iOS 过渡动画的实现你好啊！

//
//  ViewController.m
//  test_CAGradientLayer
//
//  Created by admin on 3/4/16.
//  Copyright © 2016 jeffasd. All rights reserved.
//

#import "ViewController.h"
#import "GardView.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    GardView *view = [[GardView alloc] initWithFrame:CGRectMake(100, 300, 500, 50)];
//    view.frame = CGRectMake(100, 30, 50, 50);
    
    [self.view addSubview:view];
    
    [view setProgress:0.6];
    
    [view performAnimation];
    
}

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

@end

//
//  GardView.h
//  test_CAGradientLayer
//
//  Created by admin on 3/4/16.
//  Copyright © 2016 jeffasd. All rights reserved.
//

#import 

@interface GardView : UIView

- (void)setProgress:(CGFloat)value;

- (void)performAnimation;

@end

//
//  GardView.m
//  test_CAGradientLayer
//
//  Created by admin on 3/4/16.
//  Copyright © 2016 jeffasd. All rights reserved.
//

#import "GardView.h"

@interface GardView()

@property (nonatomic, strong) CALayer *maskLayer;
@property (nonatomic, assign) CGFloat progress;

@end

@implementation GardView


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

 Use a horizontal gradient
//CAGradientLayer *layer = (id)[self layer];
//[layer setStartPoint:CGPointMake(0.0, 0.5)];
//[layer setEndPoint:CGPointMake(1.0, 0.5)];
//
 Create colors using hues in +5 increments
//NSMutableArray *colors = [NSMutableArray array];
//for (NSInteger hue = 0; hue