Objective-c 动画与尾随约束的约束不稳定问题

Question

我正在使用 Objective-c 开发一个 IOS 应用程序。在为视图的约束设置动画时，我遇到了一个不稳定的问题。动画在帧的最终位置上效果很好，但是随机地，第一个动画块省略了尾随（右）约束（左约束永远不会达到 -20 常量值），但是前导（​​左）、顶部和底部约束正在按预期工作。

请看我上传的视频。在第一次点击中，动画按预期工作，但在第二次点击中出现问题。请指教。

Video showing the problem

- (void)animateTransition:(nonnull id<UIViewControllerContextTransitioning>)transitionContext {
// 1
UIView *containerView = transitionContext.containerView;
UIViewController* toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];

// 2
[containerView addSubview:toViewController.view];

if([toViewController isKindOfClass:[ImageViewController class]]){
    ImageViewController *vcImage = (ImageViewController*)toViewController;
    vcImage.constraintLeft.constant = 20;
    vcImage.constraintTop.constant = self.selectedCardFrame.origin.y + 60.0;
    vcImage.constraintRight.constant = 20.0;
    vcImage.constraintBottom.constant = 0;//self.CollectionView.bounds.size.height - (self.selectedCardFrame.origin.y + self.selectedCardFrame.size.height);
    [toViewController.view layoutIfNeeded];

    NSTimeInterval duration = [self transitionDuration:transitionContext];
    [toViewController.view layoutIfNeeded];
    [UIView animateWithDuration:duration animations:^{
        //First animation block
        vcImage.constraintRight.constant = -20.0;
        vcImage.constraintLeft.constant = -20.0;
        vcImage.constraintTop.constant = -20.0;
        vcImage.constraintBottom.constant = 0;
        [toViewController.view layoutIfNeeded];
        //toViewController.configureRoundedCorners(shouldRound: false)
    } completion:^(BOOL finished) {
        //Second animation block
        [UIView animateWithDuration:duration animations:^{
            vcImage.constraintLeft.constant = 0;
            vcImage.constraintTop.constant = 0.0;
            vcImage.constraintRight.constant = 0;
            vcImage.constraintBottom.constant = 0;
            [toViewController.view layoutIfNeeded];
            //toViewController.configureRoundedCorners(shouldRound: false)
        } completion:^(BOOL finished) {
            [transitionContext completeTransition:finished];
        }];
    }];
}

}

@Sh_Khan 发表评论后更新代码。

- (void)animateTransition:(nonnull id<UIViewControllerContextTransitioning>)transitionContext {
// 1
UIView *containerView = transitionContext.containerView;
UIViewController* toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];

// 2
[containerView addSubview:toViewController.view];
if([toViewController isKindOfClass:[ImageViewController class]]){
    ImageViewController *vcImage = (ImageViewController*)toViewController;
    NSTimeInterval duration = [self transitionDuration:transitionContext];

    [UIView animateWithDuration:0 animations:^{
        vcImage.constraintLeft.constant = 20;
        vcImage.constraintTop.constant = self.selectedCardFrame.origin.y + 60.0;
        vcImage.constraintRight.constant = 20.0;
        vcImage.constraintBottom.constant = 0;

        [toViewController.view layoutIfNeeded];
    } completion:^(BOOL finished) {
        [UIView animateWithDuration:duration animations:^{
            //First animation block
            vcImage.constraintRight.constant = -20.0;
            vcImage.constraintLeft.constant = -20.0;
            vcImage.constraintTop.constant = -20.0;
            vcImage.constraintBottom.constant = 0;
            [toViewController.view layoutIfNeeded];
            //toViewController.configureRoundedCorners(shouldRound: false)
        } completion:^(BOOL finished) {
            //Second animation block
            [UIView animateWithDuration:duration animations:^{
                vcImage.constraintLeft.constant = 0;
                vcImage.constraintTop.constant = 0.0;
                vcImage.constraintRight.constant = 0;
                vcImage.constraintBottom.constant = 0;
                [toViewController.view layoutIfNeeded];
                //toViewController.configureRoundedCorners(shouldRound: false)
            } completion:^(BOOL finished) {
                [transitionContext completeTransition:finished];
            }];
        }];
    }];
}

}

Answer 1

在设置您的 imageView 之前，请尝试重新定位照片。有些东西告诉我图像视图很难确定图像的方向。我曾经在过渡期间发生过这种情况，并会解释为什么您只在某些时候看到这种行为。我对 Objective C 有点生疏，但在设置 imageView 图像之前先试一试并使用它。

-(UIImage*)normalizeImage:(UIImage*)currentImage {
    if (currentImage.imageOrientation == UIImageOrientationUp){
        return currentImage;
    }

    UIGraphicsBeginImageContextWithOptions(currentImage.size, NO, currentImage.scale);
    [currentImage drawInRect:CGRectMake(0, 0, currentImage.size.width, currentImage.size.height)];
    UIImage *_newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return _newImage;
}