TabbedBottomSheetDialog: Fix scrollable pages (#5173)

app/src/main/java/eu/kanade/tachiyomi/widget/sheet/BottomSheetViewPager.kt

@@ -0,0 +1,54 @@
+package eu.kanade.tachiyomi.widget.sheet
+import android.content.Context
+import android.util.AttributeSet
+import android.view.View
+import androidx.viewpager.widget.ViewPager
+import java.lang.reflect.Field
+
+/**
+ * From https://github.com/kafumi/android-bottomsheet-viewpager
+ */
+class BottomSheetViewPager @JvmOverloads constructor(
+    context: Context,
+    attrs: AttributeSet? = null
+) : ViewPager(context, attrs) {
+
+    private val positionField: Field = LayoutParams::class.java.getDeclaredField("position").also {
+        it.isAccessible = true
+    }
+
+    override fun getChildAt(index: Int): View {
+        val currentView = getCurrentView() ?: return super.getChildAt(index)
+        return if (index == 0) {
+            currentView
+        } else {
+            var view = super.getChildAt(index)
+            if (view == currentView) {
+                view = super.getChildAt(0)
+            }
+            return view
+        }
+    }
+
+    private fun getCurrentView(): View? {
+        for (i in 0 until childCount) {
+            val child = super.getChildAt(i)
+            val lp = child.layoutParams as? LayoutParams
+            if (lp != null) {
+                val position = positionField.getInt(lp)
+                if (!lp.isDecor && currentItem == position) {
+                    return child
+                }
+            }
+        }
+        return null
+    }
+
+    init {
+        addOnPageChangeListener(object : SimpleOnPageChangeListener() {
+            override fun onPageSelected(position: Int) {
+                requestLayout()
+            }
+        })
+    }
+}