ListView and Adapter with a large number of items
<p>I am a newbie of android programming. After some study of ListView and ArrayAdapter, i decided to write a simple demo program just for practicing. </p>

<p>I want to display my custom view style ListView, so I override ArrayAdapter's getView() function. I know that for preventing memory leak, parameter convertView should be checked, and only inflate new object when convertView is null. I Also make a AsyncTask to keep adding data into ArrayAdapter in background(in doInBackground), and keep notifyDataChanged to ListView(in onProgressUpdate() ).</p>

<p>Here is the problem: when I set MAX_ITEM=50 (which means how many data i will add in AsyncTask), everything works fine. But when I set MAX_ITEM=500, logcat shows error message: <strong>"Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views."</strong> and application shut down. Can anyone tell me where the problem is? The following is my source code "MyTest.java" and my layout xml file "main.xml" and "layout_row.xml", thanks for your watching and helping.</p>

<p>MyTest.Java:</p>

<pre><code>public class MyTest extends Activity  { 

private static final String TAG="Tany";
private static final int MAX_ITEM = 50;
private MyArrayAdapter adapter;
private ListView listview;

private int addCounter = 0;

public class MyData implements Comparable&lt;MyData&gt;{

    public String str1;
    public String str2;
    public String str3;

    public MyData(String str1, String str2, String str3){                   
        this.str1 = str1;
        this.str2 = str2;
        this.str3 = str3;
    }

    @Override
    public int compareTo(MyData data) {
        // TODO Auto-generated method stub

        int result = this.str1.compareTo(data.str1);
        return result;
    }
}

public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.main);
     listview = (ListView)findViewById(R.id.listview);

     adapter = new MyArrayAdapter(this, R.layout.layout_row);

     //set adapter
     listview.setAdapter(adapter);
     listview.setOnItemClickListener(new AdapterView.OnItemClickListener(){

        @Override
        public void onItemClick(AdapterView&lt;?&gt; parent, View view, int position, long id) {
            // TODO Auto-generated method stub
            Log.d(TAG, "position "+position+" is clicked");                             
            Toast.makeText(parent.getContext(), adapter.getItem(position).str1+", "+adapter.getItem(position).str2, Toast.LENGTH_SHORT).show();                             
        }           
     });         

     listview.setTextFilterEnabled(true);

}

public void onStart(){
    super.onStart();                                
    MyTask newTask = new MyTask();
    newTask.execute();      
}

public class MyTask extends AsyncTask&lt;Void, Void, Void&gt;{

    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub
        for(int i = addCounter; i&lt;MAX_ITEM; i++)
        {
            adapter.add(new MyData("str1="+i,"str2="+i,"str3="+i));
            addCounter++;               
            publishProgress();                              
        }
        return null;
    }

    @Override
    protected void onProgressUpdate(Void... progress ){         
        adapter.notifyDataSetChanged();
    }

    @Override
    protected void onPostExecute(Void result){                      
        Log.d(TAG, "AsyncTask MyTask finsish its work");                        
    }       
}


public class MyArrayAdapter extends ArrayAdapter&lt;MyData&gt;{       

    public MyArrayAdapter(Context context, int textViewResourceId) {
        super(context, textViewResourceId);
        // TODO Auto-generated constructor stub                                     
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {         
        View row;                   
        if(convertView == null){
            LayoutInflater inflater = getLayoutInflater();
            row = inflater.inflate(R.layout.layout_row, parent, false);
        }else{
            Log.d(TAG,"recycle view, pos="+position);
            row = convertView;
        }

        TextView tv1 = (TextView) row.findViewById(R.id.textView1);         
        tv1.setText(    ((MyData)getItem(position)).str1    );

        TextView tv2 = (TextView) row.findViewById(R.id.textView2);
        tv2.setText(    ((MyData)getItem(position)).str2    );

        TextView tv3 = (TextView) row.findViewById(R.id.textView3);
        tv3.setText(    ((MyData)getItem(position)).str3    );

        return row;
    }                   
}   
}
</code></pre>

<p>main.xml:</p>

<pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/vertical_container" 
android:orientation="vertical"
android:layout_width="fill_parent" 
android:layout_height="fill_parent"&gt;

&lt;TextView 
        android:text="@string/list_title_start"             
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"&gt;
&lt;/TextView&gt;

&lt;ListView 
    android:id="@+id/listview"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"&gt;        
&lt;/ListView&gt;

&lt;TextView 
        android:text="@string/list_title_end"           
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"&gt;
&lt;/TextView&gt;
&lt;/LinearLayout&gt;
</code></pre>

<p>layout_row.xml:</p>

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

&lt;LinearLayout 
    android:layout_height="wrap_content" 
    android:layout_width="wrap_content" 
    android:id="@+id/linearLayout1" 
    android:orientation="horizontal"&gt;
    &lt;ImageView 
        android:layout_height="wrap_content"
        android:id="@+id/imageView1" 
        android:layout_width="wrap_content" 
        android:src="@drawable/ic_launcher"&gt;        
    &lt;/ImageView&gt;
    &lt;TextView 
        android:text="TextView1" 
        android:id="@+id/textView1" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_marginLeft="6dip"
        android:layout_marginTop="6dip" 
        android:textAppearance="?android:attr/textAppearanceLarge"&gt;
    &lt;/TextView&gt;
&lt;/LinearLayout&gt;
&lt;LinearLayout 
    android:layout_height="wrap_content" 
    android:layout_width="wrap_content" 
    android:id="@+id/linearLayout1" 
    android:orientation="horizontal"&gt;
    &lt;TextView 
        android:id="@+id/textView2" 
        android:text="TextView" 
        android:layout_height="wrap_content" 
        android:layout_width="wrap_content" 
        android:textAppearance="?android:attr/textAppearanceSmall"&gt;
    &lt;/TextView&gt;
    &lt;TextView 
        android:text="TextView" 
        android:id="@+id/textView3" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:textAppearance="?android:attr/textAppearanceSmall" 
        android:layout_marginLeft="6dip"&gt;
    &lt;/TextView&gt;
&lt;/LinearLayout&gt;    
&lt;/LinearLayout&gt;
</code></pre>
