在Angular 2+中，可以通过使用RouteReuseStrategy来解决浏览器后退按钮不重新加载子路由的问题。下面是一个代码示例：

首先，创建一个自定义的路由重用策略类，例如CustomReuseStrategy：

import { ActivatedRouteSnapshot, DetachedRouteHandle, RouteReuseStrategy } from '@angular/router';

export class CustomReuseStrategy implements RouteReuseStrategy {
  private handlers: { [key: string]: DetachedRouteHandle } = {};

  shouldDetach(route: ActivatedRouteSnapshot): boolean {
    return false;
  }

  store(route: ActivatedRouteSnapshot, handle: DetachedRouteHandle | null): void {
    this.handlers[route.routeConfig?.path as string] = handle as DetachedRouteHandle;
  }

  shouldAttach(route: ActivatedRouteSnapshot): boolean {
    return !!route.routeConfig && !!this.handlers[route.routeConfig.path as string];
  }

  retrieve(route: ActivatedRouteSnapshot): DetachedRouteHandle | null {
    if (!route.routeConfig) return null;
    return this.handlers[route.routeConfig.path as string] || null;
  }

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

接下来，在你的AppModule中使用这个自定义的路由重用策略类：

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { RouterModule, RouteReuseStrategy } from '@angular/router';

import { AppComponent } from './app.component';
import { CustomReuseStrategy } from './custom-reuse-strategy';

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, RouterModule.forRoot([...])],
  providers: [{ provide: RouteReuseStrategy, useClass: CustomReuseStrategy }],
  bootstrap: [AppComponent]
})
export class AppModule { }

通过这样配置之后，当用户点击浏览器的后退按钮时，子路由将不会重新加载，而是会复用之前的组件实例。