Android Listview缓存在初始化时意外工作

Question

我在listview（又称convertView）中的视图缓存有点麻烦，下面是我的代码，

private class CurrencyAdapter extends ArrayAdapter<CurrencyModel> {
    Context ctx;
    int layoutResourceId;
    List<CurrencyModel> adapter_models = null;

    public CurrencyAdapter(Context ctx, int layoutResourceId,
            List<CurrencyModel> model) {
        super(ctx, layoutResourceId, model);
        this.ctx = ctx;
        this.layoutResourceId = layoutResourceId;
        adapter_models = model;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        Log.d(Constants.APP_TAG, "position: " + position);
        View row = convertView;
        CurrencyAdapterContainer holder = null;
        if (row == null) {
            Log.d(Constants.APP_TAG, "APP NULL");
            row = ((Activity) ctx).getLayoutInflater().inflate(
                    layoutResourceId, parent, false);
            holder = new CurrencyAdapterContainer();
            holder.textView = (TextView) row
                    .findViewById(R.id.currencies_txt);
            holder.imgView = (ImageView) row
                    .findViewById(R.id.currencies_flag_icon);
            row.setTag(holder);

        } else {
            Log.d(Constants.APP_TAG, "APP NOT NULL");
            holder = (CurrencyAdapterContainer) row.getTag();
        }

        CurrencyModel curr = getItem(position);

        if (curr.currency_value == null) {
            if (counter < MAX_COUNTER) {
                ++counter;
                CurrencyJsonDownloader cDownloader = new CurrencyJsonDownloader(
                        curr, holder.textView);  //download currency value in background, and set textview text if currency_value has been loaded in onpostExcecute (i'm using AsyncTask)
                String url = CURRENCY_URL.replace("<symbol>", curr.symbol);
                Log.d(Constants.APP_TAG, "Url currency: " + url);
                cDownloader.execute(url);
            }
            holder.textView.setText("");
        } else {
            holder.textView.setText(curr.currency_value);
        }
        holder.imgView.setImageResource(curr.drawableId);

        return row;
    }

    @Override
    public CurrencyModel getItem(int position) {
        // TODO Auto-generated method stub
        return adapter_models.get(position);
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return adapter_models.size();
    }
}

static class CurrencyAdapterContainer {
    ImageView imgView;
    TextView textView;
}

这是我日志中的输出

位置：0应用程序空

位置：1应用程序不为空

位置：2个APP Not NULL

位置：3应用程序不为空

. . .

位置：10应用程序不为空

这会造成灾难，因为这意味着在后台作业中传递的textview是相同的textview，而更改的视图是相同的textview，而另一个textview将具有空白视图，除非我滚动它，当然，这会再次调用getView（），一切正常。但启动应用程序时会出现问题，因为只有一个文本视图总是在改变其值。

那么为什么会发生这种情况呢？有什么我可以做的黑客吗？？谢谢之前...

Answer 1

我认为问题在于你的列表适配器。在这里，我发布了一个适配器类，我认为它将帮助您。

public class UploadListAdaptor extends BaseAdapter {
private Context context;
private List<UploadDetailsObj> uploadList;

public UploadListAdaptor(Context context, List<UploadDetailsObj> list) {
    this.context = context;
    uploadList = list;

}

public int getCount() {
    return uploadList.size();
}

public Object getItem(int position) {
    return uploadList.get(position);
}

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

/** LIST CATEGORY */

public View getView(int position, View convertView, ViewGroup viewGroup) {

    final UploadDetailsObj chlListObj = uploadList.get(position);

    if (convertView == null) {

        LayoutInflater inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater
                .inflate(R.layout.inflator_progress_bar, null);

        TextView photoName = (TextView) convertView
            .findViewById(R.id.tv_photoname);

        Button btnProgress=(Button)convertView.findViewById(R.id.btn_progress);
    photoName.setText(chlListObj.getPhotoName());




    }


    return convertView;

}

   }

您可以使用以下代码调用此适配器。

 List<UploadDetailsObj> listofUploads= new ArrayList<UploadDetailsObj>();
 UploadListAdaptor uploadListAdptr = new UploadListAdaptor(yourclass.this,
            listofUploads);

    uploadListView.setAdapter(uploadListAdptr);

Answer 2

ListView项目视图是循环使用的，所以不要持有对特定项目视图的引用，并期望它在滚动ListView后表示相同的数据。

将数据项传递给工作任务，并让它更新数据。

更新：

• 如果您当前的项目不在屏幕上，它将从适配器请求（当ListView滚动到它时），并将显示更新的数据