如何更改CAGradientLayer的颜色像屏幕保护程序？

Question

我创建UIView了应用CAGradientLayer色彩效果,因为我附加了Image Bellow.现在在这里我想要像屏幕保护程序一样平滑地改变它的渐变颜色从上到下.我已经尝试使用NStimer那个位Done但它的颜色变化CAGradientLayer看起来像混蛋.

对于上面我使用Bellow方法代码: -

Timer =  [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(TIMER) userInfo:nil repeats:NO];

-(void)TIMER
{
        Count++;
        [view_Color1 removeFromSuperview];

        view_Color1 = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 320, 341)];
        CAGradientLayer *gradient = [CAGradientLayer layer];
        gradient.frame = self.view_Color.bounds;

        if (Count == 1)
        {
            gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor greenColor] CGColor], (id)[[UIColor  colorWithRed:44/255.0 green:255/255.0 blue:255/255.0 alpha:1.0f] CGColor], (id)[[UIColor  colorWithRed:0/255.0 green:0/255.0 blue:254/255.0 alpha:1.0f] CGColor], (id)[[UIColor  colorWithRed:252/255.0 green:0/255.0 blue:255/255.0 alpha:1.0f] CGColor], (id)[[UIColor  colorWithRed:252/255.0 green:0/255.0 blue:6/255.0 alpha:1.0f] CGColor], (id)[[UIColor  colorWithRed:253/255.0 green:131/255.0 blue:6/255.0 alpha:1.0f]CGColor], (id)[[UIColor  colorWithRed:255/255.0 green:237/255.0 blue:10/255.0 alpha:1.0f]CGColor], nil];
        }
        else if (Count == 2)
        {
            gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor  colorWithRed:255/255.0 green:237/255.0 blue:10/255.0 alpha:1.0f]CGColor],(id)[[UIColor greenColor] CGColor], (id)[[UIColor  colorWithRed:44/255.0 green:255/255.0 blue:255/255.0 alpha:1.0f] CGColor], (id)[[UIColor  colorWithRed:0/255.0 green:0/255.0 blue:254/255.0 alpha:1.0f] CGColor], (id)[[UIColor  colorWithRed:252/255.0 green:0/255.0 blue:255/255.0 alpha:1.0f] CGColor], (id)[[UIColor  colorWithRed:252/255.0 green:0/255.0 blue:6/255.0 alpha:1.0f] CGColor], (id)[[UIColor  colorWithRed:253/255.0 green:131/255.0 blue:6/255.0 alpha:1.0f]CGColor],nil];
        }
        //and so on still count is 7 then again its 1 to continue here are count use for chagen 7 color gradient use and repeat.

        [self.view addSubview:view_Color1];
        [self.view_Color1.layer addSublayer:gradient];

        [myappdelegare sharedinstance].str_LastColorClick = [[NSString alloc]initWithFormat:@"MultiColor"];
        Timer =  [NSTimer scheduledTimerWithTimeInterval:0.30 target:self selector:@selector(TIMER) userInfo:nil repeats:NO];

}

你能帮我么？

谢谢

Answer 1

我没有注意到你在每一步都在用颜色"跳跃".

这是一个动画的代码:

- (void) initGradient
{
    if ( !gradient ) {
        gradient = [CAGradientLayer layer];
        gradient.frame = self.view.bounds;
        [self.view.layer addSublayer:gradient];

        NSArray *baseColors = [NSArray arrayWithObjects:(id)[UIColor yellowColor].CGColor, (id)[UIColor redColor].CGColor, (id)[UIColor blueColor].CGColor, (id)[UIColor greenColor].CGColor, nil];
        NSMutableArray *colors = [NSMutableArray arrayWithArray:baseColors];
        [colors addObjectsFromArray:baseColors];
        gradient.colors = colors;

        cnt = [baseColors count];

        NSMutableArray *locations = [NSMutableArray array];
        CGFloat step = 1. / (cnt - 1.);
        CGFloat loc = 0;
        for ( NSUInteger i = 0; i < [colors count]; i++ ) {
            [locations addObject:@(loc)];
            loc += step;
        }
        gradient.locations = [locations copy];
    }
}

-(void)TIMER
{
    NSMutableArray *locations = [NSMutableArray array];
    CGFloat step = 1. / (cnt - 1.);
    static const CGFloat speed = 3;
    CGFloat initialStep = speed / gradient.bounds.size.height;
    CGFloat loc = [gradient.locations[0] floatValue] - initialStep;
    if ( loc <= -1 - step )
        loc = initialStep;
    for ( NSUInteger i = 0; i < [gradient.locations count]; i++ ) {
        [locations addObject:@(loc)];
        loc += step;
    }

    [CATransaction begin];
    [CATransaction setValue:(id)kCFBooleanTrue
                     forKey:kCATransactionDisableActions];
    gradient.locations = [locations copy];
    [CATransaction commit];

    Count++;
    if ( Count >= [gradient.colors count] )
        Count = 0;

    [self performSelector:@selector(TIMER) withObject:nil afterDelay:0.04];
}

它仍有一个小问题,即视图的顶部像素获得混合色,但动画效果很好.您也可以调整速度(静态CGFloat速度).我把它留给你解决 - 也许剪辑.