Question

我似乎无法弄清为什么我无法加载任何类型的图像（我尝试过多个URL）。我尝试使用AsyncTask类，但该问题仍未解决。下面列出了我的适配器类，将不胜感激。

我正在尝试为每个RecyclerView条目加载一个图像（在此测试用例中，为同一图像）。当我不尝试设置从URL派生的图像时，会出现默认视图（橙色正方形），但是如果我尝试设置它，则ImageView只是留空。

EntryAdapter

public class EntryAdapter extends RecyclerView.Adapter<EntryAdapter.EntryViewHolder> {
private Entry[] mDataset;

// Provide a reference to the views for each data item
// Complex data items may need more than one view per item, and
// you provide access to all the views for a data item in a view holder
public static class EntryViewHolder extends RecyclerView.ViewHolder {
    // each data item is just a string in this case
    public String source;
    public TextView textContent, title, label, author;
    public ImageView thumbnail;
    public CardView topCard, mainCard;
    public EntryViewHolder(View v) {
        super(v);
        title = v.findViewById(R.id.title);
        textContent = v.findViewById(R.id.textContent);
        topCard = v.findViewById(R.id.top_card);
        mainCard = v.findViewById(R.id.main_card);
        thumbnail = mainCard.findViewById(R.id.thumbnail);
        author = mainCard.findViewById(R.id.author);
        label = topCard.findViewById(R.id.label);
    }
}

// Provide a suitable constructor (depends on the kind of dataset)
public EntryAdapter(Entry[] myDataset) {
    mDataset = myDataset;
}

// Create new views (invoked by the layout manager)
@Override
public EntryAdapter.EntryViewHolder onCreateViewHolder(ViewGroup parent,
                                                 int viewType) {
    // create a new view
    View v = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.entry_item_constraints, parent, false);

    EntryViewHolder vh = new EntryViewHolder(v);
    return vh;
}

// Replace the contents of a view (invoked by the layout manager)
@Override
public void onBindViewHolder(EntryViewHolder holder, int position) {
    // - get element from your dataset at this position
    // - replace the contents of the view with that element
    holder.title.setText(mDataset[position].getTitle());
    holder.label.setText(mDataset[position].getLabel());
    holder.textContent.setText(mDataset[position].getTextContent());
    holder.thumbnail.setImageDrawable(LoadImageFromWebOperations(mDataset[position].getThumbnail()));
    holder.author.setText(mDataset[position].getAuthor());

    //new DownloadImageTask(holder.thumbnail).execute(mDataset[position].getThumbnail());
}

// Return the size of your dataset (invoked by the layout manager)
@Override
public int getItemCount() {
    return mDataset.length;
}

public static Drawable LoadImageFromWebOperations(String url) {
    try {
        InputStream is = (InputStream) new URL(url).getContent();
        Drawable d = Drawable.createFromStream(is, "reddit_thumbnail");
        return d;
    } catch (Exception e) {
        return null;
    }
}
}

Answer 1

尝试使用Glide在RecyclerView中显示图像，该图像处理延迟加载以使列表更平滑地滚动。当滚动列表以提高性能和资源消耗时，它也会取消加载操作。

Glide.with(holder.thumbnail.getContext())
         .load(mDataset[position].getThumbnail())
         .into(holder.thumbnail);

在应用级别 build.gradle：

repositories {
    mavenCentral()
    google()
}

dependencies {
    implementation 'com.github.bumptech.glide:glide:4.8.0'
    annotationProcessor 'com.github.bumptech.glide:compiler:4.8.0'
}

您还可以使用placeholder()方法来指定图像（例如，它可能指向使用资源ID的可绘制对象），以在未下载或无法使用目标图像时显示该图像。

无法从RecyclerView中的URL加载图像

1 个答案: