增加注释

student/src/main/java/com/cooleshow/student/helper/ShareHelper.java

@@ -361,6 +361,7 @@ public class ShareHelper {
 
 
     public static Bitmap createBitmapByView(View view) {
+        //这种方式只适用于view正在显示的
         view.buildDrawingCache();
         Bitmap bitmap = view.getDrawingCache();
         return bitmap;