在 ListView (Android Studio) 的自定义适配器中从 URL 加载图像 [英] Loading image from URL in custom adapter for ListView (Android Studio)

问题描述

虽然位图似乎被正确获取，但变量userBitmap"将保持为空.但是，在我的平板电脑上向上或向下滚动时，新的列表行将包含图片，但它们都是相同且错误的.真的，真的很迷茫.我尝试了许多不同的方法来从网络获取图像.非常感谢任何帮助.

While the bitmap seems to be fetched right, the variable 'userBitmap' will remain null. When scrolling up or down on my tablet, though, new list rows will contain the pictures, but they're all the same and wrong. Really, really confused. I've tried a number of different methods getting an image from the web. Any help is greatly appreciated.

我的自定义适配器:

public class MessagesArrayAdapter extends ArrayAdapter<ChatData>
{
    Bitmap userBitmap;

public MessageArrayAdapter(Context context, List<ChatData> objects)
{
    super(context, 0, objects);
}

public View getView(int position, View convertView, ViewGroup parent)
{
    ChatCell chatCell = new ChatCell();

    LayoutInflater inflater = LayoutInflater.from(getContext());
    convertView = inflater.inflate(R.layout.cell_chat, parent, false);

    chatCell.usernameTextView = (TextView) convertView.findViewById(R.id.usernameTextView);
    chatCell.messageTextView = (TextView) convertView.findViewById(R.id.messageTextView);
    chatCell.userImageView = (ImageView) convertView.findViewById(R.id.userImageView);

    ChatData chatData = getItem(position);

    // Get user image from web
    new loadImageAsync().execute(chatData.avatarURL);

    chatCell.userImageView.setImageBitmap(userBitmap);
    chatCell.usernameTextView.setText(chatData.username);
    chatCell.messageTextView.setText(chatData.message);

    return convertView;
}



private static class ChatCell
{
    TextView usernameTextView;
    TextView messageTextView;
    ImageView userImageView;
}

private class loadImageAsync extends AsyncTask<String, Void, Double>{
    @Override
    protected Double doInBackground(String... params) {

        userBitmap = loadImage(params[0]);


        return null;
    }
}


public Bitmap loadImage(String str) {

    InputStream instream = null;
    try {
        HttpGet httpRequest = new HttpGet(URI.create(str));
        HttpClient httpclient = new DefaultHttpClient();
        HttpResponse response = (HttpResponse) httpclient.execute(httpRequest);
        HttpEntity entity = response.getEntity();
        BufferedHttpEntity bufHttpEntity = new BufferedHttpEntity(entity);
        instream = bufHttpEntity.getContent();
        Bitmap myBitmap = BitmapFactory.decodeStream(instream);

        return myBitmap;
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    } finally {
        //close input
        if (instream != null) {
            try {
                instream.close();
            } catch (IOException ioex) {
                // Handle error
            }
        }
    }

}

}

推荐答案

解决问题的最简单方法是使用一些库，例如 毕加索.它不仅更易于使用并使您的代码更易于阅读，而且还可以防止您在图像太大时出现 OutOfMemory 异常.加载图像则是一行:

The easiest way to solve your problem is using some library, for example Picasso. It is not only easier to use and make your code easier to read, but also prevents you from OutOfMemory Exceptions, when images are too big. Loading image is then matter of one line:

Picasso.with(context)
.load(urlOfYourImage)
.resize(50, 50) // here you resize your image to whatever width and height you like
.into(imageView)

这篇关于在 ListView (Android Studio) 的自定义适配器中从 URL 加载图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！