Add Grid auto-column example

Author: Luceefer

app/build.gradle

@@ -21,6 +21,6 @@ android {
 
 dependencies {
     compile fileTree(dir: 'libs', include: ['*.jar'])
-    compile 'com.android.support:design:23.0.1'
-    compile 'com.android.support:recyclerview-v7:23.0.1'
+    compile 'com.android.support:design:23.1.1'
+    compile 'com.android.support:recyclerview-v7:23.1.1'
 }

app/src/main/java/com/codentrick/recyclerviewcollection/ui/GridActivity.java

@@ -1,8 +1,10 @@
 package com.codentrick.recyclerviewcollection.ui;
 
+import android.content.Context;
 import android.os.Bundle;
 import android.support.v7.widget.GridLayoutManager;
 import android.support.v7.widget.RecyclerView;
+import android.util.TypedValue;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.TextView;
@@ -21,8 +23,9 @@ public class GridActivity extends RecyclerViewActivity {
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_simple);
+        GridAutofitLayoutManager layoutManager = new GridAutofitLayoutManager(this, 160);
         RecyclerView mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
-        mRecyclerView.setLayoutManager(new GridLayoutManager(this, 3));
+        mRecyclerView.setLayoutManager(layoutManager);
         mRecyclerView.setAdapter(new SimpleAdapter());
     }
 
@@ -54,4 +57,55 @@ public void onBindViewHolder(SimpleHolder simpleHolder, int i) {
             simpleHolder.mTextView.setText(DataProvider.JAVA_BOOKS[i]);
         }
     }
+
+    public static class GridAutofitLayoutManager extends GridLayoutManager {
+
+        private int mColumnWidth;
+        private boolean mColumnWidthChanged = true;
+
+        public GridAutofitLayoutManager(Context context, int columnWidth) {
+            super(context, 1);
+            setColumnWidth(checkedColumnWidth(context, columnWidth));
+        }
+
+        public GridAutofitLayoutManager(Context context, int columnWidth, int orientation, boolean reverseLayout) {
+        /* Initially set spanCount to 1, will be changed automatically later. */
+            super(context, 1, orientation, reverseLayout);
+            setColumnWidth(checkedColumnWidth(context, columnWidth));
+        }
+
+        private int checkedColumnWidth(Context context, int columnWidth) {
+            if (columnWidth <= 0) {
+            /* Set default columnWidth value (48dp here). It is better to move this constant
+            to static constant on top, but we need context to convert it to dp, so can't really
+            do so. */
+                columnWidth = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 48,
+                        context.getResources().getDisplayMetrics());
+            }
+            return columnWidth;
+        }
+
+        public void setColumnWidth(int newColumnWidth) {
+            if (newColumnWidth > 0 && newColumnWidth != mColumnWidth) {
+                mColumnWidth = newColumnWidth;
+                mColumnWidthChanged = true;
+            }
+        }
+
+        @Override
+        public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
+            if (mColumnWidthChanged && mColumnWidth > 0) {
+                int totalSpace;
+                if (getOrientation() == VERTICAL) {
+                    totalSpace = getWidth() - getPaddingRight() - getPaddingLeft();
+                } else {
+                    totalSpace = getHeight() - getPaddingTop() - getPaddingBottom();
+                }
+                int spanCount = Math.max(1, totalSpace / mColumnWidth);
+                setSpanCount(spanCount);
+                mColumnWidthChanged = false;
+            }
+            super.onLayoutChildren(recycler, state);
+        }
+    }
 }