Android : Trouble deleting image files in android private directory

I created a custom camera application that saves images on an app private directory for instance File myImage = new File(context.getDir("resource",0),"myImage.png");

But the problem starts when I have to remove the file now. Using file.detele(); and using deleteFile(file.getPath());

sometimes it works but most of the time it doesn't. My question is that is there any convenient and fast way to to delete files and/or directories