Bitmap Cache

Introduction

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

  • 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

ParameterDetails
keykey to store bitmap in memory cache
bitmapbitmap value which will cache into memory

Bitmap Cache Using LRU Cache

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").

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