CALayer 背景颜色

Question

我有一个 CALayer 背景使用：

CAGradientLayer *bgLayer = [BackgroundLayer blueGradient];
bgLayer.frame = self.view.bounds;
[self.view.layer insertSublayer:bgLayer atIndex:0];

在

- (void)prepareToRotate:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration

我用这条线来旋转 CALayer 背景。

[[[self.view.layer sublayers] objectAtIndex:0] setFrame:self.view.bounds];

我得到了一些不漂亮的撕裂效果，因为图层似乎旋转得不够快，我该如何解决这个问题并在旋转时获得无缝效果，有没有更好的方法来调整 calayer 的大小？

谢谢，

编辑：我的所有代码：

.h:

#import <Foundation/Foundation.h>
#import <QuartzCore/QuartzCore.h>


@interface BackgroundLayer : NSObject

+(CAGradientLayer*) greyGradient;
+(CAGradientLayer*) blueGradient;

@end

.m

#import "BackgroundLayer.h"

@implementation BackgroundLayer

//Metallic grey gradient background
+ (CAGradientLayer*) greyGradient {

UIColor *colorOne       = [UIColor colorWithWhite:0.9 alpha:1.0];
UIColor *colorTwo       = [UIColor colorWithHue:0.625 saturation:0.0 brightness:0.85 alpha:1.0];
UIColor *colorThree     = [UIColor colorWithHue:0.625 saturation:0.0 brightness:0.7 alpha:1.0];
UIColor *colorFour      = [UIColor colorWithHue:0.625 saturation:0.0 brightness:0.4 alpha:1.0];

NSArray *colors =  [NSArray arrayWithObjects:(id)colorOne.CGColor, colorTwo.CGColor, colorThree.CGColor, colorFour.CGColor, nil];

NSNumber *stopOne       = [NSNumber numberWithFloat:0.0];
NSNumber *stopTwo       = [NSNumber numberWithFloat:0.02];
NSNumber *stopThree     = [NSNumber numberWithFloat:0.99];
NSNumber *stopFour      = [NSNumber numberWithFloat:1.0];

NSArray *locations = [NSArray arrayWithObjects:stopOne, stopTwo, stopThree, stopFour, nil];

CAGradientLayer *headerLayer = [CAGradientLayer layer];
headerLayer.colors = colors;
headerLayer.locations = locations;

return headerLayer;
}

//Blue gradient background
+ (CAGradientLayer*) blueGradient {
  UIColor *colorOne = [UIColor colorWithRed:(120/255.0) green:(135/255.0) blue:(150/255.0)   alpha:1.0];
  UIColor *colorTwo = [UIColor colorWithRed:(57/255.0)  green:(79/255.0)  blue:(96/255.0)  alpha:1.0];

NSArray *colors = [NSArray arrayWithObjects:(id)colorOne.CGColor, colorTwo.CGColor, nil];

NSNumber *stopOne = [NSNumber numberWithFloat:0.0];
NSNumber *stopTwo = [NSNumber numberWithFloat:1.0];

NSArray *locations = [NSArray arrayWithObjects:stopOne, stopTwo, nil];

CAGradientLayer *headerLayer = [CAGradientLayer layer];
headerLayer.colors = colors;
headerLayer.locations = locations;

return headerLayer;

}

@end

准备旋转只是由

调用

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation
{
    [self prepareToRotate:[[UIApplication sharedApplication] statusBarOrientation] duration:0];

}

只包含

[[[self.view.layer sublayers] objectAtIndex:0] setFrame:self.view.bounds];

Answer 1

我建议在 CoreGraphics 上使用 CAGradientLayer。渲染速度要快得多。对于您的问题，请尝试在旋转之前栅格化您的视图。

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
    self.bgLayer.shouldRasterize = YES;
}

实际上，你可以添加一个子视图而不是一个新层。

@interface MyView : UIView

@end

@implementation MyView

+ (Class)layerClass
{
    return [CAGradientLayer class];
}

@end

在旧的插入层部分，改为执行以下操作。

MyView *bgView = [[MyView alloc] initWithFrame:self.view.bounds];
[(CAGradientLayer *)bgView.layer setColors:colors];
bgView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;

[self.view insertSubview:bgView atIndex:0];

（如果需要，您可以使用自动布局）

Answer 2

Coregraphics 渐变层比 CALayer 好得多。 CALayer 很慢并且会显示渐变带，而 coregraphics 将具有平滑的渐变。这可能就是它发生在你身上的原因。

创建一个 -(void)drawRect:(CGRect)rect { 函数并在下面绘制渐变。它应该照顾你的问题。

这里有很多示例代码。这里有一些

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat locations[] = { 0.0, 1.0 };

NSArray *colors = @[(__bridge id) startColor, (__bridge id) endColor];

CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) colors, locations);