最有效的显示图像的方式

Question

My app uses 29 images in 2 different classes (and layouts). In 1 layout there is 1 image view that changes between at most 25 of the images, and then the other layout is a scroll view that contains all images where at most 3 or 4 are visible on screen at a time. Previously I had the images saved as .jpg and each is 720*540 and around 200-300kb in size. My app has had out of memory issues after going between my 2 layouts that are using the images; it is using over 100 mb. I did some research on bitmaps and tried them for my images, but they didn't help much because I still get out of memory issues and they increased the .apk size by almost 3 times. What is the most preferred way to load images, is it as a drawable from a .jpg or from a bitmap or some other way? Any suggestions would be appreciated.

Answer 1

when the bitmap is in memory, it's uncompressed. the original format doesn't matter. you can count on each image taking about width * height * 4 bytes of memory. eg, each of your 720x540 images will take ~1.5MB of memory.

it does not matter where you load them from, at least as far as the amount of memory required.

now read this,

http://developer.android.com/training/displaying-bitmaps/cache-bitmap.html

Answer 2

You can read the source code of system Gallery, then you can totally understand how to operate bitmap. When you get an image at first time, you have to decode the original file, and save it to cache file. Then for the next time, you just decode the cache file, which is faster. Your memory is limited. Don't expect to store all your bitmaps, just the bitmap that you wanna show on the screen. The size of thumbnail is much smaller than full image. So there is no problem if you wanna put 8 ~ 10 thumbnails on screen. When users click the thumbnail to browse the full image, you can load the full image into memory, and recycle other bitmaps.