Question

Following is some test code , done to recreate a strange bug: After deleting some items from a ListView , it stops refreshing when data is invalidated. More items are deleted but list does not refresh. Even Log cat does not show debug messages for deletion. I will appreciate if any one could find out what’s wrong.

Item Layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
        android:orientation="horizontal">

    <TextView android:id="@+id/nameTextView"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              />
    <Button android:id="@+id/deleteButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Delete"
            />
</LinearLayout>

Item class:

import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class Item implements View.OnClickListener {
    private String name;
    private View itemView;
    private MyActivity owner;

    //--- getters--
    public String getName() {
        return name;
    }
    public View getView() {
        return itemView;
    }

    public Item(String n, Context c , MyActivity o)
    {
        //---store the name given--
        name = n;
        //---store reference to the owner activity--
        owner = o;

        //--- create a View for this item----
        LayoutInflater inflater = (LayoutInflater) c.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        itemView = inflater.inflate(R.layout.item,null);

        //---set up data to show--
        TextView nameTextView = (TextView) itemView.findViewById(R.id.nameTextView);
        Button deleteButton = (Button) itemView.findViewById(R.id.deleteButton);
        nameTextView.setText(name);

        //---set up events to be handled--
        deleteButton.setOnClickListener(this);

        Log.d("My_Test","Item: Hello world, my name is " + name);
    }

    //----request owner to delete this item---
    @Override
    public void onClick(View view) {
        Log.d("My_Test","Item:"+name+" requesting owner to delete me");
        owner.deleteItem(this);
    }

Activity layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
        >
<ListView android:id="@+id/myListView"
          android:layout_width="fill_parent"
          android:layout_height="fill_parent"
          />
</LinearLayout>

Activity class:

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;

public class MyActivity extends Activity {
    private ArrayList<Item> myItems;
    private ListView myListView;
    private ArrayAdapter<Item> myArrayAdapter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        //-----adapter for item list----
        //----since each item has its own view , it just returns the same---
        myArrayAdapter = new ArrayAdapter<Item>(this,0){

            @Override
            public View getView(final int position, View convertView, ViewGroup parent)      {
              Item item = getItem(position);
              Log.d("My_Test","Adapter : View for Item: " + item.getName() +"is requested." );
              return item.getView();
            }

        };

        //-----set up my list view with the adapter------
        myListView = (ListView) findViewById(R.id.myListView);
        myListView.setAdapter(myArrayAdapter);

        //------add items-------
        //----each item has its own view and a reference to this activity as their owner----
        myArrayAdapter.add(new Item("Sunday", this, this));
        myArrayAdapter.add(new Item("Monday", this, this));
        myArrayAdapter.add(new Item("Tuesday", this, this));
        myArrayAdapter.add(new Item("Wednesday", this, this));
        myArrayAdapter.add(new Item("Thursday", this, this));
        myArrayAdapter.add(new Item("Friday", this, this));
        myArrayAdapter.add(new Item("Saturday", this, this));

        myArrayAdapter.notifyDataSetChanged();

    }

    //----- called by items requesting to be deleted from the item list----
    public void deleteItem(Item item) {
        myArrayAdapter.remove(item);
        Log.d("My_Test","Owner : Deleted item :" + item.getName());
        myArrayAdapter.notifyDataSetChanged();
    }
}

Looks like ListView stops re-drawing it self. Even when List Item is no more in the item array, and myAdapter.notifyDataSetInvalidated(); is called, The List Item stays visible , with further code execution some how blocked.

Answer 1

Use an ArrayAdapter to do this. Try something like this instead…

    import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;

public class MyActivity extends Activity{
    private ListView myListView;
    private ArrayAdapter<Item> myArrayAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        myArrayAdapter = new ArrayAdapter<Item>(this,R.layout.item){    
            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                View returnedView = convertView;

                //inflate your view here
                if(returnedView == null){
                    LayoutInflater inflater = (LayoutInflater)getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                    returnedView = inflater.inflate(R.layout.item,null);
                }

                final Item item = getItem(position);

                //set the views
                if(returnedView != null){
                    TextView nameTextView = (TextView) returnedView.findViewById(R.id.nameTextView);
                    nameTextView.setText(item.getName());
                    Button deleteButton = (Button) returnedView.findViewById(R.id.deleteButton);
                    deleteButton.setOnClickListener(new OnClickListener() {
                        public void onClick(View v) {
                            remove(item);
                            notifyDataSetChanged();
                        }
                    });

                }

                return returnedView;
            }
        };

        myArrayAdapter.add(new Item("Sunday"));
        myArrayAdapter.add(new Item("Monday"));
        myArrayAdapter.add(new Item("Tuesday"));
        myArrayAdapter.add(new Item("Wednesday"));
        myArrayAdapter.add(new Item("Thursday"));
        myArrayAdapter.add(new Item("Friday"));
        myArrayAdapter.add(new Item("Saturday"));

        myListView = (ListView) findViewById(R.id.myListView);
        myListView.setAdapter(myArrayAdapter);

    }
}

public class Item{

    private String name;

    public Item(String n){
        this.name = n;
    }

    public String getName() {
        return name;
    }
}