使用背景與基本樣式

有時(shí)候針對(duì)不同平臺(tái)會(huì)使用不同dart庫(kù)/dart文件，這個(gè)時(shí)候就需要根據(jù)平臺(tái)條件import

import ‘default.dart’ if(condition) 'other.dart'

實(shí)際例子1

///默認(rèn)導(dǎo)入庫(kù)是’_api.dart'，如果dart庫(kù)是“dart.library.io”導(dǎo)入’_io.dart'，以此類推。
import '_api.dart' if (dart.library.io) '_io.dart' if (dart.library.html) '_html.dart' as platform;

//最后的as操作
//This way you import all class from ‘***.dart’ and namespaced it with ‘platform’ keyword


class WebSocketHelper {
  /// 暴露 createWebSocketChannel函數(shù)
  static WebSocketChannel createWebSocketChannel(String address) {
    return platform.createWebSocketChannel(address);
  }
}

實(shí)際例子2

import 'dart:async' as async;

void main() {
  async.StreamController controller = new async.StreamController(); // doable
  List data = [1, 2, 3];
  Stream stream = new Stream.fromIterable(data); // not doable because you namespaced it with 'async'
}

例子3（import show）

import 'dart:async' show Stream;

void main() {
  List data = [1, 2, 3];
  Stream stream = new Stream.fromIterable(data); // doable
  StreamController controller = new StreamController(); // not doable because you only show Stream
}