Question

我创建了包含动态项目的listview，其中包含两个项目：CheckBox和TextView。当用户点击项目内的复选框时，它会更新textView的背景颜色。它工作正常，直到这个项滚出列表的用户空间的可见区域，我得到错误：com.viewactivities.AddNewPosition.changeTextColorWhenCheckBoxIsClicked（AddNewPosition.java:183）的java.lang.NullPointerException。

我还使用一种负责改变颜色的方法实现了接口。我观察过方法＆＃34; changeTextColorWhenCheckBoxIsClicked＆＃34;当listView中的项目不再可见时也会被触发（这里它会导致错误）。有人可以帮忙吗？

包含listview的类的代码和更改颜色的方法：

@Override
public void changeTextColorWhenCheckBoxIsClicked(int position) {
    // TODO Auto-generated method stub

    listView.getChildAt(position).findViewById(R.id.listViewItemText).setBackgroundColor(Color.BLUE);

}

来自listView适配器的代码：

@Override
    public View getView(int position, View convertView, ViewGroup parent) 
    {
          ViewHolder viewHolder = null;
          globalPosition = position;

        if(convertView==null){

             LayoutInflater inflater =  ((AddNewPosition) mContext).getLayoutInflater();    
             convertView = inflater.inflate(layoutResourceId, parent, false);

             viewHolder = new ViewHolder();
                viewHolder.text = (TextView) convertView.findViewById(R.id.listViewItemText);
                viewHolder.checkbox = (CheckBox) convertView.findViewById(R.id.listViewItemCheckBox);

                viewHolder.checkbox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

                    @Override
                    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {


                        int getPosition = (Integer) buttonView.getTag();  // Here we get the position that we have set for the checkbox using setTag.
                        listOfObjects.get(getPosition).setCheckBoxEnabled(buttonView.isChecked()); // Set the value of checkbox to maintain its state.   changeTextColorWhenCheckBoxIsClicked(getPosition);
                    }
                });
                convertView.setTag(viewHolder);
                convertView.setTag(R.id.listViewItemText, viewHolder.text);
                convertView.setTag(R.id.listViewItemCheckBox, viewHolder.checkbox);
                } else {
                viewHolder = (ViewHolder) convertView.getTag();
            }
            viewHolder.checkbox.setTag(position); // This line is important.

            viewHolder.text.setText(listOfObjects.get(position).getTextFromListViewItemObject());
            viewHolder.checkbox.setChecked(listOfObjects.get(position).getIsCheckedBoxEnabled());
            //viewHolder.text.setBackgroundColor(Color.RED);

        //ListViewItemObject tmpObject = listOfObjects.get(position);

        //TextView listItemText = (TextView) convertView.findViewById(R.id.listViewItemText);
        //CheckBox checkBox = (CheckBox) convertView.findViewById(R.id.listViewItemCheckBox);
        //checkBox.setChecked(false);

        //listItemText.setText(tmpObject.getTextFromListViewItemObject());

         return convertView;
    }


    @Override
    public void changeTextColorWhenCheckBoxIsClicked(int position) {
        // TODO Auto-generated method stub

        ((AddNewPosition) mContext).changeTextColorWhenCheckBoxIsClicked(position);

    }

Answer 1

ListView重用其视图，因此不使用setTag（）而是使用列表来维持位置。

viewHolder.checkbox.setTag(position); // This line is important.

像这样的东西 - Android Listview Scrolling challenge for row elements

ListView项目背景颜色更新

1 个答案: