CODEWITHSUNDEEP
javaandroid
Muhammad Babar
Muhammad Babar

Reputation: 8134

Caching Bitmap bug at developer.android.com

I was just reading tutorial of caching bitmaps from url at developer.android.com

refering to code

    private LruCache<String, Bitmap> mMemoryCache;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
        // 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 1/8th of the available memory for this memory cache.
        final int cacheSize = 1024 * 1024 * memClass / 8;

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

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

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

public void loadBitmap(int resId, ImageView imageView) {
    final String imageKey = String.valueOf(resId);

    final Bitmap bitmap = getBitmapFromMemCache(imageKey);
    if (bitmap != null) {
        mImageView.setImageBitmap(bitmap);
    } else {
        mImageView.setImageResource(R.drawable.image_placeholder);
        BitmapWorkerTask task = new BitmapWorkerTask(mImageView);
        task.execute(resId);
    }
}

in activity cache is beign initialize and there are two methods

  1. addBitmapToMemoryCache(String key, Bitmap bitmap)

  2. getBitmapFromMemCache(String key)

here is the BitmapWorkerTask class

class BitmapWorkerTask extends AsyncTask<Integer, Void, Bitmap> {
    ...
    // Decode image in background.
    @Override
    protected Bitmap doInBackground(Integer... params) {
        final Bitmap bitmap = decodeSampledBitmapFromResource(
                getResources(), params[0], 100, 100));
        addBitmapToMemoryCache(String.valueOf(params[0]), bitmap);
        return bitmap;
    }
    ...
}

now my question is that in BitmapWorkerTask class how come method addBitmapToMemoryCache(String.valueOf(params[0]), bitmap); is called with having any reference to the methods that are defined in Activty or might be in some other Class

Upvotes: 1

Views: 409

Answers (2)

Vishnuprasad R
Vishnuprasad R

Reputation: 1730

For someone who still couldn't get the sample code work,

In order to get the code working, you should make BitmapWorkerTask class an inner class and then change its two static functions 

public  static int calculateInSampleSize()
public  static Bitmap decodeSampledBitmapFromResource()

to normal (non static) methods

Upvotes: 0

rennoDeniro
rennoDeniro

Reputation: 928

The BitmapWorkerTask is probably an inner class within the activity, thus providing it access to the defined methods.

Upvotes: 2

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