Ios 在集合视图中预加载MKMapView

我在尝试做“标签”体验。每个选项卡都有屏幕宽度，用户可以在每个选项卡之间滑动。一切正常，除了索引为“3”的选项卡上实现了MKMapView

当用户打开应用程序时，集合视图被初始化为索引“1”，并且

索引XPath（行：1，节：0）

问题是，当用户从1->2刷卡时，UI会被阻塞大约一秒钟，然后集合视图会触发

CellForIndexAtdeXPath

调用

IndexXPath（行：2，节：0）

。我在那个索引处尝试“强制”称重传感器，但不幸的是，地图似乎在屏幕上渲染之前就被初始化了。有什么解决办法吗

编辑：

斯威夫特

class TabCell : UICollectionViewCell
{
var nearestView : NearestView?
var stationsView : StationsView?
var stationsMapView : MapView?

override init(frame: CGRect)
{
    super.init(frame: frame)

    let gradient = CAGradientLayer()
    gradient.frame = bounds
    gradient.colors = [UIColor.clear, RuntimeResources.Get(color: .VeryDarkBlue).cgColor]
    layer.insertSublayer(gradient, at: 0)
}

required init?(coder aDecoder: NSCoder)
{
    fatalError("init(coder:) has not been implemented")
}

func SetupNearestView()
{
    if (nearestView != nil)
    {
        return
    }

    nearestView = NearestView(frame: CGRect(x: 0, y: 0, width: frame.width, height: frame.height))
    addSubview(nearestView!)

    addConstraintsWithFormat(format: "H:|[v0]|", views: nearestView!)
    addConstraintsWithFormat(format: "V:|[v0]|", views: nearestView!)

}

func SetupMapView()
{
    if (stationsMapView != nil)
    {
        return
    }

    stationsMapView = MapView(frame: CGRect(x: 0, y: 0, width: frame.width, height: frame.height))
    addSubview(stationsMapView!)

    addConstraintsWithFormat(format: "H:|[v0]|", views: stationsMapView!)
    addConstraintsWithFormat(format: "V:|[v0]|", views: stationsMapView!)
}

func SetupStationsView()
{
    if (stationsView != nil)
    {
       return
    }

    stationsView = StationsView(frame: CGRect(x: 0, y: 0, width: frame.width, height: frame.height))
    addSubview(stationsView!)

    addConstraintsWithFormat(format: "H:|[v0]|", views: stationsView!)
    addConstraintsWithFormat(format: "V:|[v0]|", views: stationsView!)
}
}

斯威夫特地图

import UIKit
import MapKit

class MapView: MKMapView, MKMapViewDelegate
{
private let infoViewHeight = CGFloat(500)
private let FocusZoomLevel = 0.01
private let ZoomLevel = 0.04
private let centerOfSzczecin = CLLocationCoordinate2D(latitude: 53.433345, longitude: 14.544139)
private var infoViewTopConstraint : NSLayoutConstraint?

lazy var mainStationView : UIView = {

    let msv = UIView(frame: CGRect(x: 0, y: 0, width: self.frame.width, height: self.infoViewHeight))
    msv.translatesAutoresizingMaskIntoConstraints = false
    msv.backgroundColor = RuntimeResources.Get(color: .DarkBlue)
    return msv
}()

override init(frame: CGRect)
{
    super.init(frame: frame)
    delegate = self

    // Adding info view
    SetupInfoView()

    // Setting center of map
    let span = MKCoordinateSpanMake(ZoomLevel, ZoomLevel)
    let region = MKCoordinateRegion(center: centerOfSzczecin, span: span)
    setRegion(region, animated: false)
}

required init?(coder aDecoder: NSCoder)
{
    fatalError("init(coder:) has not been implemented")
}

private func SetupInfoView()
{
    addSubview(mainStationView)
    infoViewTopConstraint = mainStationView.topAnchor.constraint(equalTo: self.bottomAnchor)
    infoViewTopConstraint?.isActive = true
    mainStationView.leftAnchor.constraint(equalTo: self.leftAnchor).isActive = true
    mainStationView.rightAnchor.constraint(equalTo: self.rightAnchor).isActive = true
    mainStationView.heightAnchor.constraint(equalToConstant: infoViewHeight).isActive = true
}

}

---

因为您没有重用MapView单元

尝试将地图视图作为

UICollectionViewCell

（在

UIViewController

中）外部的变量加载，并将其作为子视图添加到中的单元格中

在这里，你可以把它从细胞中移除

---

只需将所有mapView代码加载到单元格外，然后使用单元格将地图显示为子视图即可。

如果您的UI被阻止，则说明您在此处出错：cell.SetupMapView（）与预加载无关。对此我不确定。我正在创建新的MapView实例并处理其约束，这里没有额外的工作。无需加载数据、无需绘制注释、无需cpu密集型或阻塞任务。首先，您可以更轻松地添加问题所需的代码。其次，每次调用cell.SetupMapView（）函数cell ForRowaItem时，是否进行检查以避免每次调用cell时重复所有操作？我将在短时间内发布更多代码。确保我做了足够的检查，我的问题在每次应用程序运行时只发生一次。只是添加了一些源代码。你说得对！初始化map的对象确实是CPU密集型的，我在父ViewController的内部创建了这个初始值设定项，并且只将其作为子视图添加到单元格中，现在工作起来非常有魅力。谢谢@马辛很乐意帮忙：）

import UIKit
import MapKit

class MapView: MKMapView, MKMapViewDelegate
{
private let infoViewHeight = CGFloat(500)
private let FocusZoomLevel = 0.01
private let ZoomLevel = 0.04
private let centerOfSzczecin = CLLocationCoordinate2D(latitude: 53.433345, longitude: 14.544139)
private var infoViewTopConstraint : NSLayoutConstraint?

lazy var mainStationView : UIView = {

    let msv = UIView(frame: CGRect(x: 0, y: 0, width: self.frame.width, height: self.infoViewHeight))
    msv.translatesAutoresizingMaskIntoConstraints = false
    msv.backgroundColor = RuntimeResources.Get(color: .DarkBlue)
    return msv
}()

override init(frame: CGRect)
{
    super.init(frame: frame)
    delegate = self

    // Adding info view
    SetupInfoView()

    // Setting center of map
    let span = MKCoordinateSpanMake(ZoomLevel, ZoomLevel)
    let region = MKCoordinateRegion(center: centerOfSzczecin, span: span)
    setRegion(region, animated: false)
}

required init?(coder aDecoder: NSCoder)
{
    fatalError("init(coder:) has not been implemented")
}

private func SetupInfoView()
{
    addSubview(mainStationView)
    infoViewTopConstraint = mainStationView.topAnchor.constraint(equalTo: self.bottomAnchor)
    infoViewTopConstraint?.isActive = true
    mainStationView.leftAnchor.constraint(equalTo: self.leftAnchor).isActive = true
    mainStationView.rightAnchor.constraint(equalTo: self.rightAnchor).isActive = true
    mainStationView.heightAnchor.constraint(equalToConstant: infoViewHeight).isActive = true
}

}