Question

我正在尝试在我的mapView上实现自定义手势识别器，这将阻止用户放大或缩小超过MKCoordinateSpan设置的某个阈值。

mapView的ViewController是选项卡栏Controller的一部分，因此，每当视图消失时，我都会删除mapView，并出于内存目的重新添加它。

自从我添加了“自定义手势识别器”以来，视图消失时不会释放内存。除了从mapView中删除手势识别器之外，我还缺少什么？

MapViewController：

class MapViewController: UIViewController, CLLocationManagerDelegate {

    @IBOutlet var mapView: MKMapView!

    override func viewDidLoad() {
        super.viewDidLoad()
        loadMapView()
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        if mapView == nil {
            loadMapView()
        }
    }

    override func viewDidDisappear(_ animated:Bool) {
        super.viewDidDisappear(animated)
        self.applyMapViewMemoryFix()
    }

    func loadMapView() {
        self.edgesForExtendedLayout = []
        setMapView()
    }

    func setMapView() {
        if self.mapView == nil {
            addMapView()
        }

        mapView.delegate = self
        mapView.mapType = .mutedStandard
        mapView.autoresizingMask = [.flexibleWidth,.flexibleHeight]
    }

    func addMapView() {
        mapView = MKMapView()
        mapView.frame = self.navigationController!.view.bounds
        mapView.mapType = MKMapType.standard
        mapView.isZoomEnabled = true
        mapView.isScrollEnabled = true
        self.view.addSubview(mapView)
    }

    func applyMapViewMemoryFix() {
        for recognizer in (self.mapView?.gestureRecognizers)! {
            if recognizer is WildCardGestureRecognizer {
                self.mapView.removeGestureRecognizer(recognizer)
            }
        }

        self.mapView.showsUserLocation = false
        self.mapView.delegate = nil
        self.mapView.removeFromSuperview()
        self.mapView = nil
    }

}

我在其中为手势识别器设置边界的扩展：

extension MapViewController: MKMapViewDelegate {

    // View Region Changing
    func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) {
        let northernBorder = 32.741152
        let southernBorder = 32.731461
        let easternBorder = -117.143622
        let westernBorder = -117.157399

        var latitude  = mapView.region.center.latitude
        var longitude = mapView.region.center.longitude

        if (mapView.region.center.latitude > northernBorder) {
            latitude = northernBorder
        }

        if (mapView.region.center.latitude <  southernBorder) {
            latitude = southernBorder
        }

        if (mapView.region.center.longitude > easternBorder) {
            longitude = easternBorder
        }

        if (mapView.region.center.longitude < westernBorder) {
            longitude = westernBorder
        }

        let tapInterceptor = WildCardGestureRecognizer(target: nil, action: nil)

        tapInterceptor.touchesBeganCallback = {_, _ in
            mapView.isZoomEnabled = true
        }

        tapInterceptor.touchesMovedCallback = {_, _ in
            if tapInterceptor.scale < 1 {
                if (latitude != mapView.region.center.latitude || longitude != mapView.region.center.longitude)
                    || ((mapView.region.span.latitudeDelta > (northernBorder - southernBorder) )
                        || (mapView.region.span.longitudeDelta > (easternBorder - westernBorder))) {
                    let span = MKCoordinateSpan.init(latitudeDelta: 0.007, longitudeDelta: 0.007)
                    if mapView.region.span.latitudeDelta > span.latitudeDelta || mapView.region.span.longitudeDelta > span.longitudeDelta {
                        mapView.isZoomEnabled = false
                    } else {
                        mapView.isZoomEnabled = true
                    }
                }
            } else if tapInterceptor.scale > 1 {
                let minimumSpan = MKCoordinateSpan.init(latitudeDelta: 0.002, longitudeDelta: 0.002)
                if mapView.region.span.latitudeDelta < minimumSpan.latitudeDelta || mapView.region.span.longitudeDelta < minimumSpan.longitudeDelta {
                    mapView.isZoomEnabled = false
                } else {
                    mapView.isZoomEnabled = true
                }
            }
        }

        tapInterceptor.touchesEndedCallback = {_, _ in
            mapView.isZoomEnabled = true
        }

        mapView.addGestureRecognizer(tapInterceptor)
    }
}

自定义手势识别器：

class WildCardGestureRecognizer: UIPinchGestureRecognizer {

    var touchesBeganCallback: ((Set<UITouch>, UIEvent) -> Void)?
    var touchesMovedCallback: ((Set<UITouch>, UIEvent) -> Void)?
    var touchesEndedCallback: ((Set<UITouch>, UIEvent) -> Void)?

    override init(target: Any?, action: Selector?) {
        super.init(target: target, action: action)
        self.cancelsTouchesInView = false
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesBegan(touches, with: event)
        touchesBeganCallback?(touches, event)
    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesMoved(touches, with: event)
        touchesMovedCallback?(touches, event)
    }

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesEnded(touches, with: event)
        touchesEndedCallback?(touches, event)
    }

    override func canPrevent(_ preventedGestureRecognizer: UIGestureRecognizer) -> Bool {
        return false
    }

    override func canBePrevented(by preventingGestureRecognizer: UIGestureRecognizer) -> Bool {
        return false
    }
}

Answer 1

在此处声明手势时内存泄漏

 let tapInterceptor = WildCardGestureRecognizer(target: nil, action: nil)
 .
 .
 .
 mapView.addGestureRecognizer(tapInterceptor)

在regionDidChangeAnimated内，由于多次调用，随着区域的变化，您会在地图视图中添加许多手势，因此最好创建像

这样的实例变量

var tapInterceptor:WildCardGestureRecognizer!

并在函数内部添加手势init和回调，然后将其称为viewDidLoad

还删除@IBOutle

@IBOutlet var mapView: MKMapView!

如果您不将其放置在Storyboard中，我也不认为删除/添加方式会有所作为，因为IOS中对象的解除分配始终不会释放整个组件，因此最好将mapview与这只是一个手势，而不是在选择/取消选择水龙头

时从丢失的水流中累积大量泄漏

无法从内存堆栈中取消分配手势识别器

1 个答案: