RealityKit中ARView多点触摸失效问题求解决方案

我需要通过touchesMoved函数检测双指操作，代码会打印触摸点数量。该程序在普通UIView中可正常运行（打印touches.count=2），但在ARView中始终显示touches.count=1，请问有什么解决办法？

用户提供的测试代码：

import UIKit
import RealityKit

class GameViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.isMultipleTouchEnabled = true

//        // 这段代码可正常检测双指
//        let v = UIView(frame: view.frame)
//        v.backgroundColor = .green
//        view.addSubview(v)
//        v.isMultipleTouchEnabled = true

        // 这段代码无法检测双指
        let arView = ARView(frame: view.frame,
                            cameraMode: .nonAR,
                            automaticallyConfigureSession: true)
        view.addSubview(arView)
        arView.isMultipleTouchEnabled = true        
    }
    
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        print("touchesBegan, touches.count=\(touches.count)")
    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        print("touchesMoved, touches.count=\(touches.count)")
    }

}

解决办法 #

1. 自定义ARView子类重写触摸方法 #

ARView的内部视图层级会拦截触摸事件，导致ViewController无法接收到完整的触摸集合。直接在ARView子类中重写触摸方法，能确保捕获到所有触摸点：

import UIKit
import RealityKit

class CustomARView: ARView {
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)
        print("touchesBegan, touches.count=\(touches.count)")
    }
    
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesMoved(touches, with: event)
        print("touchesMoved, touches.count=\(touches.count)")
    }
}

然后在ViewController中替换为自定义子类：

class GameViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        view.isMultipleTouchEnabled = true
        
        let arView = CustomARView(frame: view.frame,
                                  cameraMode: .nonAR,
                                  automaticallyConfigureSession: true)
        view.addSubview(arView)
        arView.isMultipleTouchEnabled = true
    }
}

2. 禁用ARView默认手势（可选） #

ARView默认自带捏合、旋转等手势识别器，这些手势会抢占触摸事件。如果不需要默认手势，可以禁用它们：

// 创建ARView后添加以下代码
arView.enableTranslateGestures = false
arView.enableRotateGestures = false
arView.enableScaleGestures = false

3. 确保所有子视图启用多触摸 #

递归设置ARView及其所有子视图的isMultipleTouchEnabled和isUserInteractionEnabled为true，避免子视图拦截触摸事件：

// 定义递归函数
func enableFullMultipleTouch(for view: UIView) {
    view.isMultipleTouchEnabled = true
    view.isUserInteractionEnabled = true
    view.subviews.forEach { enableFullMultipleTouch(for: $0) }
}

// 在添加ARView后调用
enableFullMultipleTouch(for: arView)

内容的提问来源于stack exchange，提问作者Tony