以编程方式将TextView添加到Listview自定义行

Question

I want to add one TextView programatically to a Linearlayout declared in the XML file that defines a custom row which is applied to all listview rows. In order to do this I have the following code:

<LinearLayout
    android:id="@+id/zv"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignTop="@+id/title"
    android:layout_marginBottom="1dip"
    android:layout_marginLeft="5dip"
    android:layout_marginRight="5dip"
    android:orientation="vertical"
    android:padding="1dip" >
</LinearLayout>

class ListViewAdapter extends BaseAdapter {

(...)
public View getView(int position, View convertView, ViewGroup parent) {
        View vi=convertView;
        if (convertView == null)
            vi = inflater.inflate(R.layout.row, null);

        TextView tv_nz = new TextView(activity.getApplicationContext());

        LinearLayout zv = (LinearLayout)vi.findViewById(R.id.zv);

        tv_nz.setText("testing...");
        zv.addView(tv_nz);
(...)

return vi;
}

However the TextView appears more than one time in every row. What am I doing wrong? Thanks

Answer 1

What I really want to do is add a Textview in certain conditions and some ImageViews otherwise so I can't declare it in the XML file.

You should use multiple layouts to do this properly, since adding and removing Views in a row's layout can be expensive and slow. You can create the different layouts in XML or Java, but in your adapter you must override getViewTypeCount() and getItemViewType() to tell the Adapter to expect more than one layout and which layout to use for each row.

It's quite easy, I wrote an example of this in: Reusing views in Android Listview with 2 different layouts

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Original

However the TextView appears more than one time in every row. What am I doing wrong?

You have failed to account for the way ListView's recycle their rows. This is explained in great detail in Google I/O presentations like Turbo-Charge Your UI .

Perhaps you should simply add the extra TextView to your row's XML layout or use multiple layouts. It's hard to give you definitive advice since you haven't explained why you want to add the TextView.

---

This adds only one TextView to each row:

public View getView(int position, View convertView, ViewGroup parent) {
    if (convertView == null) {
        // Code here only affects new rows
        convertView = inflater.inflate(R.layout.row, null);

        TextView tv_nz = new TextView(activity.getApplicationContext());
        tv_nz.setText("testing...");
        convertView.addView(tv_nz);
    }
    else {
        // Code here affects only recycled rows
    }

    // Code here affects every row when the ListView is scrolled
    return convertView;
}

Answer 2

getView is called everytime you the OS wants to render the view. This means that every time the listview asks for the contents of the row, you are adding a new view.

If you switch to only adding the view when the convertView is not null, you'll achieve what you want.

public View getView(int position, View convertView, ViewGroup parent) {
    TextView tv_nz;

    // If the row does not exist, lets create it.
    if (convertView == null) {
        convertView = inflater.inflate(R.layout.row, null); 

        // Add the text view to the new view
        tv_nz = new TextView(activity.getApplicationContext());
        tv_nz.setId(R.id.tv_nz);

        convertView.addView(tv_nz);
    } else {
        // The row already exists, lets find the TextView
        tv_nz = (TextView) findViewById(R.id.tv_nz);
    }

    if (tv_nz != null) {
        tv_nz.setText("testing...");
    }

    return convertView;
}

By the way, you could remove the need for adding the textview dynamically by adding the textview to R.layout.row

Answer 3

You seem to add the TextView unconditionally, right?

Question is, how can you identify the single row where it must be added. Maybe by means of the position parameter? Only you know.

Answer 4

I notice that you are adding a TextView regardless of whether convertView is null or not. That may explain the fact that any one row might have multiple TextView widgets in it.

But, I do agree with the previous answers - there might be a much better method of accomplishing what you need.

Answer 5

My guess is that when the view is recycled, it already has the TextView added to it, and so when you go to add another one you're not checking to see if there is one already added from a previous view. Something like this should help:

//after your view inflation
LinearLayout zv = (LinearLayout)vi.findViewById(R.id.zv);
TextView tv_nz;
if(zv.getChildCount() == 0) {
    tv_nz = new TextView(activity.getApplicationContext());
    zv.addView(tv_nz);
} else
    tv_nz = (TextView) zv.getChildAt(0);
tv_nz.setText("testing...");

Answer 6

Here is a sample code for you. First of all, you have to decide in which format you send your data to the adapter. In my code, I sent it as an arraylist.

public class CustomArrayAdapter extends ArrayAdapter<String>
{
    ArrayList<String> list;
    Context mContext; // ADD THIS to keep a context

public CustomArrayAdapter(Context context, int textViewResourceId,
        ArrayList<String> objects)
{
    super(context, textViewResourceId, objects);
    this.mContext = context;
    // Pass the elements in the list
    list = objects;
}

Only after you have a specific data order(like the 'list') you can iterate the data row by row in the listview.

@Override
public View getView(int position, View convertView, ViewGroup parent)
{
    View row = convertView;

    if (row == null)
    {

        // get reference to the activity
        LayoutInflater inflater = ((Activity) mContext).getLayoutInflater();

        // Inflate the custom text which will replace the default text view
        //list_item is a simple lineer layout which contain textView1 in it. 
        row = inflater.inflate(R.layout.list_item, parent, false);
    }

    // Create custom text view to customize

    TextView tv = (TextView) row.findViewById(R.id.textView1);

    // TextView can be customized here or in the xml file
    tv.setText(list.get(position));

    return row;

  }
}

And finally, you can call the custom adapter like this;

 CustomArrayAdapter adapter = new CustomArrayAdapter(getActivity(),
            R.id.textView1,values);