fixed crash

Author: AndroidDeveloperLB

app/app.iml

@@ -76,17 +76,24 @@
       <sourceFolder url="file://$MODULE_DIR$/src/androidTest/jni" isTestSource="true" />
       <sourceFolder url="file://$MODULE_DIR$/src/androidTest/rs" isTestSource="true" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/assets" />
+      <excludeFolder url="file://$MODULE_DIR$/build/intermediates/classes" />
+      <excludeFolder url="file://$MODULE_DIR$/build/intermediates/debug" />
+      <excludeFolder url="file://$MODULE_DIR$/build/intermediates/dependency-cache" />
+      <excludeFolder url="file://$MODULE_DIR$/build/intermediates/dex" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/exploded-aar/com.android.support/appcompat-v7/23.1.1/jars" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/exploded-aar/com.android.support/design/23.1.1/jars" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/exploded-aar/com.android.support/recyclerview-v7/23.1.1/jars" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/exploded-aar/com.android.support/support-v4/23.1.1/jars" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/incremental" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/manifests" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/mockable-android-23.jar" />
+      <excludeFolder url="file://$MODULE_DIR$/build/intermediates/pre-dexed" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/res" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/rs" />
       <excludeFolder url="file://$MODULE_DIR$/build/intermediates/symbols" />
+      <excludeFolder url="file://$MODULE_DIR$/build/intermediates/tmp" />
       <excludeFolder url="file://$MODULE_DIR$/build/outputs" />
+      <excludeFolder url="file://$MODULE_DIR$/build/tmp" />
     </content>
     <orderEntry type="jdk" jdkName="Android API 23 Platform" jdkType="Android SDK" />
     <orderEntry type="sourceFolder" forTests="false" />

library/src/main/java/com/lb/recyclerview_fast_scroller/RecyclerViewFastScroller.java

@@ -118,12 +118,11 @@ public void setRecyclerView(final RecyclerView recyclerView) {
                 return;
             recyclerView.addOnScrollListener(onScrollListener);
         }
-        if (recyclerView != null) {
-            final ViewTreeObserver viewTreeObserver = recyclerView.getViewTreeObserver();
-            viewTreeObserver.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
+        if (recyclerView != null)
+            recyclerView.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
                 @Override
                 public boolean onPreDraw() {
-                    viewTreeObserver.removeOnPreDrawListener(this);
+                    recyclerView.getViewTreeObserver().removeOnPreDrawListener(this);
                     if (bubble == null || handle.isSelected())
                         return true;
                     final int verticalScrollOffset = recyclerView.computeVerticalScrollOffset();
@@ -133,7 +132,6 @@ public boolean onPreDraw() {
                     return true;
                 }
             });
-        }
     }
 
     @Override