Useful Info

1. Caching is NOT enabled by default. If you want loaded images will be cached in memory and/or on disc then you should enable caching in DisplayImageOptions this way:

// Create default options which will be used for every 
//  displayImage(...) call if no options will be passed to this method
DisplayImageOptions defaultOptions = new DisplayImageOptions.Builder()
			...
            .cacheInMemory()
            .cacheOnDisc()
            ...
            .build();
ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(getApplicationContext())
            ...
            .defaultDisplayImageOptions(defaultOptions)
            ...
            .build();
ImageLoader.getInstance().init(config); // Do it on Application start

// Then later, when you want to display image
ImageLoader.getInstance().displayImage(imageUrl, imageView); // Default options will be used

or this way:

DisplayImageOptions options = new DisplayImageOptions.Builder()
			...
            .cacheInMemory()
            .cacheOnDisc()
            ...
            .build();
ImageLoader.getInstance().displayImage(imageUrl, imageView, options); // Incoming options will be used

2. If you enabled disc caching then UIL try to cache images on external storage (/sdcard/Android/data/[package_name]/cache). If external storage is not available then images are cached on device's filesytem. To provide caching on external storage (SD card) add following permission to AndroidManifest.xml:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

3. How UIL define Bitmap size needed for exact ImageView? It searches defined parameters:

• Get android:layout_width and android:layout_height parameters
• Get android:maxWidth and/or android:maxHeight parameters
• Get maximum width and/or height parameters from configuration (memoryCacheExtraOptions(int, int) option)
• Get width and/or height of device screen

So try to set android:layout_width|android:layout_height or android:maxWidth|android:maxHeight parameters for ImageView if you know approximate maximum size of it. It will help correctly compute Bitmap size needed for this view and save memory.

4. If you often got OutOfMemoryError in your app using Universal Image Loader then try next (all of them or several):

• Reduce thread pool size in configuration (.threadPoolSize(...)). 1 - 5 is recommended.
• Use .bitmapConfig(Bitmap.Config.RGB_565) in display options. Bitmaps in RGB_565 consume 2 times less memory than in ARGB_8888.
• Use .memoryCache(new WeakMemoryCache()) in configuration or disable caching in memory at all in display options (don't call .cacheInMemory()).
• Use .imageScaleType(ImageScaleType.IN_SAMPLE_INT) in display options. Or try .imageScaleType(ImageScaleType.EXACTLY).
• Avoid using RoundedBitmapDisplayer. It creates new Bitmap object with ARGB_8888 config for displaying during work.

5. For memory cache configuration (ImageLoaderConfiguration.Builder.memoryCache(...)) you can use already prepared implementations:

• UsingFreqLimitedMemoryCache (The least frequently used bitmap is deleted when cache size limit is exceeded) - Used by default
• LRULimitedMemoryCache (Least recently used bitmap is deleted when cache size limit is exceeded)
• FIFOLimitedMemoryCache (FIFO rule is used for deletion when cache size limit is exceeded)
• LargestLimitedMemoryCache (The largest bitmap is deleted when cache size limit is exceeded)
• LimitedAgeMemoryCache (Decorator. Cached object is deleted when its age exceeds defined value)
• WeakMemoryCache (Memory cache with only weak references to bitmaps)

6. For disc cache configuration (ImageLoaderConfiguration.Builder.discCache(...)) you can use already prepared implementations:

• UnlimitedDiscCache (The fastest cache, doesn't limit cache size) - Used by default
• TotalSizeLimitedDiscCache (Cache limited by total cache size. If cache size exceeds specified limit then file with the most oldest last usage date will be deleted)
• FileCountLimitedDiscCache (Cache limited by file count. If file count in cache directory exceeds specified limit then file with the most oldest last usage date will be deleted. Use it if your cached files are of about the same size.)
• LimitedAgeDiscCache (Size-unlimited cache with limited files' lifetime. If age of cached file exceeds defined limit then it will be deleted from cache.)

NOTE: UnlimitedDiscCache is 30%-faster than other limited disc cache implementations.

7. To display bitmap (DisplayImageOptions.Builder.displayer(...)) you can use already prepared implementations:

• RoundedBitmapDisplayer (Displays bitmap with rounded corners)
• FadeInBitmapDisplayer (Displays image with "fade in" animation)

8. To avoid list (grid, ...) scrolling lags you can use PauseOnScrollListener:

boolean pauseOnScroll = false; // or true
boolean pauseOnFling = true; // or false
PauseOnScrollListener listener = new PauseOnScrollListener(pauseOnScroll, pauseOnFling);
listView.setOnScrollListener(listener);