Question

I’m developing a small social networking app that makes use of something like profile pictures. Images are stored on a server and I have scripts set up that will send the image for each user to the app, which then displays it in an image view for each user, and then saves the image to external storage. The way I have it implemented now is that anytime the app needs the image after it downloads it from the server, the app will get the image from external storage unless a user has uploaded a new image (I thought this would be faster than redownloading it from the server every time). However, it seems to be taking longer to get the file from external storage than it does to get it from my server (and the server is pretty slow, running on wifi from 3 floors away…budget constrains 🙂 ).

My question is what is the fastest way to get these images if the user hasn’t uploaded a new one. Should I just downlaod it from the server everytime (I’m assuming not) or is there a better place in the filesystem to store the images that makes for faster retrieval?

Answer 1

Loading images from the SD card should be very fast. Some strategies:

1. Do it only once – Load the images into memory asynchronously when your activity or application starts. You don’t want to be hitting the SD card every time your view updates.
2. Make them small – If you’re having performance problems displaying thumbnails in a list, try saving your thumbnails as smaller images using inSampleSize to put less pressure on the decoder.
3. Use internal memory – I think that internal memory is faster, but it tends to be in short supply. You could certainly store some number of thumbnails in your cache directory to help speed up step 1.
4. Responsiveness over performance – The golden rule is to remember that absolute performance does not always correlate with responsiveness. Even if the images take a long time to load, choosing cleverly when to load the images can have a great impact on the user’s perception of speed.