我的CAGradientLayer未显示？

Question

我需要知道我做错了什么。我字面上复制并粘贴到我的代码和梯度不显示。

#import "ViewController.h" 

@interface ViewController() 

@end 

@implementation ViewController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 


    UIView *gradient_view = [[UIView alloc]initWithFrame:self.view.bounds]; 
    CAGradientLayer *gradient_layer = [CAGradientLayer layer]; 
    [gradient_layer setFrame:gradient_view.bounds]; 

    gradient_layer.startPoint = CGPointMake(0, 0); 
    gradient_layer.endPoint = CGPointMake(0, 1); 

    UIColor *top_color = [UIColor redColor]; 
    UIColor *bottom_color = [UIColor blueColor]; 
    [gradient_layer setColors:@[top_color,bottom_color]]; 
    [gradient_view.layer addSublayer:gradient_layer]; 
    [self.view addSubview:gradient_view]; 


} 


- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 


@end 

它只是显示一个白色屏幕。任何人都可以帮助我找出问题所在。导致它现在真的让我感到困扰。

Answer 1

你可能打算踢自己:)

梯度层需要CGColorRef，不是的UIColor：

CGColorRef topRef = [UIColor redColor].CGColor; 
CGColorRef botRef = [UIColor blueColor].CGColor; 

[gradient_layer setColors:@[(__bridge id)topRef, (__bridge id)botRef]];