XCode Prevent UIWebView flashing white screen after Launch Image

Question

I am fairly new to XCode - I'm designing an app with a single view that just displays a UIWebView that loads my jQuery mobile web site.

I have the Default.png and Default@2x.png files for the Launch images in place. When I run the app on my test device or in the emulator, it shows my Launch Image, and then flashes a white screen while the UIWebView loads the first page.

I know that I can change the background color and opacity so it will flash a different color than white, but I would like to prevent the flash altogether. I would like the app to launch, show the Launch image, and not show the UIWebView until the first page has completely loaded. Help?

Answer 1

@ Andreas Volz (and anyone else wondering how I solved the problem of the white "flash")

First, add the name-of-loading-image.png and name-of-loading-image@2x.png files to your Xcode project. The regular image should be 320 x 460, and the @2x image should be 640 x 920.

Then, in my ViewController.h file I added these properties:

@property (nonatomic, retain) UIWebView *webView;
@property(nonatomic, strong) UIImageView *loadingImageView;
@end

And then in my ViewController.m file I added this:

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController;

@synthesize webView;
@synthesize loadingImageView;

- (void)viewDidLoad
{
    [super viewDidLoad];


    //**************** Set website URL for UIWebView
    [webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.example.com"] cachePolicy:NSURLCacheStorageAllowed timeoutInterval:20.0]];


    //**************** Add Static loading image to prevent white "flash" ****************/  
    UIImage *loadingImage = [UIImage imageNamed:@"name-of-loading-image.png"];
    loadingImageView = [[UIImageView alloc] initWithImage:loadingImage];
        loadingImageView.animationImages = [NSArray arrayWithObjects:
                                            [UIImage imageNamed:@"name-of-loading-image.png"],
                                            nil];
    [self.view addSubview:loadingImageView];   

}

- (void)webViewDidFinishLoad:(UIWebView *)webView {

    // Remove loading image from view
    [loadingImageView removeFromSuperview];

}

Answer 2

To know when your webView has finished loading, you must implement the UIWebViewDelegate protocol.

In your viewController's .h file:

@interface viewController : UIViewController <UIWebViewDelegate>
{
    UIWebView *webView;
}
@end

Then in your viewController's .m file, add this method:

- (void)webViewDidFinishLoad:(UIWebView *)webView {

    NSLog(@"content loading finished");
    // Display your webView
    [self.view addSubview:webView];

}

You can use the -viewDidLoad method in your viewController's .m to continue displaying your launch image. You can also begin the loading of content for your webView:

- (void)viewDidLoad {
    [super viewDidLoad];

    // continue to display launch image
    UIImage *launchImage = [[UIImage alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"launchImage.png" ofType:nil ]];
    UIImageView *launchImageView = [[[UIImageView alloc] initWithImage:launchImage] autorelease];
    [self.view addSubview:launchImageView];

    // now setup the base view for the webView controller
    UIView *contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    contentView.backgroundColor = [UIColor blueColor];

    // for rotation
    contentView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight);
    self.view = contentView;

    //create a frame to size and place the web view
    CGRect webFrame = [[UIScreen mainScreen] applicationFrame];
    UIWebView *aWebView = [[UIWebView alloc] initWithFrame:webFrame];
    self.webView = aWebView;

    //aWebView.scalesPageToFit = YES;
    aWebView.autoresizesSubviews = YES;
    aWebView.autoresizingMask=(UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth);

    //set the web view delegates for the web view to be itself
    [aWebView setDelegate:self];

    //determine the path the to the index.html file in the Resources directory
    NSURL *url = [[NSBundle mainBundle] URLForResource:@"index" withExtension:@"html"];
    NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];
    [aWebView loadRequest:requestObj];
}