Automatic Layout of IOS Layer & quot;

"Automatic Layout" of IOS Layer"

 

Today, when I answered a question to a foreign friend on stackoverflow, I encountered the problem of automatic Layer layout. Write it here and share it with the people you need.

Does Layer Support autolayout?

Currently, ios CALayer does not support AutoLayout or autoresizingMask.

For example

If you want to draw a gradient color as the background color. Define a configuration function

-(void)setupCAGradientLayer:(CAGradientLayer *)gradient{    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];    gradient.colors = colors;    gradient.locations = locations;}

If you do not use an image as the background, you can use a Layer to draw the image directly.
Easy to draw

#import ViewController.h@interface ViewController ()@property (strong,nonatomic) CAGradientLayer * gradient;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    self.gradient = [CAGradientLayer layer];    [self setupCAGradientLayer:self.gradient];    self.gradient.frame = self.view.frame;    [self.view.layer addSublayer:self.gradient];}

However, the screen is incorrect.

Rough Solution

The most intuitive solution is to adjust the layer size when the view bounds is changed.
The code is very simple. When the view bounds changes, the corresponding controller calls viewDidLayoutSubviews.
Therefore, add the following code to the viewController,

-(void)viewDidLayoutSubviews{    [super viewDidLayoutSubviews];    self.gradient.frame = self.view.bounds;}

Normal horizontal screen

However, we all know that IOS will automatically generate an animation when switching between the horizontal and vertical screens. If a rough solution is used, the frame is changed after the animation ends, while the animation is still blank

Good Solution

Because IOS supports view well, it is convenient to use auto layout or autoresizingmask. Therefore, a better solution is to use view for processing.

Bind layer to view
Define a view and set its layer class to CAGradientClass.

#import 
  
   @interface BackgrundView : UIView@end
  

#import BackgrundView.h@interface BackgrundView()@end@implementation BackgrundView+(Class)layerClass{    return [CAGradientLayer class];}@end

Then, use this view to set autoresizingmask

#import ViewController.h#import BackgrundView.h@interface ViewController ()@property BackgrundView * backgroundview;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    self.backgroundview = [[BackgrundView alloc] initWithFrame:self.view.frame];    self.backgroundview.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;    [self.view addSubview:self.backgroundview];    [self setupCAGradientLayer:(CAGradientLayer*)self.backgroundview.layer];   }@end

Let's take a look at the switched animation (the gif is a bit watermark, sorry)