动画会增加UIWebView底部的黑色吗？

Question

有一些帖子，其中UIWebView底部为黑色，可以通过两种简单方法解决。

1. Clear Background of UIWebView
2. Set Opaque to NO.

但是，这仅解决了静态UIWebView的问题，该问题没有更改其Frame或Constraints。

就我而言，我有一个UIWebView，这是在Storyboard的ViewController的View上非常简单的拖放。 没有继承。 我将背景设置为透明，并将不透明设置为否。

到目前为止看起来还不错。 但是当我应用动画时，使用Facebook POP库

1. SetOpaque = YES, With Animation is clips the UIWebView's content showing black color.



2. SetOpaque = NO, With Animation is clips the UIWebView's content showing nothing (a View or something comes in front)



-(void) setConstraint {

    _topConstraintValue = self.topConstraint.constant - 200;

    NSLog(@"Value is UP %f " ,_topConstraintValue);

}

- (IBAction)animateUp:(UIButton *)sender {

    [self setConstraint];

    [VSAnimation popChangeConstraintForBasicAnimation:self.topConstraint begin:0.5 newConstant:_topConstraintValue   withDuartion:0.5 isEaseInAnimation:NO withCompletionBlock:nil];

}




-(void) setConstraintDown {

    _topConstraintValue = 0;
    _topConstraintValue = self.topConstraint.constant;

    NSLog(@"Value is Down %f " ,_topConstraintValue);

}


- (IBAction)animateDown:(UIButton *)sender {

    [self setConstraintDown];

    [VSAnimation popChangeConstraintForBasicAnimation:self.topConstraint begin:0.5 newConstant:[self getAnimatableConstraint:_topConstraintValue] withDuartion:0.5 isEaseInAnimation:NO withCompletionBlock:nil];
}


-(float)getAnimatableConstraint:(float)constant{

    return  constant+200.0;
}

-(float)getReverseAnimatableConstraint:(float)constant{

    return  constant-200.0;
}

VS里面的方法如下

//VSAnimation.m

+(void)popChangeConstraintForBasicAnimation:(NSLayoutConstraint *) layoutConstraintToPopChange begin:(float) beginTime newConstant:(CGFloat) newConstant withDuartion:(float)duration isEaseInAnimation:(BOOL)isEaseIn withCompletionBlock:(void (^)(POPAnimation *anim, BOOL finished)) completitionBlock{

    NSString *key = [NSString stringWithFormat:@"constraints_changed_%@", layoutConstraintToPopChange];

    POPBasicAnimation *basicAnim = [layoutConstraintToPopChange pop_animationForKey:key];
    if(basicAnim){
        basicAnim.toValue = @(newConstant);
        basicAnim.completionBlock = completitionBlock;
    }else{

        basicAnim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayoutConstraintConstant];
        if(isEaseIn)
            basicAnim.timingFunction=[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
        else
            basicAnim.timingFunction=[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
        basicAnim.toValue = @(newConstant);
        basicAnim.completionBlock = completitionBlock;
        basicAnim.beginTime = [self timeWithDelay:beginTime];
        basicAnim.delegate = self;
        basicAnim.duration = duration;

        [layoutConstraintToPopChange pop_addAnimation:basicAnim forKey:key];
    }
}

底部的黑线/透明线是什么。 动画UIWebView时如何阻止这种情况增加。

图片：

显示动画向上和动画向下。