尝试更改UITextView.text时应用程序崩溃

Question

我的应用程序在尝试更改UITextView文本时崩溃。

这是代码：（头文件）：

//
#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

实现文件：

- (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];
}

我的应用程序在appAbout.text = strResult3;线上崩溃。我做错了什么？

loadData使用[self performSelectorInBackground:@selector(loadData) withObject:nil];从viewDidLoad 调用

（Xcode 4.4 DP2，iPhone模拟器5.1，基本SDK 4.3）

Answer 1

您不能从后台线程更改UI*对象。这必须从主线程开始。

您可以使用gcd在主线程上执行更改。类似这样的东西：

/* ... */
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];