Android: How does Bitmap recycle() work?

I think the problem is this: On pre-Honeycomb versions of Android, the actual raw bitmap data is not stored in VM memory but in native memory instead. This native memory is freed when the corresponding java Bitmap object is GC'd.

However, when you run out of native memory, the dalvik GC isn't triggered, so it is possible that your app uses very little of the java memory, so the dalvik GC is never invoked, yet it uses tons of native memory for bitmaps which eventually causes an OOM error.

At least that's my guess. Thankfully in Honeycomb and later, all bitmap data is stored in the VM so you shouldn't have to use recycle() at all. But for the millions of 2.3 users (fragmentation shakes fist), you should use recycle() wherever possible (a massive hassle). Or alternatively you may be able to invoke the GC instead.

The first bitmap is not garbage collected when you decode the second one. Garbage Collector will do it later whenever it decides. If you want to free memory ASAP you should call recycle() just before decoding the second bitmap.

If you want to load really big image you should resample it. Here's an example: Strange out of memory issue while loading an image to a Bitmap object.