title: I add a UIGestureReconizer to a view to detect Touch Down action, but then the buttons above the view won't work anymore
body: <p>I have a view which needs to detect "Touch Down" action on the full view, after I found out normal UITapGestureRecognizer can't accomplish it, I customize UIestureRecognizer class to achieve it, <a href="https://stackoverflow.com/a/15629234/1848847">using this</a>.</p>
  
  <p>So it does work, but I have several buttons on the view, after I can detect the Touch Down action for the view, those buttons stop to work.
  I need both of them to work, the view to detect Touch Down and the buttons can be pressed above the view. How can I achieve it?</p>
  
  <p>To be clear, those buttons just need to detect normal Touch Up Inside action, only the view need to detect Touch Down action. Also, when touch events happen on the buttons, the view doesn't need to do react to the touch event.</p>
  
  <p>Thanks. </p>
  
  <pre class="lang-swift prettyprint-override"><code>import UIKit
  import UIKit.UIGestureRecognizerSubclass
  
  class ViewController: UIViewController {
  
      override func viewDidLoad() {
          super.viewDidLoad()
  
          let t = SingleTouchDownGestureRecognizer(target: self, action: #selector(handleTap(sender:)))
          self.view.addGestureRecognizer(t)
  
      }
  
      @objc func handleTap(sender: UITapGestureRecognizer? = nil) {
  
          self.view.backgroundColor = #colorLiteral(red: 0.2392156869, green: 0.6745098233, blue: 0.9686274529, alpha: 1)
          UIView.animate(withDuration: 1) {
              self.view.backgroundColor = #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1)
          }
  
      }
      @IBAction func testBtnPressed(_ sender: Any) {
          print("testBtnPressed!")
      }
  
  }
  
  class SingleTouchDownGestureRecognizer: UIGestureRecognizer {
      override func touchesBegan(_ touches: Set&lt;UITouch&gt;, with event: UIEvent) {
          if self.state == .possible {
              self.state = .recognized
          }
      }
      override func touchesMoved(_ touches: Set&lt;UITouch&gt;, with event: UIEvent) {
          self.state = .failed
      }
      override func touchesEnded(_ touches: Set&lt;UITouch&gt;, with event: UIEvent) {
          self.state = .failed
      }
  }
  </code></pre>