Google map is showing white screen in iOS when run second time? - ios

Question

I am displaying the google map using Google Maps SDK for iOS. When I start the view controller first time it shows the map fine. But when I goto the view controller second time it does not display the google map. It shows the blank screen. Actually I am passing the address in the google geo coding api from there I am getting the lang & lat then I am displaying the google map.
Code for displaying google map
//
// GmapViewController.m
// MyDex
// Created by Admin on 8/18/15.
// Copyright (c) 2015 com.vastedge. All rights reserved.
#import "GmapViewController.h"
#import "AFNetworking.h"
#import "UIKit+AFNetworking.h"
#import GoogleMaps;
#interface GmapViewController ()
#end
#implementation GmapViewController
{
GMSMapView *mapView_;
NSString *lat;
NSString *lng;
CLLocationDegrees latitude;
CLLocationDegrees longitude;
UIActivityIndicatorView *activityView;
}
-(void)geoCodeAddress
{
NSCharacterSet *doNotWant = [NSCharacterSet characterSetWithCharactersInString:#":/,."];
self.address = [[self.address componentsSeparatedByCharactersInSet: doNotWant] componentsJoinedByString: #""];
NSString *urlString=[NSString stringWithFormat:#"https://maps.googleapis.com/maps/api/geocode/json?address=%#",self.address];
urlString = [urlString stringByAddingPercentEscapesUsingEncoding:
NSUTF8StringEncoding];
AFHTTPRequestOperationManager *manager = [[AFHTTPRequestOperationManager alloc] initWithBaseURL:[NSURL URLWithString:urlString]];
manager.requestSerializer = [AFJSONRequestSerializer serializer];
AFHTTPRequestOperation *operation = [manager GET:urlString parameters:nil
success:^(AFHTTPRequestOperation *operation, id responseObject)
{
NSArray * results = [responseObject objectForKey:#"results"];
NSDictionary *records=[results objectAtIndex:0];
NSDictionary *geometry=[records objectForKey:#"geometry"];
NSLog(#"geomatry is %#",geometry);
NSDictionary *latLong=[geometry objectForKey:#"location"];
lat=[latLong objectForKey:#"lat"];
lng=[latLong objectForKey:#"lng"];
latitude=[lat floatValue];
longitude=[lng floatValue];
NSLog(#"main lat is %f",latitude);
NSLog(#"main lng is %f",longitude);
[self activityIndicator:#"hide"];
[self Loadgmap];
}
failure:^(AFHTTPRequestOperation *operation, NSError *error)
{
NSLog(#"failure string is");
[self activityIndicator:#"hide"];
UIAlertView *alert =[[UIAlertView alloc]initWithTitle:#"Warning" message:#"Unable to display map" delegate:self cancelButtonTitle:#"Ok" otherButtonTitles:nil];
[alert show];
}];
[operation start];
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self activityIndicator:#"show"];
[self geoCodeAddress];
}
-(void)Loadgmap
{
GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:-33.868
longitude:151.2086
zoom:6];
GMSMapView *mapView = [GMSMapView mapWithFrame:CGRectZero camera:camera];
GMSMarker *marker = [[GMSMarker alloc] init];
marker.position = camera.target;
marker.snippet = #"Hello World";
marker.appearAnimation = kGMSMarkerAnimationPop;
marker.map = mapView;
self.view = mapView;
}
-(void)activityIndicator:(NSString *)show
{
if([show isEqual:#"show"])
{
NSLog(#"loading shown");
[[UIApplication sharedApplication] beginIgnoringInteractionEvents];
activityView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
activityView.layer.backgroundColor = [[UIColor colorWithWhite:0.0f alpha:0.5f] CGColor];
activityView.hidesWhenStopped = YES;
activityView.frame = self.view.bounds;
[self.view addSubview:activityView];
[activityView startAnimating];
}
else
{
[[UIApplication sharedApplication] endIgnoringInteractionEvents];
[activityView stopAnimating];
[activityView removeFromSuperview];
}
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
/*
#pragma mark - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
// Get the new view controller using [segue destinationViewController].
// Pass the selected object to the new view controller.
}
*/
#end

Answer 1

Using dispatch_async(dispatch_get_main_queue(), ^{}) is a better practice, but the main problem of your white screen issue is the view in your ViewController get assigned to new value twice.
When the [self Loadgmap] is called in you viewDidLoad(), the self.view = mapView; is called. When your networking required is done, your [self Loadgmap] is called again, and the self.view = mapView; is called again, which make your view become a white screen.
You should only assign value to your view in the viewDidLoad() method, not later in other method calls.
To fix your problem, you can make a new method call -(void)updateMap():
-(void)updateMap {
GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:[lat floatValue]
longitude:[lng floatValue]
zoom:6];
GMSMarker *marker = [[GMSMarker alloc] init];
marker.position = camera.target;
marker.snippet = #"Hello World";
marker.appearAnimation = kGMSMarkerAnimationPop;
marker.map = (GMSMapView*)self.view;
[((GMSMapView*)self.view) animateToCameraPosition:camera];
}
You should call it inside your network request success block:
NSArray * results = [responseObject objectForKey:#"results"];
NSDictionary *records=[results objectAtIndex:0];
NSDictionary *geometry=[records objectForKey:#"geometry"];
NSLog(#"geomatry is %#",geometry);
NSDictionary *latLong=[geometry objectForKey:#"location"];
lat=[latLong objectForKey:#"lat"];
lng=[latLong objectForKey:#"lng"];
latitude=[lat floatValue];
longitude=[lng floatValue];
NSLog(#"main lat is %f",latitude);
NSLog(#"main lng is %f",longitude);
dispatch_async(dispatch_get_main_queue(), ^{
[self activityIndicator:#"hide"];
[self updateMap];
});
Your viewDidLoad() should call [self Loadgmap] first to initialize a Google Map to your view.
- (void)viewDidLoad
{
[super viewDidLoad];
[self activityIndicator:#"show"];
[self Loadgmap];
[self geoCodeAddress];
}
Full code snippet: https://gist.github.com/ziyang0621/f66dd536382b1b16597d