#import <UIKit/UIKit.h>

typedef enum : NSUInteger {

    RPGradientAnimationViewColorDirectionUpToDown               = ,       // 从上到下

    RPGradientAnimationViewColorDirectionLeftToRight            = ,       // 从左到右

    RPGradientAnimationViewColorDirectionDownToUp               = ,       // 从下到上

    RPGradientAnimationViewColorDirectionRightToLeft            = ,       // 从右到左

    RPGradientAnimationViewColorDirectionObliqueLeftToRigth     = ,       // 对角线:左上到右下

    RPGradientAnimationViewColorDirectionObliqueRightToLeft     =         // 对角线:右上到左下

} RPGradientAnimationViewColorDirection;

@interface RPGradientAnimationView : UIImageView

/** 渐变色方向 */

@property (nonatomic, assign) RPGradientAnimationViewColorDirection colorDirection;

/** 颜色 */

@property (nonatomic, strong) UIColor *color;

/** 颜色百分比(非透明部分) 取值范围:0~1 */

@property (nonatomic, assign) CGFloat percent;

@end

#import "RPGradientAnimationView.h"

@interface RPGradientAnimationView ()

// 渐变层

@property (nonatomic, strong) CAGradientLayer *gradientLayer;

// 背景图片

@property (nonatomic, weak) UIImageView *bgImageView;

@end

@implementation RPGradientAnimationView

- (instancetype)init

{

    self = [super init];

    if (self) {

        // 初始化渐变层

        self.gradientLayer = [CAGradientLayer layer];

        // 颜色组

        self.gradientLayer.colors = @[

                                      (id)[UIColor clearColor].CGColor,

                                      (id)[UIColor redColor].CGColor

                                      ];

        // 设置颜色分隔点

        self.gradientLayer.locations = @[@(.f), @(.f)];

        // 设置渐变方向

        self.gradientLayer.startPoint = CGPointMake(, );

        self.gradientLayer.endPoint = CGPointMake(, );

        // 添加渐变层

        [self.layer addSublayer:self.gradientLayer];

    }

    return self;

}

- (void)layoutSubviews

{

    [super layoutSubviews];

    self.gradientLayer.frame = self.bounds;

}

- (void)setColor:(UIColor *)color

{

    _color = color;

    self.gradientLayer.colors = @[

                                  (id)[UIColor clearColor].CGColor,

                                  (id)color.CGColor

                                  ];

}

- (void)setColorDirection:(RPGradientAnimationViewColorDirection)colorDirection

{

    _colorDirection = colorDirection;

    CGPoint startPoint;

    CGPoint endPoint;

    switch (colorDirection) {

        case RPGradientAnimationViewColorDirectionUpToDown:

            startPoint = CGPointMake(, );

            endPoint = CGPointMake(, );

            break;

        case RPGradientAnimationViewColorDirectionLeftToRight:

            startPoint = CGPointMake(, );

            endPoint = CGPointMake(, );

            break;

        case RPGradientAnimationViewColorDirectionDownToUp:

            startPoint = CGPointMake(, );

            endPoint = CGPointMake(, );

            break;

        case RPGradientAnimationViewColorDirectionRightToLeft:

            startPoint = CGPointMake(, );

            endPoint = CGPointMake(, );

            break;

        case RPGradientAnimationViewColorDirectionObliqueLeftToRigth:

            startPoint = CGPointMake(, );

            endPoint = CGPointMake(, );

            break;

        case RPGradientAnimationViewColorDirectionObliqueRightToLeft:

            startPoint = CGPointMake(, );

            endPoint = CGPointMake(, );

            break;

        default:

            startPoint = CGPointMake(, );

            endPoint = CGPointMake(, );

            break;

    }

    self.gradientLayer.startPoint = startPoint;

    self.gradientLayer.endPoint = endPoint;

}

- (void)setPercent:(CGFloat)percent

{

    if (!(percent <  || percent > )) {

        _percent = percent;

        self.gradientLayer.locations = @[@(percent), @(.f)];

    }

}

@end

#import "ViewController.h"

#import "RPGradientAnimationView.h"

#define RPRandomColor [UIColor colorWithRed:(arc4random_uniform(255))/255.0 green:(arc4random_uniform(255))/255.0 blue:(arc4random_uniform(255))/255.0 alpha:1.0]

@interface ViewController ()

@property (nonatomic, strong) NSTimer *timer;

@property (nonatomic, weak) RPGradientAnimationView *gradientAnimationView;

@end

@implementation ViewController

- (void)viewDidLoad

{

    [super viewDidLoad];

    RPGradientAnimationView *gradientAnimationView = [[RPGradientAnimationView alloc] init];

    gradientAnimationView.frame = CGRectMake(, , self.view.frame.size.width, self.view.frame.size.height);

    gradientAnimationView.colorDirection = RPGradientAnimationViewColorDirectionUpToDown;

    gradientAnimationView.color = [UIColor redColor];

    gradientAnimationView.image = [UIImage imageNamed:@"开始图片"];

    gradientAnimationView.contentMode = UIViewContentModeScaleAspectFill;

    [self.view addSubview:gradientAnimationView];

    self.gradientAnimationView = gradientAnimationView;

    self.timer = [NSTimer scheduledTimerWithTimeInterval:.f target:self selector:@selector(startAnimation) userInfo:nil repeats:YES];

}

- (void)startAnimation

{

    self.gradientAnimationView.percent = arc4random() %  / 100.0;

    self.gradientAnimationView.color = RPRandomColor;

}

@end