《Cocos 游戏开发实战》5.3 常驻节点与全局管理

addPersistRootNode(node: Node): void;
removePersistRootNode(node: Node): void;
isPersistRootNode(node: Node): boolean;

{
  "__type__": "cc.Node",
  "_name": "PersistRoot",
  "_parent": { "__id__": 1 },
  "_children": [],
  "_components": [ { "__id__": 20 } ]
}

import { _decorator, Component, Node, director, game, Game, sys } from 'cc';
const { ccclass, property } = _decorator;

@ccclass('PersistentRoot')
export class PersistentRoot extends Component {
  @property(Node) transitionMask: Node | null = null;
  @property(Node) audioRoot: Node | null = null;

  private static shared: PersistentRoot | null = null;

  static get instance(): PersistentRoot | null {
    return PersistentRoot.shared;
  }

  onLoad(): void {
    if (PersistentRoot.shared !== null) {
      // 第二个常驻根出现说明启动流程被走了两遍，直接销毁自己
      this.node.destroy();
      return;
    }
    PersistentRoot.shared = this;

    // 关键一步：声明常驻。必须在节点已经挂进场景之后调用
    director.addPersistRootNode(this.node);

    game.on(Game.EVENT_HIDE, this.onHide, this);
    game.on(Game.EVENT_SHOW, this.onShow, this);
    console.log('[PersistentRoot] 已常驻，平台', sys.platform);
  }

  onDestroy(): void {
    game.off(Game.EVENT_HIDE, this.onHide, this);
    game.off(Game.EVENT_SHOW, this.onShow, this);
    if (PersistentRoot.shared === this) PersistentRoot.shared = null;
  }

  private onHide(): void {
    // 切后台：暂停 BGM、把当前进度落盘（见 11.1）
    console.log('[PersistentRoot] 进入后台，自动存档');
  }

  private onShow(): void {
    // 回前台：恢复 BGM、校正时间
    console.log('[PersistentRoot] 回到前台');
  }
}

// src/game/save-manager.ts —— 挂在 PersistRoot 下
import { _decorator, Component, sys } from 'cc';
const { ccclass } = _decorator;

export const SAVE_KEY = 'block-dash.save.v1';

interface SaveData {
  coins: number;
  maxLevel: number;
  lang: string;
}

const DEFAULT_SAVE: SaveData = { coins: 0, maxLevel: 1, lang: 'zh' };

@ccclass('SaveManager')
export class SaveManager extends Component {
  private data: SaveData = { ...DEFAULT_SAVE };
  private dirty = false;

  onLoad(): void {
    this.load();
  }

  load(): void {
    const raw = sys.localStorage.getItem(SAVE_KEY);
    if (raw === null) return;
    try {
      const parsed = JSON.parse(raw) as Partial<SaveData>;
      this.data = { ...DEFAULT_SAVE, ...parsed };
    } catch (e) {
      // 存档损坏时退回默认值，绝不阻断启动
      console.warn('[SaveManager] 存档解析失败，使用默认值', e);
    }
  }

  markDirty(): void {
    this.dirty = true;
  }

  /** 只在切后台或关卡结束时落盘，避免每帧写 localStorage */
  flush(): void {
    if (!this.dirty) return;
    sys.localStorage.setItem(SAVE_KEY, JSON.stringify(this.data));
    this.dirty = false;
  }

  get coins(): number {
    return this.data.coins;
  }
}

import { _decorator, Component, director, Director } from 'cc';
const { ccclass } = _decorator;

@ccclass('GlobalStateBridge')
export class GlobalStateBridge extends Component {
  onEnable(): void {
    // 每次新场景挂载后都要刷新的逻辑，走场景事件，而不是 onLoad
    director.on(Director.EVENT_AFTER_SCENE_LAUNCH, this.refresh, this);
  }

  onDisable(): void {
    director.off(Director.EVENT_AFTER_SCENE_LAUNCH, this.refresh, this);
  }

  private refresh(): void {
    const scene = director.getScene();
    if (scene === null) return;
    // 只有主界面才需要刷新金币 HUD
    if (scene.name === 'main') {
      console.log('[GlobalStateBridge] 刷新主界面 HUD');
    }
  }
}