UIView transitionWithView永遠不會轉換到另一張照片

Question

我想在我的應用程序的主頁上做一個像動畫一樣的幻燈片放映。圖像顯示在正確的用戶界面視圖中，但不會轉換爲其他照片。

編輯：嘗試設置變化圖之前的圖像：

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    /*set image before transition */ 
    _slideShow.image = [UIImage imageNamed:@"Slide Show"]; 
    [self fetchSpecies]; 
    [self beginSlideShow]; 

} 

- (void) beginSlideShow{ 
    NSLog(@"Called"); 
    if([imageUrls_ count] < 1){ 
     NSLog(@"EMPTY"); 
     return; 
    } 
    [UIView transitionWithView:_slideShow duration:0.2 options: UIViewAnimationOptionTransitionCrossDissolve animations:^{ 
     int index = arc4random() % [imageUrls_ count]; 
     _slideShow.image = [self getImage:index]; 
     // Account for the case where some images just aren't there 
     while (_slideShow.image == nil) { 
      index = arc4random() % [imageUrls_ count]; 
      _slideShow.image = [self getImage:index]; 
     } 
    } completion:^(BOOL finished) { 
     if (finished){ 
      //logic 
     } 
    }]; 
} 


- (void) fetchSpecies{ 
    NSFetchRequest* request = [NSFetchRequest fetchRequestWithEntityName:@ "Species"]; 
    NSError* error = nil; 
    NSManagedObjectContext* context = [(LeafletAppDelegate*)[[UIApplication sharedApplication] delegate] managedObjectContext]; 
    NSArray* species = [context executeFetchRequest:request error:&error]; 

    if (!species || error) { // nil is an error 

     NSLog(@"error"); 
     // handle error 
    } 

    // Get all the image urls and description to use for the random images 
    imageUrls_ = [[NSMutableArray arrayWithCapacity:100] retain]; 
    imageDescs_ = [[NSMutableArray arrayWithCapacity:100] retain]; 
    NSString *url; 
    NSString *name; 

    for (Species *s in species) { 

     name = [NSString stringWithFormat:@"%@", [s commonNameFirstLast]]; 

     url = [s.ExampleImageLeaf pathForLocalImageUsingThumbnail:YES]; 
     if (url) { 
      [imageUrls_ addObject:url]; 
      [imageDescs_ addObject:[NSString stringWithFormat:@"%@", name]]; 
     } 
     url = [s.ExampleImageFlower pathForLocalImageUsingThumbnail:YES]; 
     if (url) { 
      [imageUrls_ addObject:url]; 
      [imageDescs_ addObject:[NSString stringWithFormat:@"%@", name]]; 
     } 
     url = [s.ExampleImageFruit pathForLocalImageUsingThumbnail:YES]; 
     if (url) { 
      [imageUrls_ addObject:url]; 
      [imageDescs_ addObject:[NSString stringWithFormat:@"%@", name]]; 
     } 
    }  
} 

- (UIImage *) getImage:(NSUInteger)index 
{ 
    // NSLog(@"empty"); 
    NSString *url = [imageUrls_ objectAtIndex:index]; 
    return [UIImage imageWithContentsOfFile:url]; 
} 

我檢查和imageUrls有660元，所以它不是沒有足夠的照片的問題。我會非常感謝任何見解/建議，我對iOS很新。

Answer 1

我拍攝了兩張圖片用於演示目的，並且我已經更改了視圖的標籤上的滑動操作以根據標籤值更改圖片。 imageView從一張照片轉換到另一張照片。下面的代碼給出了slideView是一個UIImageView。

Swift3

內部viewDidLoad方法：

slideView.image = UIImage(named: "image1") 
slideView.tag = 0 

在滑動動作稱爲以下方法：

func beginSlideShow() { 

    UIView.transition(with: slideView, duration: 1.0, options: [.transitionCrossDissolve, .curveEaseOut], animations: { 
     if self.slideView.tag == 1 { 
      self.slideView.image = UIImage(named: "image2") 
     } else { 
      self.slideView.image = UIImage(named: "image1") 
     } 
    }, completion: { (finished: Bool) in 
     if finished { 
      NSLog("animation finished") 
     } 
    }) 
} 

目標C

- (void) beginSlideShow { 

[UIView transitionWithView:_slideView duration:1.0 options: UIViewAnimationOptionTransitionCrossDissolve animations:^{ 
     if (_slideView.tag == 1) { 
      _slideView.image = [UIImage imageNamed:@"image2"]; 
     } else { 
      _slideView.image = [UIImage imageNamed:@"image1"]; 
     } 
    } completion:^(BOOL finished) { 
     if (finished) { 
      NSLog(@"animation finished"); 
     } 
    }]; 
}