如何繼續旋轉圖像

Question

有一個按鈕，當我點擊按鈕時，我想旋轉圖像180，但它只適用於我第一次點擊該按鈕時，如何繼續旋轉圖像，謝謝提前？ 下面是我的源代碼：

- (IBAction)touchButton_Refresh { 

photo *photos = [photoArray objectAtIndexhotoIndex]; 
NSData *xmlData = [NSData dataWithContentsOfFilehotos.localPath]; 
UIImage *image; 
if ([xmlData isKindOfClass:[NSData class]]) { 
image = [[UIImage imageWithData:xmlData] retain]; 
} 


SlideItem *slideItemRotate; 


if (toOrientation == 1 || toOrientation == 2) { 
slideItemRotate = [[SlideItem alloc] initWithFrame:CGRectMake(768*photoIndex, 0, 768, 980)]; 
} 
else if (toOrientation == 3 || toOrientation == 4) { 
slideItemRotate = [[SlideItem alloc] initWithFrame:CGRectMake(1024*photoIndex, 0, 1024, 700)]; 
} 


slideItemRotate.photoImageView.image = image; 

CGAffineTransform rotation = CGAffineTransformMakeRotation(3.14159265); 
[slideItemRotate.photoImageView setTransform:rotation]; 

[[[slideScrollView subviews] objectAtIndex:0] removeFromSuperview]; 

[slideScrollView addSubview:slideItemRotate]; 


[slideItemRotate release]; 


} 

Answer 1

你來串聯變換分析，否則你只是一味地應用相同的旋轉（實際上沒有旋轉它更多）。因此，更換這些線路：

CGAffineTransform rotation = CGAffineTransformMakeRotation(3.14159265); 
[slideItemRotate.photoImageView setTransform:rotation]; 

與此：

CGAffineTransform rotation = CGAffineTransformConcat([[slideItemRotate photoImageView] transform], CGAffineTransformMakeRotation(3.14159265)); 
[slideItemRotate.photoImageView setTransform:rotation]; 

這實際上將串聯旋轉並保持圖像周圍旋轉。如果你總是繞180度旋轉，另一種方法是測試身份變換。如果視圖的變換是標識變換，則應用旋轉。如果不是，則將轉換重置爲標識轉換（有效地反轉進程）。