南通装饰网站建设,长安镇做网站,版面设计的基本元素是指,手机网站开发软件有哪些async 和 await
Future 链式调用 更清晰异步操作依赖关系比较复杂 可使用async awaitasync await 调用逻辑更清晰async await 异常处理 try{}catch(){} 即可async 修饰的方法 总是返回Future对象 不会阻塞主线程await 关键字只有在async修饰的方法内才有效都是把事件交给 Even…async 和 await
Future 链式调用 更清晰异步操作依赖关系比较复杂 可使用async awaitasync await 调用逻辑更清晰async await 异常处理 try{}catch(){} 即可async 修饰的方法 总是返回Future对象 不会阻塞主线程await 关键字只有在async修饰的方法内才有效都是把事件交给 EventLoop
登录流程Future写法
void main() {Future.value([username,password]).then((value){login(value[0],value[1]);print(${DateTime.now().millisecondsSinceEpoch} 登录中...);sleep(Duration(seconds: 5));return {id: 10001,name: John,classGrade: 三年二班,birthday: 2005-12-12 12:12:12, age: 30};}).then((value){return value;}).then((value){print(${DateTime.now().millisecondsSinceEpoch} value); //jsonvar json jsonDecode(value);int id json[id];getUserInfo(id);print(${DateTime.now().millisecondsSinceEpoch} 获取用户信息...);sleep(Duration(seconds: 5));return 成功,缓存数据跳转首页;}).catchError((value){}).whenComplete((){print(登录流程结束!);});
}login(String username,String password){print(${DateTime.now().millisecondsSinceEpoch} ${username}请求登录!);
}
getUserInfo(int id){print(${DateTime.now().millisecondsSinceEpoch} ${id}获取用户信息!);
}运行结果
1703727827384 username请求登录!
1703727827384 登录中...
1703727832400 {id: 10001,name: John,classGrade: 三年二班,birthday: 2005-12-12 12:12:12, age: 30}
1703727832418 10001获取用户信息!
1703727832418 获取用户信息...
登录流程结束!async/await 写法 import dart:convert;
import dart:io;void main() async{var loginResult await login(aaa, 123);var userInfo await getUserInfo(loginResult);print(userInfo);
}FutureString login(String username,String password){print(${DateTime.now().millisecondsSinceEpoch} ${username}请求登录!);return Future.value([username,password]).then((value){print(${DateTime.now().millisecondsSinceEpoch} 登录中...);sleep(Duration(seconds: 5));return {id: 10001,name: John,classGrade: 三年二班,birthday: 2005-12-12 12:12:12, age: 30};}).then((value){return value;});
}
FutureString getUserInfo(String value){return Future((){print(${DateTime.now().millisecondsSinceEpoch} value); //jsonvar json jsonDecode(value);print(${DateTime.now().millisecondsSinceEpoch} 获取用户信息...);sleep(Duration(seconds: 5));return 成功,缓存数据跳转首页;});
}请求结果
1703727905612 aaa请求登录!
1703727905617 登录中... //5s等待返回结果
1703727910642 {id: 10001,name: John,classGrade: 三年二班,birthday: 2005-12-12 12:12:12, age: 30}
1703727910660 获取用户信息... //5s等待
1703727915670 成功,缓存数据跳转首页 async 修饰的方法 总是返回Future对象 不会阻塞主线程
import dart:convert;
import dart:io;void main(){var login startLogin();print(login.runtimeType${login.runtimeType});
}startLogin() async{var loginResult await login(aaa, 123);var userInfo await getUserInfo(loginResult);print(${DateTime.now().millisecondsSinceEpoch} userInfo);
}FutureString login(String username,String password){return Future.value([username,password]).then((value){print(${DateTime.now().millisecondsSinceEpoch} 登录中...);sleep(Duration(seconds: 5));return {id: 10001,name: John,classGrade: 三年二班,birthday: 2005-12-12 12:12:12, age: 30};}).then((value){return value;});
}
FutureString getUserInfo(String value){return Future((){print(${DateTime.now().millisecondsSinceEpoch} value); //jsonvar json jsonDecode(value);print(${DateTime.now().millisecondsSinceEpoch} 获取用户信息...);sleep(Duration(seconds: 5));return 成功,缓存数据跳转首页;});
}结果
login.runtimeTypeFuturedynamic //类型是Futureawait 关键字只有在async修饰的方法内才有效
