iOS向子视图添加UIGravityBehavior并不总是有效的

Question

我正在以编程方式将UIGravityBehavior添加到子视图中，但并不总是工作。我在主视图中有4个视图，标签为101,102,103,104，如图中所示：

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但出于某种原因，它似乎只适用于标签103和104。这是我的代码：

-(void)viewsGoinDown
{
    NSPredicate *tagPredicate = [NSPredicate predicateWithFormat:@"self.tag >= 100"];
    NSArray *resultArray = [[self.view subviews] filteredArrayUsingPredicate:tagPredicate];
    for (NSUInteger i =0 ; i < resultArray.count; i++)
    {
        NSUInteger sleeping = 2;
        UIView *mySubview = resultArray [i];
        if (i == 0)
        {
            sleeping = 0;

        }

        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

            sleep(sleeping);


            dispatch_async(dispatch_get_main_queue(), ^()
                           {
                               [self moveDownViews:mySubview];

                           });


        });
    }
}

-(void)moveDownViews:(UIView*)myView
{
    self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
    self.gravityBehavior = [[UIGravityBehavior alloc] initWithItems:@[myView]];
    self.gravityBehavior.magnitude = 1;
    [self.animator addBehavior:self.gravityBehavior];

}

我的问题是，为什么只适用于这两个子视图？，我做错了什么？

我非常感谢你的帮助

Answer 1

请查找以下工作代码：

我已经冒昧地改变了一些你可以根据你的口味改变的实现。

-(void)viewsGoinDown
{
    NSPredicate *tagPredicate = [NSPredicate predicateWithFormat:@"self.tag >= 100"];
    NSArray *resultArray = [[self.view subviews] filteredArrayUsingPredicate:tagPredicate];
    NSUInteger sleeping = 0;
    for (NSUInteger i =0 ; i < resultArray.count; i++)
    {

        UIView *mySubview = resultArray [i];
        [self performSelector:@selector(moveDownViews:) withObject:mySubview afterDelay:sleeping];
        sleeping++;
    }

}

-(void)moveDownViews:(UIView *)myView
{
    self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
    self.gravityBehavior = [[UIGravityBehavior alloc] initWithItems:@[myView]];
    self.gravityBehavior.magnitude = 1;
    [self.animator addBehavior:self.gravityBehavior];
}