目標C - 上UICollectionView

Question

的左/右側褪色梯度I具有水平滾動視圖控制器的，像這樣的主視圖（灰色是UIView的，木材是UICollectionView）內UICollectionView：

我想在這個UICollectionView的最左邊的最左邊添加固定的漸變漸變，以便在用戶滾動時滾動看起來消失。我會如何去做這件事？它是否涉及到CAGradientLayer的某些用途？我會很感激你能給我的任何幫助！

Answer 1

嘗試添加CAGradientLayer兩層的集合視圖子層：

#import <QuartzCore/QuartzCore.h> 

CAGradientLayer *leftShadow = [CAGradientLayer layer]; 
leftShadow.frame = CGRectMake(0, 0, 100, self.collectionView.frame.size.height); 
leftShadow.startPoint = CGPointMake(0, 0.5); 
leftShadow.endPoint = CGPointMake(1.0, 0.5); 
leftShadow.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithWhite:0.0 alpha:0.4f] CGColor], (id)[[UIColor clearColor] CGColor], nil]; 

[self.collectionView.layer addSublayer:leftShadow]; 

CAGradientLayer *rightShadow = [CAGradientLayer layer]; 
rightShadow.frame = CGRectMake(CGRectGetWidth(self.collectionView.frame)-100.0, 0, 100, self.collectionView.frame.size.height); 
rightShadow.startPoint = CGPointMake(1.0, 0.5); 
rightShadow.endPoint = CGPointMake(0, 0.5); 
rightShadow.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithWhite:0.0 alpha:0.4f] CGColor], (id)[[UIColor clearColor] CGColor], nil]; 

[self.collectionView.layer addSublayer:rightShadow]; 

Answer 2

我實際上設法想出解決辦法使用一個遮罩層感謝this tutorial at cocoanetics。下面是我所做的：

@interface ScalesViewController : UIViewController 
{ 
    CAGradientLayer *maskLayer; 
} 
@end 

然後在.M，我放在以下：

- (void)viewDidAppear:(BOOL)animated 
{ 

    [super viewWillAppear: animated]; 

    if (!maskLayer) 
    { 
     maskLayer = [CAGradientLayer layer]; 

     CGColorRef outerColor = [[UIColor colorWithWhite:0.0 alpha:1.0] CGColor]; 
     CGColorRef innerColor = [[UIColor colorWithWhite:0.0 alpha:0.0] CGColor]; 

     maskLayer.colors = [NSArray arrayWithObjects: 
          (__bridge id)outerColor, 
          (__bridge id)innerColor, 
          (__bridge id)innerColor, 
          (__bridge id)outerColor, nil]; 

     maskLayer.locations = [NSArray arrayWithObjects: 
           [NSNumber numberWithFloat:0.0], 
           [NSNumber numberWithFloat:0.125], 
           [NSNumber numberWithFloat:0.875], 
           [NSNumber numberWithFloat:1.0], nil]; 

     [maskLayer setStartPoint:CGPointMake(0, 0.5)]; 
     [maskLayer setEndPoint:CGPointMake(1, 0.5)]; 

     maskLayer.bounds = self.mainCollectionView.bounds; 
     maskLayer.anchorPoint = CGPointZero; 

     [self.mainCollectionView.layer insertSublayer: maskLayer atIndex: 0]; 
    } 
} 

這將創建一個漂亮的「黑漸變」我的收藏鑑於雙方的影響。可以將更多顏色添加到位置&顏色屬性以優化漸變混合。起點/終點確定梯度的方向和位置。