《Cocos 游戏开发实战》7.2 碰撞与关卡推进

import { _decorator, Component, PhysicsSystem2D, EPhysics2DDrawFlags, Vec2 } from 'cc';
const { ccclass } = _decorator;

@ccclass('PhysicsBootstrap')
export class PhysicsBootstrap extends Component {
  onLoad(): void {
    const sys2d = PhysicsSystem2D.instance;
    sys2d.enable = true;
    sys2d.gravity = new Vec2(0, -1800);
    // 打开碰撞体线框：Shape 画形状，Aabb 画包围盒，发布前务必关掉
    sys2d.debugDrawFlags = EPhysics2DDrawFlags.Shape | EPhysics2DDrawFlags.Aabb;
    // collisionMatrix 是只读的，只能在编辑器里改，这里读出来只为核对
    console.log('PLAYER row:', sys2d.collisionMatrix['PLAYER']);
  }
}

// assets/scripts/game/collision-router.ts
import { _decorator, Component, Collider2D, Contact2DType, IPhysics2DContact } from 'cc';
const { ccclass, property, disallowMultiple } = _decorator;

/** 接触回调的路由：维护接触计数，并把接触翻译成业务事件。 */
@ccclass('CollisionRouter')
@disallowMultiple
export class CollisionRouter extends Component {
  @property({ tooltip: '当前与之接触的碰撞体数量，>0 即视为落地' })
  contactCount = 0;

  onEnable(): void {
    const cols = this.getComponents(Collider2D);
    for (const c of cols) {
      c.on(Contact2DType.BEGIN_CONTACT, this.onBegin, this);
      c.on(Contact2DType.END_CONTACT, this.onEnd, this);
    }
  }

  private onBegin(self: Collider2D, other: Collider2D, contact: IPhysics2DContact | null): void {
    // 传感器（金币、终点线）只收信息，不产生碰撞响应
    if (other.sensor) return;
    this.contactCount += 1;
  }

  private onEnd(): void {
    this.contactCount = Math.max(0, this.contactCount - 1);
  }

  get grounded(): boolean { return this.contactCount > 0; }
}

// assets/scripts/core/level-progress.ts
export interface LevelResult {
  coins: number;
  coinTotal: number;
  reachedGoal: boolean;
}

export class LevelProgress {
  private collected = 0;
  private readonly coinTotal: number;
  private readonly goalX: number;

  constructor(coinTotal: number, goalX: number) {
    this.coinTotal = coinTotal;
    this.goalX = goalX;
  }

  pickCoin(): void { this.collected += 1; }

  /** scrolledX 是关卡已经向左滚动的距离。 */
  isGoalReached(scrolledX: number): boolean { return scrolledX >= this.goalX; }

  get ratio(): number {
    return this.coinTotal <= 0 ? 0 : this.collected / this.coinTotal;
  }

  snapshot(scrolledX: number): LevelResult {
    return { coins: this.collected, coinTotal: this.coinTotal, reachedGoal: this.isGoalReached(scrolledX) };
  }
}

// assets/scripts/game/hazard.ts
import { _decorator, Component, Collider2D, Contact2DType, IPhysics2DContact, director, sys } from 'cc';
const { ccclass, property } = _decorator;

@ccclass('Hazard')
export class Hazard extends Component {
  @property({ tooltip: '死亡后重新加载的场景名' })
  sceneName = 'main';

  onEnable(): void {
    const col = this.getComponent(Collider2D);
    if (col) col.on(Contact2DType.BEGIN_CONTACT, this.onHit, this);
  }

  private onHit(_self: Collider2D, other: Collider2D, _contact: IPhysics2DContact | null): void {
    if (other.node.name !== 'Player') return;
    // 首次死亡不消耗复活次数，直接重开
    director.loadScene(this.sceneName);
  }
}

// assets/scripts/game/level-scroller.ts
import { _decorator, Component, Vec3, Label } from 'cc';
const { ccclass, property } = _decorator;

@ccclass('LevelScroller')
export class LevelScroller extends Component {
  @property({ tooltip: '滚动速度（像素/秒）' })
  speed = 320;

  @property({ tooltip: '终点线相对起点的距离（像素）' })
  goalX = 4800;

  @property({ type: Label })
  progressLabel: Label | null = null;

  private scrolled = 0;

  update(dt: number): void {
    if (this.scrolled >= this.goalX) return;
    const step = this.speed * dt;
    this.scrolled += step;
    this.node.setPosition(this.node.position.x - step, this.node.position.y, 0);
    if (this.progressLabel) {
      this.progressLabel.string = `${Math.min(100, Math.round((this.scrolled / this.goalX) * 100))}%`;
    }
  }

  get scrolledX(): number { return this.scrolled; }
  get finished(): boolean { return this.scrolled >= this.goalX; }
}

Canvas
├── LevelRoot            (LevelScroller 组件)
│   ├── Player           (Player.prefab 实例, CollisionRouter)
│   ├── Ground           (BoxCollider2D, GROUND 组)
│   ├── Coins            (若干 Coin 实例, CircleCollider2D + Sensor)
│   ├── Hazards          (若干 Spike 实例, BoxCollider2D, HAZARD 组)
│   └── GoalLine         (BoxCollider2D + Sensor, GOAL 组)
└── HUD
    └── ProgressLabel    (Label, 绑到 LevelScroller.progressLabel)

{
  "__type__": "cc.Node",
  "_name": "LevelRoot",
  "_parent": { "__id__": 1 },
  "_children": [ { "__id__": 3 }, { "__id__": 4 }, { "__id__": 5 } ],
  "_components": [ { "__id__": 6 }, { "__id__": 7 } ],
  "_lpos": { "__type__": "cc.Vec3", "x": 480, "y": 270, "z": 0 },
  "_layer": 33554432
}