I am developing an android application where it will select some photos from the gallery and hide them,
i am able to select particular picture from gallery and store it in my app and delete it from gallery,but a person can see those pictures if he opens my app folder in sdcard ,so how do i store them such that even if a person checks my sdcard then he should not be able to detect those pictures ?
The only secure way to do this is to encrypt the image data yourself and remove the original files, leaving only your application able to decrypt the files.
Take a look at How to encrypt file from SD card using AES in Android? to see how this can be done.
As an additional step, you can also use any number of the other answers to hide the encrypted files