shouldReuseRoute(future: ActivatedRouteSnapshot, curr: ActivatedRouteSnapshot): boolean {
  // 默认行为
  return future.routeConfig === curr.routeConfig;
}

shouldAttach(route: ActivatedRouteSnapshot): boolean;

retrieve(route: ActivatedRouteSnapshot): DetachedRouteHandle | null;

shouldDetach(route: ActivatedRouteSnapshot): boolean;

store(route: ActivatedRouteSnapshot, detachedTree: DetachedRouteHandle): void;

import { RouteReuseStrategy, DetachedRouteHandle, ActivatedRouteSnapshot } from '@angular/router';
export class RouteStrategyService implements RouteReuseStrategy {
 public static handlers: { [key: string]: DetachedRouteHandle } = {};
 public static deleteRouteSnapshot(path: string): void {
  const name = path.replace(/\//g, '_');
  if (RouteStrategyService.handlers[name]) {
   delete RouteStrategyService.handlers[name];
  }
 }
 /**
  * 判断当前路由是否需要缓存
  * 这个方法返回false时则路由发生变化并且其余方法会被调用
  * @param {ActivatedRouteSnapshot} future
  * @param {ActivatedRouteSnapshot} curr
  * @returns {boolean}
  * @memberof CacheRouteReuseStrategy
  */
 public shouldReuseRoute(future: ActivatedRouteSnapshot, curr: ActivatedRouteSnapshot): boolean {
  return future.routeConfig === curr.routeConfig
   && JSON.stringify(future.params) === JSON.stringify(curr.params);
 }
 /**
  * 当离开当前路由时这个方法会被调用
  * 如果返回 true 则 store 方法会被调用
  * @param {ActivatedRouteSnapshot} route
  * @returns {boolean}
  * @memberof CacheRouteReuseStrategy
  */
 public shouldDetach(route: ActivatedRouteSnapshot): boolean {
  return true;
 }
 /**
  * 将路由写入缓存
  * 在这里具体实现如何缓存 RouteHandle
  * 提供了我们离开的路由和 RouteHandle
  * @param {ActivatedRouteSnapshot} route
  * @param {DetachedRouteHandle} detachedTree
  * @memberof CacheRouteReuseStrategy
  */
 public store(route: ActivatedRouteSnapshot, detachedTree: DetachedRouteHandle): void {
  RouteStrategyService.handlers[this.getPath(route)] = detachedTree;
 }
 /**
  * 路由被导航 如果此方法返回 true 则触发 retrieve 方法
  * 如果返回 false 这个组件将会被重新创建
  * @param {ActivatedRouteSnapshot} route
  * @returns {boolean}
  * @memberof CacheRouteReuseStrategy
  */
 public shouldAttach(route: ActivatedRouteSnapshot): boolean {
  return !!RouteStrategyService.handlers[this.getPath(route)];
 }
 /**
  * 从缓存读取cached route
  * 提供当前路由的参数（刚打开的路由），并且返回一个缓存的 RouteHandle
  * 可以使用这个方法手动获取任何已被缓存的 RouteHandle
  * @param {ActivatedRouteSnapshot} route
  * @returns {(DetachedRouteHandle | null)}
  * @memberof CacheRouteReuseStrategy
  */
 public retrieve(route: ActivatedRouteSnapshot): DetachedRouteHandle | null {
  return RouteStrategyService.handlers[this.getPath(route)] || null;
 }
 private getPath(route: ActivatedRouteSnapshot): string {
  // tslint:disable-next-line: no-string-literal
  const path = route['_routerState'].url.replace(/\//g, '_');
  return path;
 }
}

import { RouteReuseStrategy } from '@angular/router';
import { RouteStrategyService } from '../services/route-strategy.service';

@NgModule({
  ...
  providers: [
    ...
    { provide: RouteReuseStrategy, useClass: RouteStrategyService }
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }