Flutter Future异步操作详细讲解

import 'dart:match';
import 'dart:async';
int getInt(){
print('执行getInt的函数');
Random rng = Random();
return rng.nextInt(100);
}
void main(){
//此处调用的getint函数是int类型
Future<int> future = Future(getInt);
//验证是否Future<int>的实例
print(Future(getInt));
}

import 'dart:match';
import 'dart:async';
int getInt() async{
print('执行getInt的函数');
Random rng = Random();
return rng.nextInt(100);
}
void main(){
//此处调用的getint函数是int类型
Future<int> future = Future(getInt);
//验证是否Future<int>的实例
print(Future(getInt));
}

import 'dart:match';
import 'dart:async';
int getInt(){
print('执行getInt的函数');
Random rng = Random();
return rng.nextInt(100);
}
void main(){
//此处调用的getint函数是int类型
Future<int> future = Future(getInt);
future.then((Object onValue){
print('异步调用成功,值为$onValue');
}).catchError((Object onError){
print('异步调用失败,值为$onError');
}).whenCompete((){
print('异步操作完成');
});
}

import 'dart:match';
import 'dart:async';
int getInt(){
print('执行getInt的函数');
Random rng = Random();
return rng.nextInt(100);
}
void main() async{
//此处调用的getint函数是int类型
Future<int> future = Future(getInt);
try{
//使用await等待异步调用完成使其等同意同步代码
	var onvalue = await getInt();
	print('一步操作成功：$onvalue');
}on Excrption catch(onError){
	print('异步捕获失败：$onError');
}finally{
	print('异步捕获完成');
}
}

//创建Stream
StreamController<int> controller = StreamController<int>(
	onListen: startTimer,
	onPause: stopTimer,
	onResume: startTimer,
	onCAncel: stoptimer
);
Stream stream = controller.stream;

import 'dart:async';
Stream<int> createStream(Duration interval,int maxCount){
	//定义流控制器
	StreamController<int> controller;
	 //定义定时器
	Timer timer;
	//计数变量
	int counter= 0
	void tick(_){
		counter++;
		controller.add(counter);
		//判断计数变量是否达到了最大值
		if(counter == maxCount){
		//关闭计时器
		timer.cancel();
		//关闭Stream并通知监听器
		controller.clase();
		}
	}
//启动计时器
void startTimer(){
	timer = Timer.periodic(interval,tick);
}
void stopTimer(){
if (timer != null){
timer.cancel();
timer = null;
}
print('结束执行');
}
controller = StreamController<int>(
	onListen: startTimer,
	onPause: stopTimer,
	onResume: startTimer,
	onCAncel: stoptimer
);
return controller.stream;
}
void main() async{
Stream<int> stream = createStream(const Duration(senconds:1),10);
	stream.listen((int value){
	print('来自createStream的值:$value');
	});
}

Interable<int> getNumbers(int number) sync* (
	print('开始执行');
	int k=0;
	while(k<number) yield k++;
	print('生成器执行结束');
)
void main (){
print('创建interator');
for (int val in numbers){
print('$val');
}
}

Interable<int> getNumbers(int number) async* (
	print('开始执行');
	int k=0;
	while(k<number) yield k++;
	print('生成器执行结束');
)
void main (){
print('创建interator');
for (int val in numbers){
print('$val');
}
}

Interable<int> getNumberRecursive(int number) sync* (
	print('开始执行,输出number：$number');
	if(numner>0){
		yield* getNumberRecursive(number - 1);
	}
	print('生成器执行结束number:$number');
)
void main (){
print('创建interator');
Interable<int> numbers = getNumberRecursive(3);
for (int val in numbers){
print('$val');
}
}