Question

我有一个android listView，我用图片填充。

我通过静默分页从服务器加载列表。

我使用异步下载任务下载图像和缓存层以保留它们。

每当我的适配器执行getView时，它都会将图像标记设置为其URL。

然后在我将drawable加载到图像视图之前，我检查它仍然是相关的（因为它是异步任务并且滚动可能已经移动并且该项目已经被回收）通过将下载的url与保存在其中的url进行比较。标签

但是我看到通常只看到默认图像，

我的逻辑缺少什么？

private final LruCache<String, Bitmap> imageCache = new LruCache<String, Bitmap>(
        100);

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        if (position != 0
                && (PublicMacros.OFFERS_PAGE_SIZE / 2 == position)
                && ((position / PublicMacros.OFFERS_PAGE_SIZE + 1)
                        * PublicMacros.OFFERS_PAGE_SIZE + 1) > mOffersList
                            .size() && lastTriggeringPosition != position)
        // ask next page
        // maybe add loader
        {
            lastTriggeringPosition = position;
            mOffersListActivity.getOffersFromServer(++pageNumber,
                    PublicMacros.OFFERS_PAGE_SIZE);
        }
        if (convertView == null) {

            LayoutInflater inflater = (LayoutInflater) mOffersListActivity
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.offer_list_item, null);
        } else {
            // fetch existing data
        }

        initLayout(position, convertView);


        setChangeableViews(convertView);

        return convertView;


    }


//called in setChangeableViews
    private void setItemBgImage(View convertView) {
        String imageUrl = getImageUrlFromOffer(convertView);
        Bitmap bitmap = imageCache.get(imageUrl);

        // anyhow set to default image
        Drawable dr = mOffersListActivity.getResources().getDrawable(
                R.drawable.lock_closed);
        ImageView offerImage = ((ImageView) convertView
                .findViewById(R.id.offerImage));
        if (bitmap != null) {
            dr = new BitmapDrawable(
            // bitmap compression code
                    mOffersListActivity.getResources(), bitmap);
        } else {

            // check if already in the process of downloading
            if (!downloadingImageUrls.contains(imageUrl)) {
                downloadingImageUrls.add(imageUrl);
                new DownloadImageAsyncTask2(offerImage).execute(imageUrl);
            }
        }
        offerImage.setImageDrawable(dr);
        offerImage.setTag(imageUrl);
    }




public class DownloadImageAsyncTask2 extends
            AsyncTask<String, Void, Bitmap> {
        private final ImageView imageView;
        private String imageUrl;

        public DownloadImageAsyncTask2(ImageView imageView) {
            this.imageView = imageView;
        }

        @Override
        protected void onPreExecute() {
            Log.i("DownloadImageAsyncTask", "Starting image download task...");
        }

        @Override
        protected Bitmap doInBackground(String... params) {
            imageUrl = params[0];
            try {
                return BitmapFactory.decodeStream((InputStream) new URL(
                        imageUrl).getContent());
            } catch (IOException e) {
                Log.e("DownloadImageAsyncTask", "Error reading bitmap" + e);
                downloadingImageUrls.remove(imageUrl);
            }
            return null;
        }
}

Answer 1

您可以参考此库。

这是一个用于在Android上加载，缓存和显示图像的库。

https://github.com/nostra13/Android-Universal-Image-Loader

为什么我的listView只设置为默认图像？

1 个答案: