listview - Android中的Listview延迟加载平滑

Question

我有一个显示产品的 ListView。每个产品都有产品详细信息和 ImageView，但问题是我正在为产品图像进行延迟加载。并且图像是高分辨率的。滚动时它变得粘糊糊（不平滑）。因为下载图像需要时间。同样的方式 facebook 有他们的图像，但滚动更顺畅任何解决方案请帮助。

Answer 1

public class BitmapCacheManager {
    private static LruCache<Object, Bitmap> cache = null;
    private final Context context;
    private static final int KB = 1024;
    private final Drawable placeHolder;


    public BitmapCacheManager(Context context) {
        this.context = context;
        placeHolder = context.getResources().getDrawable(R.drawable.unknown);
        int maxMemory = (int) (Runtime.getRuntime().maxMemory() / KB);
        int cacheSize = maxMemory / 7;
        cache = new LruCache<Object, Bitmap>(cacheSize) {
            @Override
            protected int sizeOf(Object albumId, Bitmap bitmap) {
                return (bitmap.getRowBytes() * bitmap.getHeight() / KB);
            }

            protected void entryRemoved(boolean evicted, Object key, Bitmap oldValue, Bitmap newValue) {
                oldValue.recycle();
            }
        };
    }

    public void addBitmapToMemoryCache(Object key, Bitmap bitmap) {
        if (bitmap != null && key != null && cache.get(key) == null)
            cache.put(key, bitmap);
    }

    public Bitmap getBitmapFromMemCache(Object key) {
        return cache.get(key);
    }

    public void loadBitmap(final Object key, final ImageView imageView) {
        final Bitmap bitmap = getBitmapFromMemCache(key);
        if (bitmap != null) {
            imageView.setImageBitmap(bitmap);
        } else {
            imageView.setImageDrawable(placeHolder);
            BitmapWorker task = new BitmapWorker(imageView);
            task.execute(key);
        }
    }

    private class BitmapWorker extends AsyncTask<Object, Void, Bitmap> {
        private final ImageView imageView;
        private Object key;

        public BitmapWorker(final ImageView imageView) {
            this.imageView = imageView;
        }

        @Implement
        protected Bitmap doInBackground(Object... params) {
            key = params[0];
            final Bitmap b = SomeClass.GetSomeBitmap(context, key);
            addBitmapToMemoryCache(key, b);
            return b;
        }

        @Override
        protected void onPostExecute(final Bitmap bitmap) {
            if (bitmap == null) {
                imageView.setImageBitmap(SomeClass.DefaultBitmap);
                return;
            }
            if (imageView.getTag().toString().equalsIgnoreCase(key.toString()) && !bitmap.isRecycled())
                imageView.setImageBitmap(bitmap);
        }
    }

}

and call:

bitmapCacheManager.loadBitmap(somekey, someImageView);

Answer 2

1. 将虚拟图像添加到所有占位符，因此滚动工作顺利。
2. 使用异步任务根据需要获取图像，并在图像准备好后将虚拟图像替换为正确的图像。
3. 使用适当的命名约定缓存图像，并根据您的图像大小正确选择缓存大小。