NullPointerException异常的getChildAt [英] Nullpointerexception on getChildAt

问题描述

我有一些复选框列表视图，我需要根据存储在阵列的一些数据会自动检查。扩展底座适配器我的自定义适配器：

I have a listview with some check boxes and i need to check them automatically according to some data that are stored in array. My custom adapter that extends base adapter:

 public class MyAdapter extends BaseAdapter 
    {
        private Context context;

        public SPCMjereAdapter(Context c) 
        {           
            context = c;                    
        }

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

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

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

        public int getlistItemsCount()
        {
            return listView.getChildCount();
        }

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

            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            if (convertView == null) {
                convertView = inflater.inflate(R.layout.activity_list_row, null);

            }   
            // ColID
            TextView txtOpis = (TextView) convertView.findViewById(R.id.ColOpis); 
            txtOpis.setText(MyArrList.get(position).get("OpisMjere") +".");

            // ColCode
            TextView txtRbMjere = (TextView) convertView.findViewById(R.id.ColCode);
            txtRbMjere.setText(MyArrList.get(position).get("RbMjere"));


            // ColChk               
            CheckBox Chk = (CheckBox) convertView.findViewById(R.id.ColChk);
            Chk.setTag(MyArrList.get(position).get("RbMjere"));


            return convertView;

        }

    }

和我这是怎么检查的项目

And this is how i check the items

int k=0;
    int j=0;
    for (j=0; j<numberOfItems; j++)
    {

        LinearLayout itemLayout = (LinearLayout)listView.getChildAt(j); // Find by under LinearLayout
        CheckBox checkbox = (CheckBox)itemLayout.findViewById(R.id.ColChk);

        for (k=0; k<rbmjere.size(); k++)
        {
            if (checkbox.getTag().toString() == rbmjere.get(k).toString())
            {
                checkbox.setChecked(true);
            }
        }   
    }

问题是行

LinearLayout itemLayout = (LinearLayout)listView.getChildAt(j);

所以，如果我把这个code检查项目的问题是，列表视图显示例如3个项目，但code只承认2项和第三项缺失。如何当所有项目都可见或如何在列表视图渲染完成检测检测？

So if I call this code for checking items the problem is that listview show for example 3 items but the code recognize only 2 items and third item is missing. How to detect when all items are visible or how to detect when rendering of listview is finished?

推荐答案

问题就解决了​​。内部getView（）我写这几行和它的作品只是我想：

Problem is solved. Inside getView() i wrote these few lines and it works just I wanted:

for (k=0; k<rbmjere.size(); k++)
            {
                if (Chk.getTag().toString().equals(rbmjere.get(k).toString()))
                {
                    Chk.setChecked(true);

                }
            }   

感谢所有的帮助和想法。

Thanks to all on help and ideas.

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