【发布时间】：2014-01-13 07:09:20
【问题描述】：
目标是在导航控制器视图的左侧添加一条阴影线，当视图向右滑动时可以看到。
但相同的代码（版本 1 和 2）适用于 iOS 6 和 5。
所有代码都放在-(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
版本 1
CALayer *navigationViewLayer = [[[self navigationController] view] layer];
CGPathRef path = [[UIBezierPath bezierPathWithRect:[[[self navigationController] view] bounds]] CGPath];
[navigationViewLayer setShadowPath:path];
[navigationViewLayer setShouldRasterize:YES]; // rasterize save the effort of drawing every time by caching
[navigationViewLayer setRasterizationScale:[[UIScreen mainScreen] scale]]; // Have to set rasterization scale for retina screen
[navigationViewLayer setMasksToBounds:NO];
[navigationViewLayer setShadowRadius:5.0f];
[navigationViewLayer setShadowOpacity:1.0f];
[navigationViewLayer setShadowColor:[[UIColor blackColor] CGColor]];
[navigationViewLayer setShadowOffset:CGSizeMake(0.0f, 0.0f)];
版本 2
CGRect screenBoundsRect = [[UIScreen mainScreen] bounds];
CGRect rect = CGRectZero;
rect.origin.x = -4; // SHADOW_LINE_WIDTH
rect.origin.y = 0;
rect.size.width = 4; // SHADOW_LINE_WIDTH
rect.size.height = screenBoundsRect.size.height;
UIImageView *shadowLineImageView = [[UIImageView alloc] initWithFrame:rect];
CAGradientLayer *gradient = [CAGradientLayer layer];
[gradient setFrame:[shadowLineImageView bounds]];
[gradient setStartPoint:CGPointMake(1.0, 0.5)]; // default to (0.5, 0.0)
[gradient setEndPoint:CGPointMake(0.0, 0.5)]; // default to (0.5, 1.0)
[gradient setColors:[NSArray arrayWithObjects:(id)[[UIColor colorWithRed:140/255.f green:140/255.f blue:140/255.f alpha:1.0f] CGColor],
(id)[[UIColor colorWithRed:189/255.f green:189/255.f blue:189/255.f alpha:0.0f] CGColor], nil]]; // color RGB values are optimized by test
[[shadowLineImageView layer] insertSublayer:gradient atIndex:0];
[shadowLineImageView setAlpha:1.0f];
[[[self navigationController] view] addSubview:shadowLineImageView];
[shadowLineImageView autorelease];
截图
图 1. 第 1 版适用于 iOS 6 模拟器：
图 2. 版本 1 适用于 iOS 5 iPhone 4：
图 3. 版本 1 不适用于 iOS 7 模拟器：
图 4. 第 2 版适用于 iOS 6 模拟器：
图 5. 第 2 版适用于 iOS 5 iPhone 4：
图 6. 版本 2 不适用于 iOS 7 模拟器：
【问题讨论】：
标签： objective-c ios7 layer