CircleCollider2D

A circular 2D collider.

Type	Name	Interface Description
Variables	fitImage: boolean	• Function: Gets or sets whether this collider should automatically fit the attached image. When enabled, the runtime can use the image size as input for circle sizing behavior.
Variables	radius: number	• Function: Gets or sets the authored radius of the 2D circle collider. Larger values produce a larger circular collision region.
Functions	constructor()

Examples

constructor()

let obj = new APJS.CircleCollider2D();

Use Case

Example 1 — Tap to drop a ball/coin that bounces multiple times on a static floor — full Physics Matter resource flow (DSL: add_builtin_resource → set_resource_properties →…

@component()
export class TapToDropBouncy extends APJS.BasicScriptComponent {
  private rb: APJS.RigidBody2D | null = null;
  private collider: APJS.CircleCollider2D | null = null;
  private touchCallback: ((event: APJS.IEvent) => void) | null = null;
  private collisionCallback: ((event: APJS.IEvent) => void) | null = null;
  private dropped = false;
  private bounceCount = 0;

  onStart(): void {
    const obj = this.getSceneObject();
    this.rb = obj.getComponent("RigidBody2D") as APJS.RigidBody2D;
    this.collider = obj.getComponent("CircleCollider2D") as APJS.CircleCollider2D;
    if (!this.rb || !this.collider) return;

    // emitCollisionEvent is APJS-runtime-only — must set in onStart, not in DSL.
    this.collider.emitCollisionEvent = true;

    this.touchCallback = (event: APJS.IEvent) => {
      const touch = event.args[0] as APJS.TouchData;
      if (touch.phase === APJS.TouchPhase.Began && !this.dropped && this.rb) {
        this.dropped = true;
        this.rb.static = false;  // gravity now applies
      }
    };
    APJS.EventManager.getGlobalEmitter().on(APJS.EventType.Touch, this.touchCallback);

    this.collisionCallback = (event: APJS.IEvent) => {
      this.bounceCount++;
      // Optional: stop tracking after 5 bounces, or play SFX, or update score, etc.
      if (this.bounceCount === 1) console.log("[Bouncy] first impact");
    };
    const emitter = APJS.EventManager.getObjectEmitter(this.collider);
    emitter.on(APJS.CollisionEvent2D.Enter, this.collisionCallback, this);
  }

  onDestroy(): void {
    if (this.touchCallback) {
      APJS.EventManager.getGlobalEmitter().off(APJS.EventType.Touch, this.touchCallback);
    }
    if (this.collisionCallback && this.collider) {
      APJS.EventManager.getObjectEmitter(this.collider).off(APJS.CollisionEvent2D.Enter, this.collisionCallback, this);
    }
  }
}

Example 2 — Track score via 2D collision events: enable emitCollisionEvent on CircleCollider2D, listen to CollisionEvent2D.Enter via getObjectEmitter, toggle RigidBody2D.st…

@component()
export class CollisionScoreTracker extends APJS.BasicScriptComponent {
  @serializeProperty
  private playerObject: APJS.SceneObject;
  @serializeProperty
  private scoreTextObject: APJS.SceneObject;

  private rigidBody: APJS.RigidBody2D;
  private collider: APJS.CircleCollider2D;
  private scoreText: APJS.Text;
  private score: number = 0;
  private released: boolean = false;

  onStart(): void {
    this.rigidBody = this.playerObject.getComponent("RigidBody2D") as APJS.RigidBody2D;
    this.collider = this.playerObject.getComponent("CircleCollider2D") as APJS.CircleCollider2D;
    this.scoreText = this.scoreTextObject.getComponent("Text") as APJS.Text;
    if (this.rigidBody) this.rigidBody.static = true;
    if (this.collider) {
      this.collider.emitCollisionEvent = true;
      const emitter = APJS.EventManager.getObjectEmitter(this.collider);
      emitter.on(APJS.CollisionEvent2D.Enter, this.onCollision);
    }
    APJS.EventManager.getGlobalEmitter().on(APJS.EventType.Touch, this.onTouch);
    APJS.EventManager.getGlobalEmitter().on(APJS.EventType.RecordStart, this.onRecordStart);
  }

  private onTouch = (event: APJS.IEvent) => {
    const touch = event.args[0] as APJS.TouchData;
    if (touch.phase === APJS.TouchPhase.Began && !this.released) {
      this.released = true;
      if (this.rigidBody) this.rigidBody.static = false;
    }
  };

  private onCollision = (event: APJS.IEvent) => {
    const infos = event.args[0] as APJS.CollisionInfo2D[];
    for (const info of infos) {
      const other = info.otherObject as APJS.SceneObject;
      if (other) {
        this.score++;
        if (this.scoreText) this.scoreText.text = `Score: ${this.score}`;
      }
    }
  };

  private onRecordStart = () => {
    this.score = 0;
    this.released = false;
    if (this.rigidBody) this.rigidBody.static = true;
    if (this.scoreText) this.scoreText.text = "Score: 0";
  };

  onDestroy(): void {
    APJS.EventManager.getGlobalEmitter().off(APJS.EventType.Touch, this.onTouch);
    APJS.EventManager.getGlobalEmitter().off(APJS.EventType.RecordStart, this.onRecordStart);
    if (this.collider) {
      this.collider.emitCollisionEvent = false;
      const emitter = APJS.EventManager.getObjectEmitter(this.collider);
      emitter.off(APJS.CollisionEvent2D.Enter, this.onCollision);
    }
  }
}