Question

正如您在视频中看到的那样，ListView无法顺利滚动。

就像它总是从URL重新加载图像一样。

我想拥有的是它应该看起来流畅，如此专业。

当图像无效时，ImageView应该是不可见的并且为空。

我正在使用Universal-Image-Loader库。

这是我的代码。

String url = MainActivity.IMAGE_URL + "postid=" + model.get(position).getId();
loader.loadImage(url, new SimpleImageLoadingListener() {
    @Override
    public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
        holder.image.setVisibility(View.VISIBLE);
        holder.image.setImageBitmap(loadedImage);
    }

    @Override
    public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
        holder.image.setVisibility(View.GONE);
        holder.image.setImageBitmap(null);
    }

    @Override
    public void onLoadingCancelled(String imageUri, View view) {
        holder.image.setVisibility(View.GONE);
        holder.image.setImageBitmap(null);
    }
});

这里是完整的代码。

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    View view;
    if(convertView == null) {
        LayoutInflater inflater = LayoutInflater.from(context);
        view = inflater.inflate(R.layout.post_adapter, null);

        ViewHolder viewHolder = new ViewHolder();

        viewHolder.avatar = (ImageView) view.findViewById(R.id.post_avatar);
        viewHolder.title = (TextView) view.findViewById(R.id.post_title);
        viewHolder.time = (TextView) view.findViewById(R.id.post_time);
        viewHolder.text = (TextView) view.findViewById(R.id.post_text);
        viewHolder.image = (ImageView) view.findViewById(R.id.post_image);
        viewHolder.likes = (TextView) view.findViewById(R.id.post_likes);
        viewHolder.comments = (TextView) view.findViewById(R.id.post_comments);
        viewHolder.likeImage = (ImageView) view.findViewById(R.id.like_image);
        viewHolder.likeText = (TextView) view.findViewById(R.id.like_text);
        viewHolder.shareBtn = view.findViewById(R.id.share_btn);
        viewHolder.commentBtn = view.findViewById(R.id.comment_btn);
        viewHolder.likeBtn = view.findViewById(R.id.like_btn);

        view.setTag(viewHolder);
    } else {
        view = convertView;
    }
    final ViewHolder holder = (ViewHolder) view.getTag();

    final boolean hasLiked = model.get(position).isHasLiked();

    if(hasLiked) {
        holder.likeImage.setImageResource(R.drawable.ic_action_like_clicked);
        holder.likeText.setText(context.getString(R.string.dislike));
        holder.likeText.setTextColor(context.getResources().getColor(R.color.color_clicked));
    } else {
        ColorStateList textColor = holder.title.getTextColors();
        holder.likeImage.setImageResource(R.drawable.ic_action_like);
        holder.likeText.setText(context.getString(R.string.like));
        holder.likeText.setTextColor(textColor);
    }

    holder.title.setText(model.get(position).getTitle());

    ImageLoader loader = ImageLoader.getInstance();
    DisplayImageOptions options = new DisplayImageOptions.Builder()
            .showImageForEmptyUri(R.drawable.avatar)
            .showImageOnFail(R.drawable.avatar).build();

    loader.displayImage(model.get(position).getAvatar(), holder.avatar, options);

    String time = MainActivity.getTimeAgo(new Date(model.get(position).getTime() * 1000), context);
    holder.time.setText(time);

    if(model.get(position).getText().isEmpty()) {
        holder.text.setVisibility(View.GONE);
    } else {
        holder.text.setVisibility(View.VISIBLE);
        holder.text.setText(model.get(position).getText());
    }

    // HERE
    String url = MainActivity.IMAGE_URL + "postid=" + model.get(position).getId();
    loader.loadImage(url, new SimpleImageLoadingListener() {
        @Override
        public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
            holder.image.setVisibility(View.VISIBLE);
            holder.image.setImageBitmap(loadedImage);
        }

        @Override
        public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
            holder.image.setVisibility(View.GONE);
            holder.image.setImageBitmap(null);
        }

        @Override
        public void onLoadingCancelled(String imageUri, View view) {
            holder.image.setVisibility(View.GONE);
            holder.image.setImageBitmap(null);
        }
    });

    holder.likes.setText(String.valueOf(model.get(position).getLikes()));
    String comments = model.get(position).getComments() + " " + context.getString(R.string.comments);
    holder.comments.setText(comments);
    return view;
}

Answer 1

您可以使用额外的缓存功能扩展DisplayImageOptions。

DisplayImageOptions options = new DisplayImageOptions.Builder()
        .showImageForEmptyUri(R.drawable.avatar)
        .showImageOnFail(R.drawable.avatar)
        .cacheInMemory(true) // default is false
        .cacheOnDisk(true) // default is false
        .build();

来源：DisplayImageOptions

您还可以更改默认ImageLoaderConfiguration并更改缓存大小或增加线程优先级（如果您愿意）。请注意，与DisplayImageOptions不同，您只需在应用程序中设置一次此配置。请参阅：ImageLoaderConfiguration

Answer 2

我在尝试使用Universal ImageLoader，Picasso和Glide库后使用此代码，使用RecyclerView对我来说速度最快。

Uri uri = Uri.fromFile(new File(path));

Picasso.with(mContext)
.load(URL_OF_IMAGE)
.error(R.drawable.blank)
.config(Bitmap.Config.RGB_565)
.resizeDimen(R.dimen.d50dp, R.dimen.d50dp)
.centerCrop()
.into(holder.imageview);

检查此owesome链接，详细显示加载时间和内存的差异， https://inthecheesefactory.com/blog/get-to-know-glide-recommended-by-google/en

带有Image Loader的ListView无法加载效率

2 个答案: