change first element in list

How I can change buttontext of the first element in listview?

 View v = getListView().getChildAt(0 - yourListView.getFirstVisiblePosition());开发者_Go百科
 Button Butt = (Button) v.findViewById(R.id.buttonLine);
 Butt.setText("newtext");

This code crashes application.

Solved.

  // A ViewHolder keeps references to children views to avoid
  // unneccessary calls
  // to findViewById() on each row.
  ViewHolder holder;

  // When convertView is not null, we can reuse it directly, there is
  // no need
  // to reinflate it. We only inflate a new View when the convertView
  // supplied
  // by ListView is null.
  if (convertView == null) {
    convertView = mInflater.inflate(R.layout.adaptor_content, null);

    // Creates a ViewHolder and store references to the two children
    // views
    // we want to bind data to.
    holder = new ViewHolder();

    holder.buttonLine = (Button) convertView.findViewById(R.id.buttonLine);
    } else {
    // Get the ViewHolder back to get fast access to the TextView
    // and the ImageView.
    holder = (ViewHolder) convertView.getTag();
  } holder.buttonLine.setText("Changed text of button"); 
  /////////////
  static class ViewHolder {
  TextView textLine;
  ImageView iconLine;
  Button buttonLine;
  TextView textTwo;

}

This code sets buttons texts one by one. You must just set some condition with if (for example if package installed set "Uninstall", and if not set "Install") . With this code I can't set "second of first element". But I can add counter and check condition.

The code that you are passing to getChildAt(...) is always going to be negative, except when the position is 0. As a result, it will generally return null according to the documentation. That null value will then crash when trying to use it with null.findViewById(...).

Try removing the

"0 -"

I think I found the answer, but you'll have to test it.

RelativeLayout listItem = (RelativeLayout)getListView().getChildAt(getListView().getFirstVisiblePosition()); 
Button btn = (Button)listItem.findViewById(R.id.buttonLine);
btn.setText("Hi! I updated you manually!");

Basically, what you're getting from getListView().getChildAt() is the RelativeLayout object, defined in your XML as list item template. Then you get item number 2 from it - the third item defined, which is your Button.