java - viewholder - when getview is called in android




custom listview adapter getView method being called multiple times, and in no coherent order (7)

"Why is getview called for each row three times?" Because getView is called when you scroll on listview and to say better then that it is called when the position of an view of your list is changed!

I have a custom list adapter:

class ResultsListAdapter extends ArrayAdapter<RecordItem> {

in the overridden 'getView' method I do a print to check what position is and whether it is a convertView or not:

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        System.out.println("getView " + position + " " + convertView);

The output of this (when the list is first displayed, no user input as yet)

04-11 16:24:05.860: INFO/System.out(681): getView 0 null  
04-11 16:24:29.020: INFO/System.out(681): getView 1 [email protected]  
04-11 16:25:48.070: INFO/System.out(681): getView 2 [email protected]  
04-11 16:25:49.110: INFO/System.out(681): getView 3 [email protected]  
04-11 16:25:49.710: INFO/System.out(681): getView 0 [email protected]  
04-11 16:25:50.251: INFO/System.out(681): getView 1 null  
04-11 16:26:01.300: INFO/System.out(681): getView 2 null  
04-11 16:26:02.020: INFO/System.out(681): getView 3 null  
04-11 16:28:28.091: INFO/System.out(681): getView 0 null  
04-11 16:37:46.180: INFO/System.out(681): getView 1 [email protected]  
04-11 16:37:47.091: INFO/System.out(681): getView 2 [email protected]  
04-11 16:37:47.730: INFO/System.out(681): getView 3 [email protected]  

AFAIK, though I couldn't find it stated explicitly, getView() is only called for visible rows. Since my app starts with four visible rows at least the position numbers cycling from 0-3 makes sense. But the rest is a mess:

  • Why is getview called for each row three times?
  • Where are these convertViews coming from when I haven't scrolled yet?

I did a bit of reseach, and without getting a good answer, I did notice that people were associating this issue with layout issues. So in case, here's the layout that contains the list:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="fill_parent"
    android:layout_width="fill_parent" 
    android:orientation="vertical" >

    <TextView android:id="@+id/pageDetails"
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" />

    <ListView android:id="@+id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" 
        android:drawSelectorOnTop="false" />

</LinearLayout>

and the layout of each individual row:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="108dp"    
android:padding="4dp">

<ImageView
    android:id="@+id/thumb"        
    android:layout_width="120dp"
    android:layout_height="fill_parent"        
    android:layout_alignParentTop="true"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_marginRight="8dp"        
    android:src="@drawable/loading" />

<TextView  
    android:id="@+id/price"
    android:layout_width="wrap_content"
    android:layout_height="18dp"         
    android:layout_toRightOf="@id/thumb"
    android:layout_alignParentBottom="true"       
    android:singleLine="true" />

<TextView  
    android:id="@+id/date"
    android:layout_width="wrap_content"
    android:layout_height="18dp"         
    android:layout_alignParentBottom="true"
    android:layout_alignParentRight="true" 
    android:paddingRight="4dp"       
    android:singleLine="true" />

<TextView
    android:id="@+id/title"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:textSize="17dp" 
    android:layout_toRightOf="@id/thumb"
    android:layout_alignParentRight="true"
    android:layout_alignParentTop="true"
    android:paddingRight="4dp"   
    android:layout_alignWithParentIfMissing="true"
    android:gravity="center" />

</RelativeLayout>

Thank you for your time


For all of you who still (After setting the height of the ListView to match_parent) are stuck (like I was):

You also have to set the height of the parent layout to match_parent.

See example below. The LinearLayout is the parent here:

<LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/something" />

        <ListView
            android:id="@+id/friendsList"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </LinearLayout>

I am not able to answer your "Why" question but i definitely have a solution to the problem of the irritating "ListView items repeating" problem(if you have items in ur collection which are more than the screen height).

As many people above have mentioned, keep the android:layout_height property of the ListVew tag as fill_parent.

And about the getView() function, the solution is to use a static class called ViewHolder. Check out this example. It successfully does the task of adding all the items in ur Array or ArrayCollection.

Hope this helps friends!!

Best Regards, Siddhant


I got rid of this issue when I changed both layout_width and layout_height to match_parent (changing only layout_height didn't help).


Helpful note watch out if you have nested items. You've got to change the "highest" one to match_parent. Hope it helps someone.


Ques: Why Adapter calls getView() manytimes? Ans: As Listview renders on scrolling is refreshes it's view with next upcoming views, for which adapter needs to get views by calling getView().

Ques: Why it's calls lesser if listview width and height set to fill_parent? Ans: Because as inflator has the fixed size for the screen area for list it calculates once for rendering the views onto the screen.

Hope it will resolve your query.


This is not an issue, there is absolutely no guarantee on the order in which getView() will be called nor how many times. In your particular case you are doing the worst thing possible with a ListView by giving it a height=wrap_content. This forces ListView to measure a few children out of the adapter at layout time, to know how big it should be. This is what provides ListView with the convertViews you see passed to getView() even before you scroll.


Try with match_parent on the layout_height property of the list view. It will prevent getView() to be called so often.





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