Android: xml layout for a listview with different items

Question

I'm reading this tutorial http://android.amberfog.com/?p=296 . I'd like to create a Listview weith different types of rows. I understand how to create the adapter, but what about the xml layout? So I definire an xml layout like this one:

<ListView/>

<TextView android:id="@+id/id1" />

<TextView android:id="@+id/id2" />

<ImageView android:id="@+id/id3" />

<TextView android:id="@+id/id4" />

Will it be a problem (for performance) if maybe one row uses just some elements (only some textviews) of the layout and another row maybe uses other elements? I don't understand if mine is the right way to define the xml or if I have to create different layout for each type of row.

Thank you in advance

EDIT: now I'm having a null point exception.

java code from the adapter:

@Override

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

ViewHolder holder = null;
int type = getItemViewType(position);

if (convertView == null) {
    holder = new ViewHolder();

    convertView = mInflater.inflate(R.layout.listview_main, null);
    holder.textView_title = (TextView)convertView.findViewById(R.id.listview1);

    convertView.setTag(holder);
} else {
    holder = (ViewHolder)convertView.getTag();
}

**holder.textView_title.setText("aaaa");** //NULL POINT EXCEPTION HERE

return convertView;

}

class ViewHolder {
    public TextView textView_title;
}

xml 1:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:id="@+id/main_layout"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="vertical"
              android:gravity="left"
              android:layout_margin="0dp">

    <!-- android:background="#0094ff" -->

    <ListView
            android:id="@id/android:list"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:fastScrollEnabled="true"
            android:scrollbarStyle="insideInset"
            android:textFilterEnabled="false"
            android:divider="@null"
            android:layout_margin="0dp"
            android:paddingTop="0dp"
            android:paddingBottom="0dp"
            android:paddingLeft="15dp"
            android:paddingRight="22dp"/>



</LinearLayout>

xml2

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="left"
    android:layout_margin="0dp">

    <TextView
        android:id="@+id/listview1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingTop="7dp"
        android:paddingBottom="0dp"
        android:paddingLeft="0dp"
        android:paddingRight="0dp"
        android:textSize="18sp"
        android:textColor="#000000"
        android:lines="1">
    </TextView>

</LinearLayout>

Answer 1

You need to override getViewItemType and getViewTypeCount. You will also need to have custom layouts.

getItemViewType(int position) - returns information which layout type you should use based on position.

You should have a look at the video in the link.

http://www.youtube.com/watch?v=wDBM6wVEO70

private static final int TYPE_ITEM1 = 0;
private static final int TYPE_ITEM2 = 1;
private static final int TYPE_ITEM3 = 2; 

Then

int type;
@Override
public int getItemViewType(int position) {

    if (position== 0){
        type = TYPE_ITEM1;
    } else if  (position == 1){
        type = TYPE_ITEM2;
    }
    else
    {
         type= TYPE_ITEM3 ;
    }
    return type;
}

 @Override
 public int getViewTypeCount() {
        return 3; 
 }
@Override  
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
LayoutInflater inflater = null;
int type = getItemViewType(position);
  // instead of if else you can use a case
   if (row  == null) {
    if (type == FIRST_TYPE) {
            //infalte layout of type1
      }
    if (type == SECOND_TYPE) {
            //infalte layout of type2
    }  else {
            //infalte layout of normaltype
 }
} 

Answer 2

• I have just solved this problem of creating different layouts for different rows.
  1. Define all the different layouts in their corresponding different xml files.
  2. Override getViewTypeCount() method and return number of defined layouts from this.
  3. Override getItemViewType() method and according to the relation between the 'position' of the element in the listview and the proposed xml layout define the condition and return the appropriate integer values.
  4. By calling the getItemViewType() method in the getView() method, we can get the number corresponding to layout, then inflate the convertView with the corresponding xml layout. And then by using findViewById(), you can get the values into objects of the TextView class defined in ViewHolder class and setText or whatever operation you want to use you can do further. As simple as it is. Suppose we have 4 types of layouts and 4 xml files named as element1, element2, element3, element4 and two common textview id as text1, text2.

@Override public int getItemViewType(int position) { if (position % 4 == 0) { return 0; } else if (position % 4 == 1) { return 1; } else if (position % 4 == 2) { return 2; } return 3; }

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

    ViewHolder holder = null;

    int type = getItemViewType(position);
    if (convertView == null) {
        switch (type) {
        case 0: {
            convertView = mInflater.inflate(R.layout.element1, null);
            break;
        }
        case 1: {
            convertView = mInflater.inflate(R.layout.element2, null);
            break;
        }
        case 2: {
            convertView = mInflater.inflate(R.layout.element3, null);
            break;
        }
        case 3: {
            convertView = mInflater.inflate(R.layout.element4, null);
            break;
        }
        }
        holder = new ViewHolder();
        holder.txt1 = (TextView) convertView.findViewById(R.id.text1);
        holder.txt2 = (TextView) convertView.findViewById(R.id.text2);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }
    String rowItem = null;
    rowItem = rowItems[position];
    holder.txt1.setText(rowItem);
    rowItem = rowItems[position+1];
    holder.txt1.setText(rowItem);
    return convertView;
}



private class ViewHolder {
    TextView txt1, txt2;
}