iOS 过渡动画的实现

////  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 <UIKit/UIKit.h>@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 <= 360; hue += 5) {//    //    UIColor *color;//    color = [UIColor colorWithHue:1.0 * hue / 360.0//                       saturation:1.0//                       brightness:1.0//                            alpha:1.0];//    [colors addObject:(id)[color CGColor]];//}////[layer setColors:[NSArray arrayWithArray:colors]];- (instancetype)initWithFrame:(CGRect)frame{        self = [super initWithFrame:frame];        if (self != nil) {                _maskLayer = [CALayer layer];        [_maskLayer setFrame:CGRectMake(0, 0, 0, frame.size.height)];        [_maskLayer setBackgroundColor:[[UIColor blackColor] CGColor]];        [self.layer setMask:_maskLayer];                // 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 <= 360; hue += 5) {                        UIColor *color;            color = [UIColor colorWithHue:1.0 * hue / 360.0                               saturation:1.0                               brightness:1.0                                    alpha:1.0];            [colors addObject:(id)[color CGColor]];         }         [layer setColors:[NSArray arrayWithArray:colors]];    }        return self;}- (void)performAnimation {    // Move the last color in the array to the front    // shifting all the other colors.    CAGradientLayer *layer = (id)[self layer];    NSMutableArray *mutable = [[layer colors] mutableCopy];    id lastColor = [mutable lastObject] ;    [mutable removeLastObject];    [mutable insertObject:lastColor atIndex:0];    NSArray *shiftedColors = [NSArray arrayWithArray:mutable];        // Update the colors on the model layer    [layer setColors:shiftedColors];        // Create an animation to slowly move the gradient left to right.    CABasicAnimation *animation;    animation = [CABasicAnimation animationWithKeyPath:@"colors"];    [animation setToValue:shiftedColors];    [animation setDuration:0.08];    [animation setRemovedOnCompletion:YES];    [animation setFillMode:kCAFillModeForwards];    [animation setDelegate:self];    [layer addAnimation:animation forKey:@"animateGradient"];}- (void)animationDidStop:(CAAnimation *)animation finished:(BOOL)flag {    [self performAnimation];}- (void)setProgress:(CGFloat)value {    if (_progress != value) {        // Progress values go from 0.0 to 1.0        _progress = MIN(1.0, fabs(value));        [self setNeedsLayout];    }}- (void)layoutSubviews {    // Resize our mask layer based on the current progress    CGRect maskRect = [_maskLayer frame];    maskRect.size.width = CGRectGetWidth([self bounds]) * _progress;    [_maskLayer setFrame:maskRect];}@end

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