使用Picasso在ListView Android中调色板

Question

我有一个ListView,我正在玩Palette支持库.当使用BitmapFactory.decodeStream从URL生成位图时,这会引发异常(网络在UI线程上)或可能非常昂贵.我如何使这个异步？我想不出任何有效的方法来做到这一点.什么是最好的方法？

    @Override
    public View getView(int position, View convertView, ViewGroup viewGroup) {
        final ViewHolder holder;
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.item_grid, null);
            holder = new ViewHolder();
            holder.image = (ImageView) convertView.findViewById(R.id.img_photo);
            holder.bg = (LinearLayout) convertView.findViewById(R.id.bg_title);
            holder.text = (TextView) convertView.findViewById(R.id.txt_title);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        Picasso.with(mContext)
                .load(mShows.get(position).poster)
                .into(holder.image);

        try {
            URL url = new URL(mShows.get(position).poster);
            Bitmap bitmap = BitmapFactory.decodeStream(
                    url.openConnection().getInputStream()); // Too expensive!!!
            Palette palette = Palette.generate(bitmap);

            holder.text.setText(mShows.get(position).title);
            holder.text.setTextColor(palette.getVibrantColor().getRgb());

            holder.bg.setAlpha(0.4f);
            holder.bg.setBackgroundColor(palette.getDarkMutedColor().getRgb());

        } catch (IOException e) {
            e.printStackTrace();
        }

        return convertView;
    }

Answer 1

你可以使用毕加索into(...)与Callback当图像已成功加载参数:

Picasso.with(mContext)
            .load(mShows.get(position).poster)
            .into(holder.image, new Callback() {

    @Override public void onSuccess() {
        Bitmap bitmap = ((BitmapDrawable)holder.image.getDrawable()).getBitmap();
        // do your processing here....
    }

    @Override public void onError() {
        // reset your views to default colors, etc.
    }

});