Well, the problem is seams that iOS6 UIProgressView and iOS7 UIProgressView have different internal subviews structure. iOS6 progress view is a single view without child view (or some minor view), iOS7 progress view have few additional subview for drawing progress bar and background.
If you remove all subview of UIProgressView on iOS7 than you drawRect: method will work the same as before on iOS6, but you will be totally responsible about drawing your progress view content including progress bar and background.
- (id) initWithCoder: (NSCoder*)aDecoder
{
if(self=[super initWithCoder: aDecoder])
{
// Also you can setup height of your progress here
// self.frame = CGRectMake(0,0,100,yourHeight);
NSArray *subViews = self.subviews;
for(UIView *view in subViews)
{
[view removeFromSuperview];
}
}
return self;
}