ios - 在iOS上模仿截图flash动画

Question

我正在寻找一种复制“闪烁”动画的方法，即在按下 home+lock 时播放。

有谁知道这个动画是否以某种方式可用？

Answer 1

在 iOS 设备上，当您按下 home + lock 并且屏幕闪烁白色时，您会截取屏幕截图。你是说这个效果吗？如果是这样，试试这个：

将UIView具有白色背景颜色的 a 添加到您的视图层次结构中，使其覆盖整个屏幕。然后，启动一个动画，将该视图的不透明度淡化为零。完成后，从其父视图中删除视图：

[UIView animateWithDuration: 0.5 
                 animations: ^{
                               whiteView.alpha = 0.0;
                             }
                 completion: ^(BOOL finished) {
                               [whiteView removeFromSuperview];
                             }
];

Answer 2

尝试：

[UIView animateWithDuration:1 animations:^{
    self.view.backgroundColor = [UIColor blackColor];
    for (UIView *view2 in self.view.subviews) {
        view2.backgroundColor = [UIColor blackColor];
    }
}];
[UIView animateWithDuration:1 animations:^{
    self.view.backgroundColor = [UIColor whiteColor];
    for (UIView *view2 in self.view.subviews) {
        view2.backgroundColor = [UIColor whiteColor];
    }
}];

Answer 3

这些例子给了我灵感，但并没有给我想要的效果。这是我的尝试，看起来非常接近真实交易。

func mimicScreenShotFlash() {

    let aView = UIView(frame: self.view.frame)
    aView.backgroundColor = UIColor.whiteColor()
    self.view.addSubview(aView)

    UIView.animateWithDuration(1.3, delay: 0, options: UIViewAnimationOptions.CurveEaseInOut, animations: { () -> Void in
        aView.alpha = 0.0
        }, completion: { (done) -> Void in
            aView.removeFromSuperview()
    })
}

Answer 4

我找到了一种非常简单的方法来完全模仿 Apple 使用的 Screenshot Flash。我希望每个人都至少尝试一次。

UIView * flashView = [[UIView alloc] initWithFrame:self.view.frame];
flashView.backgroundColor = [UIColor whiteColor];
[self.view addSubview:flashView];

[UIView animateWithDuration:1 delay:0.3 options:0 animations:^{
      flashView.alpha = 0;
    } completion:^(BOOL finished)
     {
        [flashView removeFromSuperview]; 
     }];
}

Answer 5

当前解决方案的两个问题：

1. 将视图放在其他视图上可以（根据我对 UICollectionView 和其他废话的经验）触发自动布局。自动布局很糟糕。Autolayout 使机器做了大量的工作，除了烧 CPU 和电池之外，除了无缘无故地计算之外，还会产生副作用。所以，你不想给它自动布局的理由，例如，将一个子视图添加到一个真正非常关心保持自身布局良好的视图中。

2. 你的视图不一定覆盖整个屏幕，所以如果你想闪烁整个屏幕，你最好使用 UIWindow ...这应该与任何对添加子视图敏感的视图控制器绝缘

这是我的实现，UIView 上的一个类别。我已经包含了在闪烁窗口之前截取屏幕截图的方法，然后将其保存到相机胶卷中。请注意，UIWindow 在添加时似乎想要做自己的动画，它通常会在三分之一秒内淡入。可能有更好的方法告诉它不要这样做。

// stupid blocks
typedef void (^QCompletion)(BOOL complete);

@interface UIView (QViewAnimation)
+ (UIImage *)screenshot; // whole screen 
+ (void)flashScreen:(QCompletion)complete;
- (UIImage *)snapshot; // this view only
- (void)takeScreenshotAndFlashScreen;
@end

@implementation UIView (QViewAnimation)

+ (UIImage *)screenshot;
{

    NSArray *windows = [[UIApplication sharedApplication] windows];
    UIWindow *window = nil;
    if (windows.count) {
        window = windows[0];
        return [window snapshot];
    } else {
        NSLog(@"Screenshot failed.");
        return nil;
    }
}

- (UIImage *)snapshot;
{
    UIGraphicsBeginImageContextWithOptions(self.bounds.size, YES, 0);
    [self drawViewHierarchyInRect:self.bounds afterScreenUpdates:YES];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

+ (void)flashScreen:(QCompletion)complete;
{
    UIScreen *screen = [UIScreen mainScreen];
    CGRect bounds = screen.bounds;
    UIWindow * flash = [[UIWindow alloc] initWithFrame:bounds];
    flash.alpha = 1;
    flash.backgroundColor = [UIColor whiteColor];

    [UIView setAnimationsEnabled:NO];
    [flash makeKeyAndVisible];
    [UIView setAnimationsEnabled:YES];

    [UIView animateWithDuration:0.3
                          delay:0
                        options:UIViewAnimationCurveEaseOut
                     animations:^{
            flash.alpha = 0;
        }
                         completion: ^(BOOL finished)
        {
            flash.hidden = YES;
            [flash autorelease];
            if (complete) {
                complete(YES);
            }

        }];
}

- (void)takeScreenshotAndFlashScreen;
{
    UIImage *image = [UIView screenshot];
    [UIView flashScreen:^(BOOL complete){
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND,0),
                       ^{
            UIImageWriteToSavedPhotosAlbum(image,self,@selector(imageDidFinishSaving:withError:context:),nil);
        });
    }];
}

- (void)imageDidFinishSaving:(UIImage *)image
                   withError:(NSError *)error
                     context:(void *)context;
{
    dispatch_async(dispatch_get_main_queue(),^{
        // send an alert that the image saved
    });
}

@end