From f52091dff5f2c6b67c6f7102dfa3371ef046f517 Mon Sep 17 00:00:00 2001
From: mertsimsek <mertsimsek1992@gmail.com>
Date: Tue, 3 Mar 2020 14:00:32 +0300
Subject: [PATCH] Add attach() and detach() methods.

---
 .../iammert/tabscrollattacher/MainActivity.kt |   7 +-
 .../tabscrollattacherlib/TabScrollAttacher.kt | 109 ++++++++++--------
 2 files changed, 66 insertions(+), 50 deletions(-)

diff --git a/app/src/main/java/com/iammert/tabscrollattacher/MainActivity.kt b/app/src/main/java/com/iammert/tabscrollattacher/MainActivity.kt
index 6393ac0..3c8a404 100644
--- a/app/src/main/java/com/iammert/tabscrollattacher/MainActivity.kt
+++ b/app/src/main/java/com/iammert/tabscrollattacher/MainActivity.kt
@@ -33,9 +33,14 @@ class MainActivity : AppCompatActivity() {
          * SETUP ATTACHER
          */
         val indexOffsets = getCategoryIndexOffsets(categories)
-        TabScrollAttacher(tabLayout, recyclerView, indexOffsets) {
+        val attacher = TabScrollAttacher(tabLayout, recyclerView, indexOffsets) {
             scrollSmoothly()
         }
+
+        attacher.attach()
+
+        //attacher.detach()
+
     }
 
     /**
diff --git a/tabscrollattacherlib/src/main/java/com/iammert/tabscrollattacherlib/TabScrollAttacher.kt b/tabscrollattacherlib/src/main/java/com/iammert/tabscrollattacherlib/TabScrollAttacher.kt
index 9f4e167..3e9d247 100644
--- a/tabscrollattacherlib/src/main/java/com/iammert/tabscrollattacherlib/TabScrollAttacher.kt
+++ b/tabscrollattacherlib/src/main/java/com/iammert/tabscrollattacherlib/TabScrollAttacher.kt
@@ -13,67 +13,78 @@ class TabScrollAttacher(
     configuration: Configuration.() -> Unit = {}
 ) {
 
-    private val layoutManager: LinearLayoutManager
+    private lateinit var layoutManager: LinearLayoutManager
+
+    private lateinit var config: Configuration
 
     private var attacherState = AttacherState.IDLE
 
-    private val config: Configuration
+    private var isAttached = false
+
+    private var scrollListener = object : RecyclerView.OnScrollListener() {
+        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
+            super.onScrolled(recyclerView, dx, dy)
+
+            if (attacherState == AttacherState.TAB_SELECTED) {
+                return
+            }
+
+            val isScrolling = dx != 0 || dy != 0
+            if (attacherState == AttacherState.IDLE && isScrolling) {
+                attacherState = AttacherState.RECYCLERVIEW_SCROLLING
+            }
+
+            val calculatedRecyclerViewItemPosition = when {
+                layoutManager.findLastVisibleItemPosition() == layoutManager.itemCount - 1 -> layoutManager.findLastVisibleItemPosition()
+                layoutManager.findFirstVisibleItemPosition() == 0 -> layoutManager.findFirstVisibleItemPosition()
+                else -> findMidVisibleRecyclerItemPosition()
+            }
+
+            val tabIndex = getTabIndex(calculatedRecyclerViewItemPosition)
+            if (tabIndex != tabLayout.selectedTabPosition) {
+                tabLayout.getTabAt(tabIndex)?.select()
+            }
+        }
+
+        override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
+            super.onScrollStateChanged(recyclerView, newState)
+            if (newState == RecyclerView.SCROLL_STATE_IDLE) {
+                attacherState = AttacherState.IDLE
+            }
+        }
+    }
+
+    private var tabSelectedListener = object : SimpleTabSelectedListener() {
+        override fun onTabSelected(p0: TabLayout.Tab?) {
+            super.onTabSelected(p0)
+            if (attacherState != AttacherState.RECYCLERVIEW_SCROLLING) {
+                attacherState = AttacherState.TAB_SELECTED
+                val recyclerViewPosition = tabStartIndexOffsets[tabLayout.selectedTabPosition]
+                recyclerView.scrollToPosition(recyclerViewPosition, config.scrollMethod)
+            }
+        }
+    }
 
     init {
         require(recyclerView.layoutManager is LinearLayoutManager) { "Only LinearLayoutManager is supported." }
         layoutManager = recyclerView.layoutManager as LinearLayoutManager
         config = Configuration().apply(configuration)
-        observeRecyclerViewScroll()
-        observeTabLayoutSelection()
     }
 
-    private fun observeRecyclerViewScroll() {
-        recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
-            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
-                super.onScrolled(recyclerView, dx, dy)
-
-                if (attacherState == AttacherState.TAB_SELECTED) {
-                    return
-                }
-
-                val isScrolling = dx != 0 || dy != 0
-                if (attacherState == AttacherState.IDLE && isScrolling) {
-                    attacherState = AttacherState.RECYCLERVIEW_SCROLLING
-                }
-
-                val calculatedRecyclerViewItemPosition = when {
-                    layoutManager.findLastVisibleItemPosition() == layoutManager.itemCount - 1 -> layoutManager.findLastVisibleItemPosition()
-                    layoutManager.findFirstVisibleItemPosition() == 0 -> layoutManager.findFirstVisibleItemPosition()
-                    else -> findMidVisibleRecyclerItemPosition()
-                }
-
-                val tabIndex = getTabIndex(calculatedRecyclerViewItemPosition)
-                if (tabIndex != tabLayout.selectedTabPosition) {
-                    tabLayout.getTabAt(tabIndex)?.select()
-                }
-            }
-
-            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
-                super.onScrollStateChanged(recyclerView, newState)
-                if (newState == RecyclerView.SCROLL_STATE_IDLE) {
-                    attacherState = AttacherState.IDLE
-                }
-            }
-        })
+    fun detach() {
+        if (isAttached) {
+            recyclerView.removeOnScrollListener(scrollListener)
+            tabLayout.removeOnTabSelectedListener(tabSelectedListener)
+            isAttached = false
+        }
     }
 
-    @SuppressLint("ClickableViewAccessibility")
-    private fun observeTabLayoutSelection() {
-        tabLayout.addOnTabSelectedListener(object : SimpleTabSelectedListener() {
-            override fun onTabSelected(p0: TabLayout.Tab?) {
-                super.onTabSelected(p0)
-                if (attacherState != AttacherState.RECYCLERVIEW_SCROLLING) {
-                    attacherState = AttacherState.TAB_SELECTED
-                    val recyclerViewPosition = tabStartIndexOffsets[tabLayout.selectedTabPosition]
-                    recyclerView.scrollToPosition(recyclerViewPosition, config.scrollMethod)
-                }
-            }
-        })
+    fun attach() {
+        if (isAttached.not()) {
+            recyclerView.addOnScrollListener(scrollListener)
+            tabLayout.addOnTabSelectedListener(tabSelectedListener)
+            isAttached = true
+        }
     }
 
     private fun findMidVisibleRecyclerItemPosition(): Int {