home: reduce viewpager sensitivity

By default, ViewPager2's sensitivity can result in vertical scroll
actions being registered as horizontal scroll actions, which is bad
for UX. Fix that by reflecting into the internal RecyclerView and
changing the touch slope value.

app/src/main/java/org/oxycblt/auxio/home/HomeFragment.kt

@@ -78,7 +78,32 @@ class HomeFragment : Fragment() {
             true
         }
 
-        binding.homePager.adapter = HomePagerAdapter()
+        binding.homePager.apply {
+            adapter = HomePagerAdapter()
+
+            // By default, ViewPager2's sensitivity is high enough to result in vertical
+            // scroll events being registered as horizontal scroll events. Reflect into the
+            // internal recyclerview and  change the touch slope so that touch actions will
+            // act more as a scroll than as a swipe.
+            // Derived from: https://al-e-shevelev.medium.com/how-to-reduce-scroll-sensitivity-of-viewpager2-widget-87797ad02414
+
+            try {
+                val recycler = ViewPager2::class.java.getDeclaredField("mRecyclerView").apply {
+                    isAccessible = true
+                    get(binding.homePager)
+                }
+
+                RecyclerView::class.java.getDeclaredField("mTouchSlop").apply {
+                    isAccessible = true
+
+                    val slop = get(recycler) as Int
+                    set(recycler, slop * 8)
+                }
+            } catch (e: Exception) {
+                logE("Unable to reduce ViewPager sensitivity")
+                logE(e.stackTraceToString())
+            }
+        }
 
         TabLayoutMediator(binding.homeTabs, binding.homePager) { tab, pos ->
             val labelRes = when (pos) {