Make it harder to accidentally dismiss image preview.

The swipe downwards now only triggers when lifting the finger, after having swiped far enough, and then only if the finger is lifted soon after it was initially pressed.
Awful · Oct 21, 2014 · 043f3e8 · 043f3e8
1 parent 74f759d
commit 043f3e8
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Showing 2 changed files with 41 additions and 9 deletions.
diff --git a/Source/Images/ImageViewController.swift b/Source/Images/ImageViewController.swift
@@ -6,6 +6,7 @@ import UIKit
 
 /// Downloads an image and shows it in a zoomable scroll view for inspection and further action.
 class ImageViewController: AwfulViewController {
+
     let URL: NSURL!
     var doneAction: (() -> Void)?
     private var downloadTask: NSURLSessionTask!
@@ -17,10 +18,10 @@ class ImageViewController: AwfulViewController {
     @IBOutlet private weak var activityIndicator: UIActivityIndicatorView!
     @IBOutlet private weak var scrollView: UIScrollView!
     @IBOutlet private weak var imageView: FLAnimatedImageView!
-    @IBOutlet private var swipeGestureRecognizer: UISwipeGestureRecognizer!
     @IBOutlet private var overlaidViews: [UIView]!
     @IBOutlet private weak var actionButton: UIButton!
     @IBOutlet private weak var statusBarBackgroundViewHeightConstraint: NSLayoutConstraint!
+    @IBOutlet var panToDismissGestureRecognizer: UIPanGestureRecognizer!
 
     init(URL: NSURL) {
         self.URL = URL
@@ -33,7 +34,6 @@ class ImageViewController: AwfulViewController {
 
     override func viewDidLoad() {
         super.viewDidLoad()
-        scrollView.panGestureRecognizer.requireGestureRecognizerToFail(swipeGestureRecognizer)
         fetchImage()
     }
 
@@ -158,8 +158,30 @@ class ImageViewController: AwfulViewController {
         dismiss()
     }
 
-    @IBAction func didSwipeDown(sender: UISwipeGestureRecognizer) {
-        dismiss()
+    private var panStart: NSTimeInterval!
+
+    @IBAction func didPanToDismiss(sender: UIPanGestureRecognizer) {
+        switch sender.state {
+        case .Began:
+            panStart = NSProcessInfo.processInfo().systemUptime
+        case .Changed:
+            let velocity = sender.velocityInView(view)
+            if velocity.y < 0 || abs(velocity.x) > abs(velocity.y) {
+                sender.enabled = false
+                sender.enabled = true
+            }
+        case .Ended:
+            let translation = sender.translationInView(view)
+            if abs(translation.x) < 30 {
+                if translation.y > 60 {
+                    if NSProcessInfo.processInfo().systemUptime - panStart < 0.5 {
+                        dismiss()
+                    }
+                }
+            }
+        default:
+            break;
+        }
     }
 
     private func setShowingOverlaidViews(showing: Bool, animated: Bool) {
@@ -209,6 +231,16 @@ class ImageViewController: AwfulViewController {
     }
 }
 
+extension ImageViewController: UIGestureRecognizerDelegate {
+
+    func gestureRecognizer(gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWithGestureRecognizer otherGestureRecognizer: UIGestureRecognizer) -> Bool {
+        if gestureRecognizer == panToDismissGestureRecognizer {
+            return true
+        }
+        fatalError("unexpected gesture recognizer")
+    }
+}
+
 class ContentCenteringScrollView: UIScrollView {
     override func layoutSubviews() {
         super.layoutSubviews()

diff --git a/Source/Images/ImageViewController.xib b/Source/Images/ImageViewController.xib
@@ -9,9 +9,9 @@
                 <outlet property="actionButton" destination="1rR-c0-50m" id="6Yj-zG-QCB"/>
                 <outlet property="activityIndicator" destination="IJO-hy-jmY" id="ngd-Vo-Qfu"/>
                 <outlet property="imageView" destination="l6V-lC-TXd" id="KE4-5k-v2Q"/>
+                <outlet property="panToDismissGestureRecognizer" destination="6MC-Po-de8" id="juE-9E-ros"/>
                 <outlet property="scrollView" destination="ZLh-kG-l6m" id="tZs-7X-gYN"/>
                 <outlet property="statusBarBackgroundViewHeightConstraint" destination="oaK-Qa-JlQ" id="0o7-7T-UjP"/>
-                <outlet property="swipeGestureRecognizer" destination="w93-BF-zAY" id="uIJ-FG-UpT"/>
                 <outlet property="view" destination="i5M-Pr-FkT" id="sfx-zR-JGt"/>
                 <outletCollection property="overlaidViews" destination="5rZ-lk-hWQ" collectionClass="NSMutableArray" id="iIB-1I-Gc3"/>
                 <outletCollection property="overlaidViews" destination="1rR-c0-50m" collectionClass="NSMutableArray" id="DCy-UM-8xx"/>
@@ -106,20 +106,20 @@
                 <constraint firstItem="ZLh-kG-l6m" firstAttribute="bottom" secondItem="i5M-Pr-FkT" secondAttribute="bottom" id="rXK-ap-Kk7"/>
             </constraints>
             <connections>
-                <outletCollection property="gestureRecognizers" destination="w93-BF-zAY" appends="YES" id="Siy-5S-xww"/>
                 <outletCollection property="gestureRecognizers" destination="eQi-oZ-TBD" appends="YES" id="viY-NT-RgM"/>
+                <outletCollection property="gestureRecognizers" destination="6MC-Po-de8" appends="YES" id="IwH-8y-qJd"/>
             </connections>
         </view>
         <tapGestureRecognizer id="eQi-oZ-TBD">
             <connections>
                 <action selector="didTapImage:" destination="-1" id="YdM-RZ-VTa"/>
             </connections>
         </tapGestureRecognizer>
-        <swipeGestureRecognizer direction="down" id="w93-BF-zAY">
+        <panGestureRecognizer minimumNumberOfTouches="1" id="6MC-Po-de8" userLabel="Swipe to Dismiss Gesture Recognizer">
             <connections>
-                <action selector="didSwipeDown:" destination="-1" id="ksH-Ez-MuY"/>
+                <action selector="didPanToDismiss:" destination="-1" id="dZy-7V-LEZ"/>
             </connections>
-        </swipeGestureRecognizer>
+        </panGestureRecognizer>
     </objects>
     <resources>
         <image name="action" width="19" height="26"/>