How to implement GMUClusterRenderer in Swift

Question

I am using Google Maps API for iOS and want to use marker clustering utility. I figured out how to show clustered markers, but I would like to customize markers. Can someone explain how to set/change icon and title of each marker or clustered markers? An example code would be very helpful.

class POIItem: NSObject, GMUClusterItem {
    var position: CLLocationCoordinate2D
    var name: String!

    init(position: CLLocationCoordinate2D, name: String) {
        self.position = position
        self.name = name
    }
}

class MyRenderer: NSObject, GMUClusterRenderer {
    var mapView: GMSMapView
    var clusterIconGenerator: GMUClusterIconGenerator
    var clusterManager: GMUClusterManager

    init(mapView: GMSMapView, clusterIconGenerator: GMUClusterIconGenerator, clusterManager: GMUClusterManager) {
        self.mapView = mapView
        self.clusterIconGenerator = clusterIconGenerator
        self.clusterManager = clusterManager
    }

    func renderClusters(clusters: [GMUCluster]) {

    }

    func update() {

    }
}

This is what I have so far. I don't know what to do with renderClusters and update functions.

Answer 1

I found a clean solution for clustered markers, on Swift 4, to use a custom image for the cluster with the number of cluster inside:

class MapClusterIconGenerator: GMUDefaultClusterIconGenerator {

    override func icon(forSize size: UInt) -> UIImage {
        let image = textToImage(drawText: String(size) as NSString,
                                inImage: UIImage(named: "cluster")!,
                                font: UIFont.systemFont(ofSize: 12))
        return image
    }

    private func textToImage(drawText text: NSString, inImage image: UIImage, font: UIFont) -> UIImage {

        UIGraphicsBeginImageContext(image.size)
        image.draw(in: CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height))

        let textStyle = NSMutableParagraphStyle()
        textStyle.alignment = NSTextAlignment.center
        let textColor = UIColor.black
        let attributes=[
            NSAttributedStringKey.font: font,
            NSAttributedStringKey.paragraphStyle: textStyle,
            NSAttributedStringKey.foregroundColor: textColor]

        // vertically center (depending on font)
        let textH = font.lineHeight
        let textY = (image.size.height-textH)/2
        let textRect = CGRect(x: 0, y: textY, width: image.size.width, height: textH)
        text.draw(in: textRect.integral, withAttributes: attributes)
        let result = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return result!
    }

}

Than the setup for the cluster manager:

private func setupClustering() {
    guard let mapView = self.mapView else { return }

    let iconGenerator = MapClusterIconGenerator()
    let renderer = MapClusterRenderer(mapView: mapView, clusterIconGenerator: iconGenerator)
    let algorithm = GMUNonHierarchicalDistanceBasedAlgorithm()
    clusterManager = GMUClusterManager(map: mapView, algorithm: algorithm, renderer: renderer)
}

I also used a custom cluster renderer MapClusterRenderer.

Answer 2

I manage to find "clean" solution, even though it's still confusing. But it works!

1) Create .h file "MarkerManager"

    #import <Foundation/Foundation.h>
@import CoreLocation;
#import "GMUClusterItem.h"
#import <GoogleMaps/GoogleMaps.h>


@interface MarkerManager: NSObject

@property (nonatomic) CLLocationCoordinate2D location;
@property (nonatomic, strong) GMSMarker *marker;

@end

2) Go to GMUDefaultClusterRenderer class in Google-Maps-iOS-Utils folder, import MarkerManager.h class find and change this method:

// Returns a marker at final position of |position| with attached |userData|.
// If animated is YES, animates from the closest point from |points|.
- (GMSMarker *)markerWithPosition:(CLLocationCoordinate2D)position
                             from:(CLLocationCoordinate2D)from
                         userData:(id)userData
                      clusterIcon:(UIImage *)clusterIcon
                         animated:(BOOL)animated {
  GMSMarker *marker = [self markerForObject:userData];
  CLLocationCoordinate2D initialPosition = animated ? from : position;
  marker.position = initialPosition;
  marker.userData = userData;
  if (clusterIcon != nil) {
    marker.icon = clusterIcon;
    marker.groundAnchor = CGPointMake(0.5, 0.5);
  }
  //added
  else {
      MarkerManager *data = userData;
      if(data != nil) {
          marker.icon = data.marker.icon;
      }
  }
  //ends here

  marker.zIndex = _zIndex;

  if ([_delegate respondsToSelector:@selector(renderer:willRenderMarker:)]) {
    [_delegate renderer:self willRenderMarker:marker];
  }
  marker.map = _mapView;

  if (animated) {
    [CATransaction begin];
    [CATransaction setAnimationDuration:kGMUAnimationDuration];
    marker.layer.latitude = position.latitude;
    marker.layer.longitude = position.longitude;
    [CATransaction commit];
  }

  if ([_delegate respondsToSelector:@selector(renderer:didRenderMarker:)]) {
    [_delegate renderer:self didRenderMarker:marker];
  }
  return marker;
}

3) Create new swift class, POIItem:

class POIItem: NSObject, GMUClusterItem {
var position: CLLocationCoordinate2D
@objc var marker: GMSMarker!


init(position: CLLocationCoordinate2D, marker: GMSMarker) {
    self.position = position
    self.marker = marker
}
}

4) Extend GMUDefaultClusterRenderer class and override markerWithPosition method:

import Foundation
import UIKit

class CustomMarkers: GMUDefaultClusterRenderer {
    var mapView:GMSMapView?
    let kGMUAnimationDuration: Double = 0.5

    override init(mapView: GMSMapView, clusterIconGenerator iconGenerator: GMUClusterIconGenerator) {

        super.init(mapView: mapView, clusterIconGenerator: iconGenerator)
    }

    func markerWithPosition(position: CLLocationCoordinate2D, from: CLLocationCoordinate2D, userData: AnyObject, clusterIcon: UIImage, animated: Bool) -> GMSMarker {
        let initialPosition = animated ? from : position
        let marker = GMSMarker(position: initialPosition)
        marker.userData! = userData
        if clusterIcon.cgImage != nil {
            marker.icon = clusterIcon
        }
        else {
            marker.icon = self.getCustomTitleItem(userData: userData)

        }
        marker.map = mapView
        if animated
        {
            CATransaction.begin()
            CAAnimation.init().duration = kGMUAnimationDuration
            marker.layer.latitude = position.latitude
            marker.layer.longitude = position.longitude
            CATransaction.commit()
        }
        return marker
    }

    func getCustomTitleItem(userData: AnyObject) -> UIImage {
        let item = userData as! POIItem
        return item.marker.icon!
    }
}

5) In MapViewController init POIItem in generateClusterItems method:

private func generateClusterItems() {

        for object in DataManager.sharedInstance.mapItemsArray {

            let doubleLat = Double(object.latitude)
            let doubleLong = Double(object.longitude)
            let latitude = CLLocationDegrees(doubleLat!)
            let longitude = CLLocationDegrees(doubleLong!)
            let position = CLLocationCoordinate2DMake(latitude, longitude)
            let marker = GMSMarker(position: position)
            let item = POIItem(position: position, marker: marker)
            self.clusterManager.add(item)                
            item.mapItem = object

        }
    }

Inside the for loop you can call:

marker.icon = UIImage(named:"YOUR_IMAGE_NAME")

Now you can set logic to have more then one custom markers.

Answer 3

In Swift 4.2 :

you can use GMUClusterRendererDelegate:

Add this extension to your controller and be sure that your controller is the delegate of GMUClusterRendererDelegate :

willRenderMarker will call each time a marker going to be render (both cluster marker and clusterItemMarker so you can check it by simple if).so you can modify it's icon and etc before showing it to user

extension YourController: GMUClusterRendererDelegate {
    func renderer(_ renderer: GMUClusterRenderer, willRenderMarker marker: GMSMarker) {
        // if your marker is pointy you can change groundAnchor
        marker.groundAnchor = CGPoint(x: 0.5, y: 1)
        if  let markerData = (marker.userData as? PersonMarker) {
           let icon = markerData.imageURL
           marker.iconView = CustomMarkerView(forUrl: url)
        }
    }
}

And PersonMarker is your marker class that subclass NSObject and GMUClusterItem : (you can use default class of GMUClusterItem but if you need some other properties you can subclass it)

class PersonMarker: NSObject, GMUClusterItem {

  var position: CLLocationCoordinate2D
  var imageURL : String?
  var name: String?
  var userdId: String?
  var lastSeen: String?

  init(position: CLLocationCoordinate2D, url: String?, name: String?, userId: String?, lastSeen: String?) {
      self.position = position
      self.imageURL = url
      self.name = name
      self.userdId = userId
      self.lastSeen = lastSeen
  }

}

You can add PersonMarker to your GMUClusterManager like this :

 let position = CLLocationCoordinate2D(latitude: item.latitude!, longitude: item.longitute!)
 let person = PersonMarker(position: position, url: item.user?.avaterUrl, name: item.user?.name, userId: item.user?.userId, lastSeen: item.lastUpdate)
 clusterManager.add(person)