android - 什么是实现 Viewholder 设计模式的最佳方式

Question

这些天我更多地处理自定义 ListView 和自定义 GridView。我使用 ViewHolder 类来实现平滑滚动。但是我注意到了一些奇怪的事情。当我向下滚动列表或 gridView 时，当我实现 ViewHolder 时，项目会不断重复，这在 Android 指南中是推荐的。但是当我从中初始化 View 时，项目不会重复。

请告诉我如何改进它。这让我可以流畅地滚动，而不会重复相同的项目。

public class GridAdapter extends BaseAdapter {
    Context context;
    Main values;
    LayoutInflater inflater;
    public GridAdapter(Context context, Main main){
        this.context=context;
        this.values=main;
        inflater = ( LayoutInflater )context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    @Override
    public int getCount() {
        return values.getPosts().size();
    }

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

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        ImageLoader imageLoader= ImageLoader.getInstance();
        ViewHolder viewHolder = null;
        if(convertView==null){
            viewHolder = new ViewHolder();
            convertView = inflater.inflate(R.layout.grid_item,parent,false);

            convertView.setTag(viewHolder);
        }
        else {
            viewHolder=(ViewHolder)convertView.getTag();
        }
        viewHolder.image=(ImageView)convertView.findViewById(R.id.thumbnail);
        viewHolder.title=(TextView)convertView.findViewById(R.id.title);
        viewHolder.title.setText(Html.fromHtml(values.getPosts().get(position).getTitle()));
        imageLoader.displayImage(values.getPosts().get(position).getThumbnail_images().getFull().getUrl(), viewHolder.image);
        return convertView;
    }

    private static class ViewHolder{
        public static ImageView image;
        public static TextView title;
    }
}

这段代码给了我重复的项目，是 Android 指南中推荐的方式:

public class GridAdapter extends BaseAdapter {
Context context;
Main values;
LayoutInflater inflater;
public GridAdapter(Context context, Main main){
    this.context=context;
    this.values=main;
    inflater = ( LayoutInflater )context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}

@Override
public int getCount() {
    return values.getPosts().size();
}

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

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    ImageLoader imageLoader= ImageLoader.getInstance();
    ViewHolder viewHolder = null;
    if(convertView==null){
        viewHolder = new ViewHolder();
        convertView = inflater.inflate(R.layout.grid_item,parent,false);
    viewHolder.image=(ImageView)convertView.findViewById(R.id.thumbnail);
    viewHolder.title=(TextView)convertView.findViewById(R.id.title);
        convertView.setTag(viewHolder);
    }
    else {
        viewHolder=(ViewHolder)convertView.getTag();
    }
    
    viewHolder.title.setText(Html.fromHtml(values.getPosts().get(position).getTitle()));
    imageLoader.displayImage(values.getPosts().get(position).getThumbnail_images().getFull().getUrl(), viewHolder.image);
    return convertView;
}

private static class ViewHolder{
    public static ImageView image;
    public static TextView title;
}
}

Answer 1

 public static ImageView image;
 public static TextView title;

错了。他们应该是

public ImageView image;
public TextView title;

没有 static 。这应该可以解决您的问题。您可以阅读有关静态关键字 here 的更多信息