWidget {
@override
State<StatefulWidget> createState() => new _AnimatedFlutterLogoState();
}
class _AnimatedFlutterLogoState extends State<AnimatedFlutterLogo> {
Timer _timer;
FlutterLogoStyle _logoStyle = FlutterLogoStyle.markOnly;
_AnimatedFlutterLogoState() {
_timer = new Timer(const Duration(milliseconds: 400), () {
setState(() {
_logoStyle = FlutterLogoStyle.horizontal;
});
});
}
@override
void dispose() {
super.dispose();
_timer.cancel();
}
@override
Widget build(BuildContext context) {
return new FlutterLogo(
size: 200.0,
textColor: Palette.white,
style: _logoStyle,
);
}
}
(添加对旧 q 的响应,因为这是谷歌上的最佳结果)
我尝试在块内的回调中产生一个新状态,但它不起作用。尝试使用 Timer 和 Future.delayed。
但是,有效的是......
await Future.delayed(const Duration(milliseconds: 500));
yield newState;
等待一个空的 future,然后运行该函数。
Synchronously
Future.delayed(Duration(milliseconds: 1000), () {
// Your code
});
Asynchronously
await Future.delayed(const Duration(milliseconds: 1000));
一种快速的方法是使用
Future.delayed
,如下所示:
Future.delayed(Duration(seconds: 10), (){
print("Wait for 10 seconds");
});
或者您可以将持续时间更改为
milliseconds
,如下所示:
Future.delayed(Duration(milliseconds: 3000), () {
print("Wait for 3000 milliseconds");
});
Future.delayed(Duration(seconds: 3) , your_function)
只是在上述答案的基础上添加更多描述
计时器功能也适用于以下持续时间:
const Duration(
{int days = 0,
int hours = 0,
int minutes = 0,
int seconds = 0,
int milliseconds = 0,
int microseconds = 0})
示例:
Timer(Duration(seconds: 3), () {
print("print after every 3 seconds");
});
import 'dart:async';
Timer timer;
void autoPress(){
timer = new Timer(const Duration(seconds:2),(){
print("This line will print after two seconds");
});
}
autoPress();