Add support to GridLayoutManager

Author: rubensousa

build.gradle

@@ -3,7 +3,7 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.3.0'
+        classpath 'com.android.tools.build:gradle:2.3.3'
         classpath 'com.jfrog.bintray.gradle:gradle-bintray-plugin:1.7'
     }
 }

gravitysnaphelper/src/main/java/com/github/rubensousa/gravitysnaphelper/GravityDelegate.java

@@ -3,6 +3,7 @@
 
 import android.os.Build;
 import android.support.annotation.NonNull;
+import android.support.v7.widget.GridLayoutManager;
 import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.OrientationHelper;
 import android.support.v7.widget.RecyclerView;
@@ -150,6 +151,11 @@ private View findStartView(RecyclerView.LayoutManager layoutManager,
 
         if (layoutManager instanceof LinearLayoutManager) {
             int firstChild = ((LinearLayoutManager) layoutManager).findFirstVisibleItemPosition();
+            int offset = 1;
+
+            if (layoutManager instanceof GridLayoutManager) {
+                offset += ((GridLayoutManager) layoutManager).getSpanCount() - 1;
+            }
 
             if (firstChild == RecyclerView.NO_POSITION) {
                 return null;
@@ -174,7 +180,7 @@ private View findStartView(RecyclerView.LayoutManager layoutManager,
             // to avoid having the last item not completely visible.
             boolean endOfList = ((LinearLayoutManager) layoutManager)
                     .findLastCompletelyVisibleItemPosition()
-                    == layoutManager.getItemCount() - 1;
+                    >= layoutManager.getItemCount() - offset;
 
             if (visibleWidth > 0.5f && !endOfList) {
                 return child;
@@ -185,7 +191,7 @@ private View findStartView(RecyclerView.LayoutManager layoutManager,
             } else {
                 // If the child wasn't returned, we need to return
                 // the next view close to the start.
-                return layoutManager.findViewByPosition(firstChild + 1);
+                return layoutManager.findViewByPosition(firstChild + offset);
             }
         }
 
@@ -197,6 +203,11 @@ private View findEndView(RecyclerView.LayoutManager layoutManager,
 
         if (layoutManager instanceof LinearLayoutManager) {
             int lastChild = ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();
+            int offset = 1;
+
+            if (layoutManager instanceof GridLayoutManager) {
+                offset += ((GridLayoutManager) layoutManager).getSpanCount() - 1;
+            }
 
             if (lastChild == RecyclerView.NO_POSITION) {
                 return null;
@@ -217,7 +228,7 @@ private View findEndView(RecyclerView.LayoutManager layoutManager,
             // If we're at the start of the list, we shouldn't snap
             // to avoid having the first item not completely visible.
             boolean startOfList = ((LinearLayoutManager) layoutManager)
-                    .findFirstCompletelyVisibleItemPosition() == 0;
+                    .findFirstCompletelyVisibleItemPosition() <= offset - 1;
 
             if (visibleWidth > 0.5f && !startOfList) {
                 return child;
@@ -227,7 +238,7 @@ private View findEndView(RecyclerView.LayoutManager layoutManager,
                 return null;
             } else {
                 // If the child wasn't returned, we need to return the previous view
-                return layoutManager.findViewByPosition(lastChild - 1);
+                return layoutManager.findViewByPosition(lastChild - offset);
             }
         }
         return null;

gravitysnaphelper/src/main/java/com/github/rubensousa/gravitysnaphelper/GravityPagerSnapHelper.java

@@ -3,6 +3,8 @@
 
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
+import android.support.v7.widget.GridLayoutManager;
+import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.PagerSnapHelper;
 import android.support.v7.widget.RecyclerView;
 import android.view.View;
@@ -27,6 +29,11 @@ public GravityPagerSnapHelper(int gravity, boolean enableSnapLastItem,
     @Override
     public void attachToRecyclerView(@Nullable RecyclerView recyclerView)
             throws IllegalStateException {
+        if (!(recyclerView.getLayoutManager() instanceof LinearLayoutManager)
+                || recyclerView.getLayoutManager() instanceof GridLayoutManager) {
+            throw new IllegalStateException("GravityPagerSnapHelper needs a RecyclerView" +
+                    " with a LinearLayoutManager");
+        }
         delegate.attachToRecyclerView(recyclerView);
         super.attachToRecyclerView(recyclerView);
     }

gravitysnaphelper/src/main/java/com/github/rubensousa/gravitysnaphelper/GravitySnapHelper.java

@@ -19,11 +19,8 @@
 
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
-import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.LinearSnapHelper;
-import android.support.v7.widget.OrientationHelper;
 import android.support.v7.widget.RecyclerView;
-import android.view.Gravity;
 import android.view.View;