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Asked: 2026-06-01T10:54:02+00:00

My app crashed when i trying to change UITextView text. Here is the code:

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My app crashed when i trying to change UITextView text.

Here is the code: (header file):

//
#import <UIKit/UIKit.h>

@interface DetailViewController : UIViewController {

    IBOutlet UIImageView *appImage;
    IBOutlet UILabel *appName;
    IBOutlet UILabel *appDeveloper;
    IBOutlet UILabel *appVersion;
    UIActivityIndicatorView *loading;
    IBOutlet UITextView *appAbout;
    NSString *selectedApp;

}

@property (nonatomic, retain) NSString *selectedApp;
@property (nonatomic, retain) IBOutlet UIImageView *appImage;
@property (nonatomic, retain) IBOutlet UILabel *appName;
@property (nonatomic, retain) IBOutlet UILabel *appDeveloper;
@property (nonatomic, retain) IBOutlet UILabel *appVersion;
@property (nonatomic, retain) UIActivityIndicatorView *loading;
@property (nonatomic, retain) UITextView *appAbout;

@end

implementation file:

- (void)loadData {

    NSString *trimmedString = [selectedApp stringByReplacingOccurrencesOfString:@" " withString:@"%20"];
    self.navigationItem.title = @"Info";
    NSLog(@"%@", trimmedString);
    NSString *website = [NSString stringWithFormat:@"http://shaymargolisapps.x10.mx/send.php?mission=GetNameOfApps&aname=%@", trimmedString]; 
    NSData *dataURL = [NSData dataWithContentsOfURL:[NSURL URLWithString:website]];
    NSString *strResult = [[[NSString alloc] initWithData:dataURL encoding:NSUTF8StringEncoding]autorelease];
    appName.text = strResult;
    NSString *website1 = [NSString stringWithFormat:@"http://shaymargolisapps.x10.mx/send.php?mission=GetDeveloperOfApp&aname=%@", trimmedString]; 
    NSData *dataURL1 = [NSData dataWithContentsOfURL:[NSURL URLWithString:website1]];
    NSString *strResult1 = [[[NSString alloc] initWithData:dataURL1 encoding:NSUTF8StringEncoding]autorelease];
    appDeveloper.text = strResult1;
    NSString *website2 = [NSString stringWithFormat:@"http://shaymargolisapps.x10.mx/send.php?mission=GetVersionOfApp&aname=%@", trimmedString]; 
    NSData *dataURL2 = [NSData dataWithContentsOfURL:[NSURL URLWithString:website2]];
    NSString *strResult2 = [[[NSString alloc] initWithData:dataURL2 encoding:NSUTF8StringEncoding]autorelease];
    appVersion.text = strResult2;
    NSString *website3 = [NSString stringWithFormat:@"http://shaymargolisapps.x10.mx/send.php?mission=GetInfoOfApp&aname=%@", trimmedString];
    NSData *dataURL3 = [NSData dataWithContentsOfURL:[NSURL URLWithString:website3]];
    NSString *strResult3 = [[[NSString alloc] initWithData:dataURL3 encoding:NSUTF8StringEncoding]autorelease];
    NSLog(@"%@", strResult3);
    **appAbout.text = strResult3;**
    NSString *website4 = [NSString stringWithFormat:@"http://shaymargolisapps.x10.mx/send.php?mission=GetImageOfApp&aname=%@", trimmedString];
    NSData *dataURL4 = [NSData dataWithContentsOfURL:[NSURL URLWithString:website4]];
    NSString *strResult4 = [[[NSString alloc] initWithData:dataURL4 encoding:NSUTF8StringEncoding]autorelease];
    NSData* imageData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:strResult4]];
    UIImage* image = [[UIImage alloc] initWithData:imageData];
    [appImage setImage:image];
    [image release];
    [imageData release];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    [loading stopAnimating];
    [loading setHidden:YES];
    [appName setHidden:NO];
    [appDeveloper setHidden:NO];
    [appVersion setHidden:NO];
    [appImage setHidden:NO];
    [appAbout setHidden:NO];

}

My app crashed on appAbout.text = strResult3; line. What am I doing wrong?

loadData is called with [self performSelectorInBackground:@selector(loadData) withObject:nil]; from viewDidLoad

(Xcode 4.4 DP2, iPhone Simulator 5.1, base SDK 4.3)

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1 Answer

  1. Editorial Team

    You must not change UI* objects from a background thread. That has to be done from the main thread.

    You could use gcd to perform the changes on the main thread. Something like this:

    /* ... */
NSString *strResult4 = [[[NSString alloc] initWithData:dataURL4 encoding:NSUTF8StringEncoding]autorelease];
NSData* imageData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:strResult4]];
UIImage* image = [[UIImage alloc] initWithData:imageData];

dispatch_async(dispatch_get_main_queue(), ^{
    self.navigationItem.title = @"Info";
    appName.text = strResult;
    appDeveloper.text = strResult1;
    appVersion.text = strResult2;
    appAbout.text = strResult3;
    [appImage setImage:image];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    [loading stopAnimating];
    [loading setHidden:YES];
    [appName setHidden:NO];
    [appDeveloper setHidden:NO];
    [appVersion setHidden:NO];
    [appImage setHidden:NO];
    [appAbout setHidden:NO];
});

[image release];
[imageData release];
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