android - picasso 每次滚动时都会在 ListView 中刷新图像

Question

我有一个 ListView，它会在我每次上下滚动时不断刷新图像

我正在从我提供给 Picasso 的 JSON 中选择图像 url。

我正在使用 Picasso 加载图像。

所有图像的总大小为 516kb，我知道，我不认为这是缓存问题，因为图像大小实际上很小。

老实说，我在S.O上研究过这个问题，还没有看到任何好的解决方案。

也许这个问题与 Picasso 无关，也许我的实现实际上是错误的。我需要更多这方面的知识。

下面是我的代码。

public class ImageAdapter extends ArrayAdapter<Genres> {

    ArrayList<Genres> movieList;
    TextView movietitle, moviecategory;

    LayoutInflater vi;
    int Resource;
    ViewHolder holder;

    private Context mContext;

    public ImageAdapter(Context context, int resource, ArrayList<Genres> objects) {
        super(context, resource, objects);
        vi = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        Resource = resource;
        movieList = objects;
        mContext = context;
    }

    // create a new ImageView for each item referenced by the Adapter
    public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        ImageView imageView;
        if (v == null) {
            holder = new ViewHolder();
            v = vi.inflate(Resource, null);

            holder.imageview = (ImageView) v.findViewById(R.id.movieimage);

            LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(96, 128);
            holder.imageview.setLayoutParams(layoutParams);
            holder.imageview.setScaleType(ImageView.ScaleType.CENTER_CROP);
            holder.imageview.setPadding(4, 4, 4, 4);
            holder.imageview.setAdjustViewBounds(true);

            holder.movietitle = (TextView) v.findViewById(R.id.movietitle);
            holder.moviecategory = (TextView) v.findViewById(R.id.moviecategory);

            v.setTag(holder);

        } else {
            holder = (ViewHolder) v.getTag();
        }

        Picasso.with(mContext)
        .load(movieList.get(position).getImage())
        .noFade()
        .into(holder.imageview);

        holder.movietitle.setText(movieList.get(position).getMoviename());
        holder.moviecategory.setText(movieList.get(position).getCategory());

        return v;
    }

    static class ViewHolder {
        public ImageView imageview;
        public TextView movietitle;
        public TextView moviecategory;
    }

}

Answer 1

我认为您在这里遇到的问题是您将 holder 对象设为适配器类的实例变量，因此实际上您只有一个 View holder。

尝试删除实例变量声明

LayoutInflater vi;
int Resource;
ViewHolder holder;    // remove or comment out this line 

private Context mContext;

然后创建新的 View 持有者和 getTag()

返回的 View 持有者

局部变量。

所以这两个变化:

首先:

if (v == null) {
   // holder = new ViewHolder();
   ViewHolder holder = new ViewHolder();  // replace above commented line with this line
   v = vi.inflate(Resource, null);

然后在你的 else 子句中:

    } else {
    //    holder = (ViewHolder) v.getTag();
          ViewHolder holder = (ViewHolder) v.getTag(); // replace above commented line with this one.
    }

现在布局存储的 holder 将是不同的 View ，而不是您当前拥有的唯一一个 View 。

作为引用，我在 Picasso 中使用了一个适配器。有几个不同之处，但我认为最主要的是您对 viewHolder 变量使用单个实例变量。

public class FollowedUsersListAdapter extends ArrayAdapter<UserListItem> {
    private final Context context;
    private final ArrayList<UserListItem> values;

    public FollowedUsersListAdapter(Context context, ArrayList<UserListItem> values) {
        super(context, R.layout.row_layout, values);
        this.context = context;
        this.values = values;
    }

    static class ViewHolder {
        public TextView userNameView;
        public TextView lastPostView;
        public TextView postedTimeAgoView;
        public ImageView imageView;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        View followedUserView = convertView;
        if (followedUserView == null) {
            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            followedUserView = inflater.inflate(R.layout.followed_user_item_layout, parent, false);
            ViewHolder viewHolder = new ViewHolder();
            viewHolder.userNameView = (TextView) followedUserView.findViewById(R.id.user_name);
            viewHolder.lastPostView = (TextView) followedUserView.findViewById(R.id.last_post);
            viewHolder.postedTimeAgoView = (TextView) followedUserView.findViewById(R.id.posted_time_ago);
            viewHolder.imageView = (ImageView) followedUserView.findViewById(R.id.user_icon);
            followedUserView.setTag(viewHolder);
        }

        ViewHolder holder = (ViewHolder) followedUserView.getTag();
        holder.userNameView.setText(values.get(position).getName());
        holder.lastPostView.setText(values.get(position).getLastMicropost());
        holder.postedTimeAgoView.setText(values.get(position).getPostedTimeAgo());
        ImageView imageView = holder.imageView;
        String gravatarURL = "http://www.gravatar.com/avatar/"
                + values.get(position).getGravatarId();
        Picasso.with(context).load(gravatarURL).into(imageView);


        return followedUserView;
    }

}