Merge branch 'imageNavBar'

Author: wangrui460

WRNavigationBar_swift/WRNavigationBar_swift/WRNavigationBar/WRNavigationBar.swift

@@ -50,6 +50,7 @@ extension UINavigationBar
  // add a image(nil color) to _UIBarBackground make it clear
  setBackgroundImage(UIImage(), for: .default)
  backgroundImageView = UIImageView(frame: CGRect(x: 0, y: 0, width: Int(bounds.width), height: 64))
+ backgroundImageView?.autoresizingMask = .flexibleWidth
  // _UIBarBackground is first subView for navigationBar
  subviews.first?.insertSubview(backgroundImageView ?? UIImageView(), at: 0)
  }
@@ -66,6 +67,7 @@ extension UINavigationBar
  // add a image(nil color) to _UIBarBackground make it clear
  setBackgroundImage(UIImage(), for: .default)
  backgroundView = UIView(frame: CGRect(x: 0, y: 0, width: Int(bounds.width), height: 64))
+ backgroundView?.autoresizingMask = .flexibleWidth
  // _UIBarBackground is first subView for navigationBar
  subviews.first?.insertSubview(backgroundView ?? UIView(), at: 0)
  }