我创建了一个新项目。在LinkedIn中QuartzCore.framework并进口<QuartzCore/QuartzCore.h> in the ViewController.m.
这是代码。
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(@"view height %f", self.view.frame.size.height); // returns 667 on iPhone 6
NSLog(@"view width %f", self.view.frame.size.width); // returns 375 on iPhone 6
NSLog(@"layers count %lu", self.view.layer.sublayers.count); // returns 2
// Gradient
UIColor *colorOne = [UIColor blueColor];
UIColor *colorTwo = [UIColor greenColor];
NSArray *colorArray = @[colorOne, colorTwo];
NSNumber *locationOne = [NSNumber numberWithFloat:0.0];
NSNumber *locationTwo = [NSNumber numberWithFloat:1.0];
NSArray *locationArray = @[locationOne, locationTwo];
CAGradientLayer *gradientLayer = [CAGradientLayer layer];
gradientLayer.frame = self.view.frame;
gradientLayer.colors = colorArray;
gradientLayer.locations = locationArray;
[self.view.layer insertSublayer:gradientLayer atIndex:0];
//[self.view.layer insertSublayer:gradientLayer above:[self.view.layer.sublayers firstObject]]; // didn't work either
NSLog(@"layers count %lu", self.view.layer.sublayers.count); //returns 3
}
我尝试将视图的背景颜色设置为clearColor，将其称为viewDidAppear，但没有一个起作用。我真的不知道我错过了什么。感谢任何帮助。
你的颜色数组应该是NSArray *colorArray = @[(id)colorOne.CGColor, (id)colorTwo.CGColor];，因为colors数组需要CGColorRefs，而不是UIColors，够烦人的 - 看看CGGradientLayer 文档 https://developer.apple.com/library/mac/documentation/GraphicsImaging/Reference/CAGradientLayer_class/#//apple_ref/occ/instp/CAGradientLayer/startPoint
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