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Android Bitmap Cache

From WikiOD

Memory efficient bitmap caching: This is particularly important if your application uses animations as they will be stopped during GC cleanup and make your application appears sluggish to the user. A cache allows reusing objects which are expensive to create. If you load on object into memory, you can think of this as a cache for the object.Working with bitmap in android is tricky.It is more important to cache the bimap if you are going to use it repeatedly.

Syntax[edit | edit source]

  • LruCache<String, Bitmap> mMemoryCache;//declaration of LruCache object.
  • void addBitmapToMemoryCache(String key, Bitmap bitmap){}//declaration of generic method adding bitmap into cache memory
  • Bitmap getBitmapFromMemCache(String key){}//declaration of generic method for get bimap from cache.

Parameters[edit | edit source]

Parameter Details
key key to store bitmap in memory cache
bitmap bitmap value which will cache into memory

Bitmap Cache Using LRU Cache[edit | edit source]

LRU Cache

The following example code demonstrates a possible implementation of the LruCache class for caching images.

private LruCache<String, Bitmap> mMemoryCache;

Here string value is key for bitmap value.

// Get max available VM memory, exceeding this amount will throw an
// OutOfMemory exception. Stored in kilobytes as LruCache takes an
// int in its constructor.
final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);

// Use 1/8th of the available memory for this memory cache.
final int cacheSize = maxMemory / 8;

mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {
    @Override
    protected int sizeOf(String key, Bitmap bitmap) {
        // The cache size will be measured in kilobytes rather than
        // number of items.
        return bitmap.getByteCount() / 1024;
    }
};

For add bitmap to the memory cache

public void addBitmapToMemoryCache(String key, Bitmap bitmap) {
if (getBitmapFromMemCache(key) == null) {
        mMemoryCache.put(key, bitmap);
    }    
}

For get bitmap from memory cache

public Bitmap getBitmapFromMemCache(String key) {
    return mMemoryCache.get(key);
}

For loading bitmap into imageview just use getBitmapFromMemCache("Pass key").

Credit:Stack_Overflow_Documentation