Incorrect page change detected when scrolling outside of view

[aaulthudl]

Environment

package	version
react-native-tab-view	3.1.1
react-native-pager-view	5.4.9
react-native	0.64.3
expo	44.0.0
node	12.13.0
npm or yarn	yarn@v1.22.18

Description

Using react-native-tab-view, we have a TabView and a sidebar to the side of it. When you swipe on the TabView and drag it over the sidebar it registers a page switch but it doesn't handle it properly so no page selected event is emitted. The code around this is based in react-native-pager-view.

Also reported in that repo, satya164/react-native-tab-view#1365.

Current behavior

I have a TabView alongside a sidebar. When a swipe is started on the view and is released at edge of the sidebar, the tab index doesn't change (onIndexChange() isn't called) but the tab still changes. This leaves the tabs in an incorrect state and some of the tabs can't be switched to.

Screen.Recording.2022-06-23.at.13.48.40.online-video-cutter.com.mp4

Expected behavior

When a full swipe happens then the tab is changed correctly. Perhaps once the swipe leaves the view then it counts it as swiped, rather than waiting until the swipe is released.

Reproducible Demo

I've forked the react-native-tab-view repo and added the sidebar to the example code.

aaulthudl/react-native-tab-view

Patch Fix

We've added a patch using patch-package to automatically switch pages properly when the swipe leaves the container. It doesn't have a bounce animation when switching pages though.

diff --git a/node_modules/react-native-pager-view/.DS_Store b/node_modules/react-native-pager-view/.DS_Store
new file mode 100644
index 0000000..7083c2c
Binary files /dev/null and b/node_modules/react-native-pager-view/.DS_Store differ
diff --git a/node_modules/react-native-pager-view/ios/.DS_Store b/node_modules/react-native-pager-view/ios/.DS_Store
new file mode 100644
index 0000000..40daf43
Binary files /dev/null and b/node_modules/react-native-pager-view/ios/.DS_Store differ
diff --git a/node_modules/react-native-pager-view/ios/ReactNativePageView.m b/node_modules/react-native-pager-view/ios/ReactNativePageView.m
index 9f8ed5b..8ddad58 100644
--- a/node_modules/react-native-pager-view/ios/ReactNativePageView.m
+++ b/node_modules/react-native-pager-view/ios/ReactNativePageView.m
@@ -476,6 +476,16 @@ - (void)scrollViewDidScroll:(UIScrollView *)scrollView {
         CGFloat contentOffset =[self isHorizontal] ? scrollView.contentOffset.x : scrollView.contentOffset.y;
         CGFloat topBound = [self isHorizontal] ? scrollView.bounds.size.width : scrollView.bounds.size.height;

+        // If a drag goes outside of the content container it should end the drag
+        CGFloat lastContentOffset = [self isHorizontal] ? self.lastContentOffset.x : self.lastContentOffset.y;
+        if (contentOffset <= 0 && lastContentOffset != 0) {
+            scrollView.scrollEnabled = NO;
+            scrollView.scrollEnabled = YES;
+
+            [self goTo:position animated:YES];
+            return;
+        }
+        
         if ((isFirstPage && contentOffset <= topBound) || (isLastPage && contentOffset >= topBound)) {
             CGPoint croppedOffset = [self isHorizontal] ? CGPointMake(topBound, 0) : CGPointMake(0, topBound);
             scrollView.contentOffset = croppedOffset;