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event_bus.dart
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event_bus.dart
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import 'package:flutter/material.dart';
import 'package:event_bus/event_bus.dart';
///
/// <pre>
/// author : Wp
/// e-mail : 1101313414@qq.com
/// time : 2019/8/5 5:10 PM
/// desc :
/// version: 1.0
/// </pre>
///
//订阅者回调签名
typedef void EventCallback(arg);
class EventBus {
//私有构造函数
EventBus._internal();
//保存单例
static EventBus _singleton = new EventBus._internal();
//工厂构造函数
factory EventBus()=> _singleton;
//保存事件订阅者队列,key:事件名(id),value: 对应事件的订阅者队列
var _emap = new Map<Object, List<EventCallback>>();
//添加订阅者
void on(eventName, EventCallback f) {
if (eventName == null || f == null) return;
_emap[eventName] ??= new List<EventCallback>();
_emap[eventName].add(f);
}
//移除订阅者
void off(eventName, [EventCallback f]) {
var list = _emap[eventName];
if (eventName == null || list == null) return;
if (f == null) {
_emap[eventName] = null;
} else {
list.remove(f);
}
}
//触发事件,事件触发后该事件所有订阅者会被调用
void emit(eventName, [arg]) {
var list = _emap[eventName];
if (list == null) return;
int len = list.length - 1;
//反向遍历,防止在订阅者在回调中移除自身带来的下标错位
for (var i = len; i > -1; --i) {
list[i](arg);
}
}
}
//定义一个top-level变量,页面引入该文件后可以直接使用bus
var bus = new EventBus();