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in Technique[技术] by (71.8m points)

ios - UIPickerView, detect "rolling wheel" start and stop?

I just discovered that if I do the following:

  1. Click the button that animates a UIPickerView into my view
  2. Quickly start the wheel rolling towards, then past, the last item
  3. Dismiss the view with a button

Then it has not yet selected the last item yet.

I tried this by simply outputting to the console whenever the didSelectRow method was fired, and it fires when the wheel stabilizes on the last item.

Can I detect that the wheel is still rolling, so that I can delay checking it for a selected value until it stabilizes?

If it matters, I'm programming in MonoTouch, but I can read Objective-C code well enough to reimplement it, if you have a code example that is.

See Question&Answers more detail:os

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by (71.8m points)

As animation keys don't work, I wrote this simple function that works for detecting if a UIPickerView is currently moving.

-(bool) anySubViewScrolling:(UIView*)view
{
    if( [ view isKindOfClass:[ UIScrollView class ] ] )
    {
        UIScrollView* scroll_view = (UIScrollView*) view;
        if( scroll_view.dragging || scroll_view.decelerating )
        {
            return true;
        }
    }

    for( UIView *sub_view in [ view subviews ] )
    {
        if( [ self anySubViewScrolling:sub_view ] )
        {
            return true;
        }
    }

    return false;
}

It ends up returning true five levels deep.


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