Question

我尝试从网络上加载图片（以及一些不在网络上的文字）并将其显示在listview中。问题是，listview搞砸了。有些单元格正在快速切换，并且会导致listView顺序混乱。

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        View itemView = convertView;
        if (itemView == null)
            itemView = getLayoutInflater().inflate(R.layout.coin_layout, parent, false);
        //find the coin to work with.
        Coin currentCoin = coins.get(position);

        //fill the view
        try {
            //   ImageView coinIcon = (ImageView) itemView.findViewById(R.id.coinIcon);
            //   coinIcon.setTag(currentCoin.getImageLink());

            ViewHolder holder = new ViewHolder();

            holder.position = position;
            holder.coinIcon = (ImageView) itemView.findViewById(R.id.coinIcon);
            holder.coinName = (TextView) itemView.findViewById(R.id.coinName);
            holder.coinPrice = (TextView) itemView.findViewById(R.id.coinPrice);
            holder.coinPercentage = (TextView) itemView.findViewById(R.id.coinPercentage);
            holder.currentCoin = currentCoin;


            //  holder.coinIcon = (ImageView) itemView.findViewById(R.id.coinIcon);

            // Using an AsyncTask to load the slow images in a background thread
            new AsyncTask<ViewHolder, Void, Bitmap>() {
                private ViewHolder v;
                @Override
                protected Bitmap doInBackground(ViewHolder... params) {
                    v = params[0];
                    Log.d("V log", v.currentCoin.getName());

                    Bitmap bmp = null;
                    try{
                        URL ulrn = new URL(v.currentCoin.getImageLink());
                        HttpURLConnection con = (HttpURLConnection)ulrn.openConnection();
                        InputStream is = con.getInputStream();
                        bmp = BitmapFactory.decodeStream(is);

                        if (null != bmp)
                            return bmp;
                    }
                    catch(Exception e){}
                    return bmp;
                }

                @Override
                protected void onPostExecute(Bitmap result) {
                    super.onPostExecute(result);
                    if (v.position == position) {
                        Log.d("V Posion ", "" + v.position);
                        // If this item hasn't been recycled already, hide the
                        // progress and set and show the image
                        //   v.progress.setVisibility(View.GONE);
                        v.coinIcon.setVisibility(View.VISIBLE);
                        v.coinIcon.setImageBitmap(result);

                        v.typeFace = Typeface.createFromAsset(getAssets(), "arial.ttf");
                        v.coinName.setText(v.currentCoin.getName());
                        v.coinPrice.setText("" + v.currentCoin.getPrice());
                        v.coinPercentage.setText(v.currentCoin.getPercentage());
                    }
                }
            }.execute(holder);
        } catch (NullPointerException e) {
            e.printStackTrace();
        }
        return itemView;
    }

Answer 1

首先，将为每个列表项调用getView()，并且每次都在分配ViewHolder()，无论您是否可以重用已创建的ViewHolder()。此外，我将反对AsyncTask()内的getView()而不是你可以使用Android-Universal-Image-Loader库在listView上延迟加载图像，这是非常受欢迎并定期更新。

public View getView(int position, View convertView, ViewGroup parent) {
        View itemView = convertView;
        ViewHolder holder = null;
    if (itemView == null){
        itemView = getLayoutInflater().inflate(R.layout.coin_layout, parent, false);
        holder = new ViewHolder();
    }
        Coin currentCoin = coins.get(position);
    try {
        holder.position = position;
        //... rest of the code



        //... rest of the code
        return convertView;
    }

}

Answer 2

您不应该在每个getView上创建asyncTasks。您看到的是在重复使用视图或以随机顺序完成加载后图像的结果。查看ThreadPoolExecutor服务。

getView使滚动不平滑

2 个答案: