android - 具有通用图像加载器的 ListView 自定义适配器错误地回收图像

Question

我已尝试实现建议的回收，如下面的代码所示。原因是 ListView 在滚动时滞后，回收 View 就解决了这个问题。但是，这也导致了另一个问题，即 ListView 项中加载的图像加载不正确。有些 View 没有图像，有些 View 有图像。当检查那些没有图像的项目时，UIL 有时会加载不同项目的图片。此外，当我不断上下滚动没有图像的其他项目时，也会获得归因于它们的图像。

这是自定义的ListViewAdapter:

public class CarListViewAdapter extends BaseAdapter {

// Declare Variables
Context context;
String[] name;
String[] owner;
String[] imageUrl;
String[] pricePerKm;
String[] pricePerH;
int amount;
int screenWidth;

ViewHolder viewHolder;

ImageLoader imageLoader;
DisplayImageOptions options;

public CarListViewAdapter(Context context, String[] imageUrl, String[] name, String[] owner,
                          String[] pricePerKm, String[] pricePerH, int amount, int screenWidth) {
    this.context = context;
    this.name = name;
    this.owner = owner;
    this.imageUrl = imageUrl;
    this.pricePerKm = pricePerKm;
    this.pricePerH = pricePerH;
    this.amount = amount;
    this.screenWidth = screenWidth;

    options = new DisplayImageOptions.Builder()
            .cacheOnDisk(true)
            .cacheInMemory(true)
            .bitmapConfig(Bitmap.Config.RGB_565)
            .imageScaleType(ImageScaleType.EXACTLY)
            .resetViewBeforeLoading(true)
            .build();
    ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(context)
            .defaultDisplayImageOptions(options)
            .threadPriority(Thread.MAX_PRIORITY)
            .threadPoolSize(5)
            .diskCacheExtraOptions(screenWidth, Math.round(screenWidth / 2), null)
            .memoryCache(new WeakMemoryCache())
            .denyCacheImageMultipleSizesInMemory()
            .build();
    imageLoader = ImageLoader.getInstance();
    imageLoader.init(config);
}

static class ViewHolder {
    ImageView image;
    TextView nameText;
    TextView ownerText;
    TextView pricePerKmText;
    TextView pricePerHText;
}

public View getView(int position, View convertView, ViewGroup parent) {
    if (convertView == null) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.car_list, parent, false);            
    }

    viewHolder = new ViewHolder();
    viewHolder.image = (ImageView) convertView.findViewById(R.id.car_image);
    viewHolder.nameText = (TextView) convertView.findViewById(R.id.car_name);
    viewHolder.ownerText = (TextView) convertView.findViewById(R.id.car_owner);
    viewHolder.pricePerKmText = (TextView) convertView.findViewById(R.id.car_price_km);
    viewHolder.pricePerHText = (TextView) convertView.findViewById(R.id.car_price_h);

    viewHolder.image.getLayoutParams().width = screenWidth;
    viewHolder.image.getLayoutParams().height = Math.round(screenWidth / 2);
    viewHolder.image.requestLayout();

    if (imageUrl[position] != null) {
        imageLoader.displayImage(imageUrl[position], viewHolder.image);
    }

    viewHolder.nameText.setText(name[position]);
    viewHolder.ownerText.setText(owner[position]);
    viewHolder.pricePerKmText.setText(pricePerKm[position]);
    viewHolder.pricePerHText.setText(pricePerH[position]);

    return convertView;
}


@Override
public int getCount() {
    return amount;
}

@Override
public Object getItem(int position) {
    return null;
}

@Override
public long getItemId(int position) {
    return 0;
}

Answer 1

When going over the ones that do not have an image the UIL sometimes does load a picture of a different item.

这是预期的行为，因为仅当 imageUrl[position] != null 时才设置项目。尝试为 imageUrl[position] 为 null 的位置设置占位符或隐藏 View 。这样你就不会拥有这种 Artifact 。

 if (imageUrl[position] != null) {
     imageLoader.displayImage(imageUrl[position], viewHolder.image);
 } else {
    viewHolder.image.setImageResource(R.drawable.place_holder);
 }