Question

我正在尝试制作“标签”体验。每个标签都有屏幕宽度，用户可以在每个标签之间滑动。一切都运行得很好，除了在索引为“3”的选项卡上实现MKMapView。

当用户打开应用时，集合视图初始化为索引“1”，cellForIndexAtIndexPath也调用IndexPath(row: 1, section: 0)

override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: PageIndentifier, for: indexPath) as! TabCell

    if (indexPath.item == 0)
    {
        cell.SetupNearestView()
        NearestView = cell.nearestView
        NearestView?.Delegate = self
    }

    if (indexPath.item == 1)
    {
        cell.SetupStationsView()
        StationsView = cell.stationsView
        StationsView?.Delegate = self
    }

    if (indexPath.item == 2)
    {
        cell.SetupMapView()
        MapView = cell.stationsMapView
    }

    return cell
}

问题是，当用户从1开始滑动时，用户界面会被阻止大约一秒钟。 2然后为cellForIndexAtIndexPath调用集合视图触发器IndexPath(row: 2, section: 0)。我试图在该索引处“强制”加载单元格但不幸的是，地图似乎在渲染到屏幕之前初始化。有没有解决办法？

编辑：

TabCell.swift

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!)
}
}

MapView.swift

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
}

}

Answer 1

因为您没有重复使用MapView单元格。

尝试将mapView加载为UICollectionViewCell的变量（在UIViewController中），并将其作为子视图添加到collectionView:willDisplayCell:forItemAtIndexPath: <中的单元格中/ p>

并在collectionView:didEndDisplayingCell:forItemAtIndexPath:中，您可以将其从单元格中删除。

只需将您所有的mapView代码加载到单元格之外，然后使用单元格将地图显示为子视图。

在集合视图中预加载MKMapView

1 个答案: