Including the switch folders,dynamic record user selected pictures and preview images, etc
On the basis of this Demo Zhang Hongyang blog Android 超高仿微信图片选择器图片该这么加载，Major point of modification is as follows：
- 1、According to user selection dynamic display the number of the selected images
- 2、Increase the image preview function
- 2.1：There are two pictures preview entry：①Click on the gridview image preview area (image upper right)；②Click the preview button in the lower-right corner of the window
- 2.2：Pictures can be zoom 、shrink in the preview images interface
- 2.3: In picture preview interface , you can select and deselect images，After exit picture preview interface，"depending on the situation" dynamic refresh the selection state of the pictures in the ImageGridShowActivity interface
- 2.4：The above "depending on the situation" has the following two kinds：
- 2.4.1: If the user click preview images, just preview images and did not do any operation selected, deselect photoes, so will not refresh ImageGridShowActivity interface when the user exit preview image interface
- 2.4.2：If the user go in the interface when the selected images and exit the interface is different,so in the exit interface when dynamic refresh ImageGridShowActivity interface
- 2.5：In the preview interface processing OOM
- 2.6：To monitor physical return key, dynamic refresh ImageGridShowActivity interface
- 2.1：There are two pictures preview entry：①Click on the gridview image preview area (image upper right)；②Click the preview button in the lower-right corner of the window
- 3、Modify the style of the interface
- 3.1：Folder name does not display the problem
- 3.2：File name error display problems
- 3.3：Folders are selected by default problems
- 3.4：The style of the folder options problems
- 4、The division of regional and preview images selected images
- 5、Optimize createAdapter() method, adapter created only once
- 6、Folder and images in reverse chronological order