Android-code-bitmapcche

代碼也是來自vlc 0.9.9版本。

裡面使用了LruCache這個類。既可以緩存資源檔案裡的，又可以用String來辨別的Bitmap。以後就可以拿來直接用了。

有關LruCache的介紹可以參考下面的文章：

​​Android提供的LruCache類簡介​​

public class BitmapCache {

    public final static String TAG = "VLC/BitmapCache";
    private final static boolean LOG_ENABLED = false;

    private static BitmapCache mInstance;
    private final LruCache<String, Bitmap> mMemCache;

    public static BitmapCache getInstance() {
        if (mInstance == null)
            mInstance = new BitmapCache();
        return mInstance;
    }

    private BitmapCache() {

        // Get the global context of the application
        Context context = VLCApplication.getAppContext();

        // Get memory class of this device, exceeding this amount will throw an
        // OutOfMemory exception.
        final int memClass = ((ActivityManager) context.getSystemService(
                Context.ACTIVITY_SERVICE)).getMemoryClass();

        // Use 1/5th of the available memory for this memory cache.
        final int cacheSize = 1024 * 1024 * memClass / 5;

        Log.d(TAG, "LRUCache size sets to " + cacheSize);

        mMemCache = new LruCache<String, Bitmap>(cacheSize) {

            @Override
            protected int sizeOf(String key, Bitmap value) {
                return value.getRowBytes() * value.getHeight();
            }

        };
    }

    public Bitmap getBitmapFromMemCache(String key) {
        final Bitmap b = mMemCache.get(key);
        if (LOG_ENABLED)
            Log.d(TAG, (b == null) ? "Cache miss" : "Cache found");
        if (b != null && b.isRecycled()) {
            /* A recycled bitmap cannot be used again */
            mMemCache.remove(key);
            return null;
        }
        return b;
    }

    public void addBitmapToMemCache(String key, Bitmap bitmap) {
        if (key != null && bitmap != null && getBitmapFromMemCache(key) == null)
            mMemCache.put(key, bitmap);
    }

    private Bitmap getBitmapFromMemCache(int resId) {
        return getBitmapFromMemCache("res:" + resId);
    }

    private void addBitmapToMemCache(int resId, Bitmap bitmap) {
        addBitmapToMemCache("res:" + resId, bitmap);
    }

    public void clear() {
        mMemCache.evictAll();
    }

    public static Bitmap GetFromResource(View v, int resId) {
        BitmapCache cache = BitmapCache.getInstance();
        Bitmap bitmap = cache.getBitmapFromMemCache(resId);
        if (bitmap == null) {
            bitmap = BitmapFactory.decodeResource(v.getResources(), resId);
            cache.addBitmapToMemCache(resId, bitmap);
        }
        return bitmap;
    }
}