How to use Soft/WeakReference classes in a Android App?

Question

I'm maintaining a big app with a huge number of images. My main problem is the app crashes when I use it because it produces out memory error. I'm trying to use SoftReferences and WeakReferences, I've read about it, but I don't know if I have to use them in Android classes like GridView, BaseAdapter or ImageView.

My app have a map Activity with markers which has a Gallery on the top. When I click over a balloon a second activity appears with a gridview.

The first activity, when I move the map the activity reload all the marker and images in the gallery and add new markers and images. It has the following attributes:

ShotButton shotButton; Gallery gallery; List images; private ImageView mMyLocationImage;

Dialog spinnerDialog;

private GoogleMap map;

private HashMap<String, Marker> identified_marker = new HashMap<String, Marker>();
private HashMap<Marker, DavinciImage> identified_XXX_images = new HashMap<Marker, XXXImage>();

private GalleryAdapter gallery_adapter;

private AsyncTask<Poi, Void, Void> refresh_pois_async = null;

@Override
public void onCreate(Bundle savedInstanceState) {
       ----
       new SoftReference<List<Object>>(XXXImages);
       new WeakReference<HashMap<String, Marker>>(identified_marker);
   new WeakReference<HashMap<Marker, XXXImage>>(identified_XXX_images);
    }

My question is when I move the map, destroy or pause the activity I have to do any new thing with soft/weakreference classes to free memory? Do I have to add a new attibute with a soft/weakreference class, e.g. the GalleryAdapter has to be added in a soft/weakReference class or the system free this memory for me?

The second activity has a gridview with all the images of the user. I load all the data when I enter to the activity and load the images when the activity needs. I have the following in this activity.

ImageView                   mUserImage;
public String               myApplicationUserId;
public GridAdapter          imageAdapter    = null;
public GridView             gridview        = null;
public ImageLoader_Profile  mImageLoaderMedium;


---
gridview.setScrollingCacheEnabled(true);
gridview.setFriction(10);

---
new WeakReference<ImageLoader_Profile>(mImageLoaderMedium);

The ImageLoader_Profile manage the load of images.

public class ImageLoader_Profile{

   MemoryCache                     memoryCache = new MemoryCache( );
   private Map< ImageView, String> imageViews  = Collections.synchronizedMap( new WeakHashMap< ImageView, String>( ));

   public ImageLoader_Profile( Context context, Bitmap canvas, int deviceDensity) {

       ....        
       new SoftReference<MemoryCache>(memoryCache);
       new SoftReference<Map<ImageView,String>>(imageViews);
   }

Is it all I need to do or I have to do anything else with soft references in this case? I'm a little confuse.

Answer 1

you should not soft /weak reference cache anymore.

It is changed that garbage collection process since Android 2.3,soft weak reference cache system is ineffective .

now, you should use LruCache,this is good :)

how to use LruCache? try this

Caching Bitmaps