Updated Android (markdown)

Android.md

@@ -78,6 +78,8 @@ Use `gomobile bind`, generate an aar file and import this to your Android Studio
 
 ## Implement a class inheriting GLSurfaceView
 
+The below implementation implements a GLSurfaceView class. When the view's `onLayout` is called, the size of view is calculated and the game starts if the game doesn't start yet.
+
 ```java
 // ...
 import com.example.yourgame
@@ -110,8 +112,6 @@ public class EbitenGLSurfaceView extends GLSurfaceView {
     public void onLayout(boolean changed, int left, int top, int right, int bottom) {
         super.onLayout(changed, left, top, right, bottom);
         // Calculate the scale fitting the screen and use it.
-        // If you want to center this view, you can set `android:layout_centerHorizontal="true"` and
-        // `android:layout_centerVertical="true"` in the layout XML.
         double scaleInPx = getScaleInPx();
         getLayoutParams().width = (int)(Yourgame.ScreenWidth * scaleInPx);
         getLayoutParams().height = (int)(Yourgame.ScreenHeight * scaleInPx);
@@ -128,6 +128,38 @@ public class EbitenGLSurfaceView extends GLSurfaceView {
 }
 ```
 
+If you want to center this view, you can set `android:layout_centerHorizontal="true"` and `android:layout_centerVertical="true"` in the layout XML.
+
+## Implement a class implementing Renderer
+
+Implement a Renderer class to use for the GLSurfaceView class defined below.
+
+```java
+    private class EbitenRenderer implements Renderer {
+
+        private boolean mErrored;
+
+        @Override
+        public void onDrawFrame(GL10 gl) {
+            if (mErrored) {
+                return;
+            }
+            try {
+                // onDrawFrame is called every frame.
+                // Let's call your game's Update.
+                Yourgame.Update();
+            } catch (Exception e) {
+                Log.e("Go Error", e.toString());
+                mErrored = true;
+            }
+        }
+
+        // ...
+
+    }
+}
+```
+
 ## Dispatch touch events
 
 Call `mobile.UpdateTouchesOnAndroid` via your exported function.