如果我们需要快速提取图片和视频缩略图可以直接访问 android.provider.MediaStore.Images.Thumbnails 和android.provider.MediaStore.Video.Thumbnails这两个数据库，即可查询出来缩略图 。
如何判断文件呢? 可以通过Cursor遍历数据库，对比INTERNAL_CONTENT_URI字段的值，这是一个Uri，这里保存着Android手机SD卡上的多媒体文件完整路径。

1. [java]
   
2. Uri originalUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
   
3. //若为视频则为MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
   
4. ContentResolver cr = this.getContentResolver();
   
5. Cursor cursor = cr.query(originalUri, null, null, null, null);
   
6. if (cursor == null) {
   
7. return;
   
8. }
   
9. for (cursor.moveToFirst();!cursor.isAfterLast(); cursor.moveToNext()) {
   
10. long thumbNailsId = cursor.getLong(cursor .getColumnIndex("_ID"));
    
11. Bitmap bitmap = MediaStore.Images.Thumbnails.getThumbnail(cr,
    
12. thumbNailsId, Video.Thumbnails.MICRO_KIND, null);
    
13. //若为视频则为
    
14. // Bitmap bitmap = MediaStore.Video.Thumbnails.getThumbnail(cr,
    
15. // thumbNailsId, Video.Thumbnails.MICRO_KIND, null);
    
16. return bitmap;
    
17. }
    
18. Uri originalUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
    
19. //若为视频则为MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
    
20. ContentResolver cr = this.getContentResolver();
    
21. Cursor cursor = cr.query(originalUri, null, null, null, null);
    
22. if (cursor == null) {
    
23. return;
    
24. }
    
25. for (cursor.moveToFirst();!cursor.isAfterLast(); cursor.moveToNext()) {
    
26. long thumbNailsId = cursor.getLong(cursor .getColumnIndex("_ID"));
    
27. Bitmap bitmap = MediaStore.Images.Thumbnails.getThumbnail(cr,
    
28. thumbNailsId, Video.Thumbnails.MICRO_KIND, null);
    
29. //若为视频则为
    
30. // Bitmap bitmap = MediaStore.Video.Thumbnails.getThumbnail(cr,
    
31. // thumbNailsId, Video.Thumbnails.MICRO_KIND, null);
    
32. return bitmap;
    
33. }

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学习了。