Remove items from a Custom ListView (Android)

In order to create a neverending listview the first thing you need to have is a set of two runnables. These threads will update the array of data in your adapter.

final int itemsPerPage = 100;
ArrayList<HashMap<String,String>> listItems = new ArrayList<HashMap<String,String>>();
boolean loadingMore = false;
int item = 0;

//Since we cant update our UI from a thread this Runnable takes care of that!
 public Runnable returnRes = new Runnable() {

    @Override
    public void run() {
        //Loop thru the new items and add them to the adapter
        if(groceries.getGroceries().size() > 0){
                    for(int i=0;i < listItems.size();i++) {
                        HashMap<String,String> grocery = listItems.get(i);
                        adapter.add(grocery);
                    }
        //Update the Application title
                setTitle("Grocery List with " + String.valueOf(groceries.getGroceries().size()) + " items");
        //Tell to the adapter that changes have been made, this will cause the list to refresh
                    adapter.notifyDataSetChanged();
        //Done loading more.
                    loadingMore = false;
            }
    }
 };


//Runnable to load the items
public Runnable loadMoreListItems = new Runnable() {
@Override
public void run() {

    //Set flag so we cant load new items 2 at the same time
    loadingMore = true;
    //Reset the array that holds the new items
    listItems = new ArrayList<HashMap<String,String>>();
    //Get 8 new listitems
    for (int i = 0; i < itemsPerPage; i++) {
        if (i < groceries.getGroceries().size()) {
            listItems.add(groceries.getGroceries().get(i));
            item++;
        }
    }
    //Done! now continue on the UI thread
            runOnUiThread(returnRes);
}

};

Then your onCreate() method should look something like this with an array passed to your adapter:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_create_grocery_list);



    //add the footer before adding the adapter, else the footer will not load!
    View footerView = ((LayoutInflater)this.getSystemService(Context.LAYOUT_INFLATER_SERVICE))
            .inflate(R.layout.activity_footer_view, null, false);
    this.getListView().addFooterView(footerView);
    adapter = new ListViewAdapter(this,groceries);

    setListAdapter(adapter);
    getListView().setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
    //Here is where the magic happens
    this.getListView().setOnScrollListener(new OnScrollListener(){
        //useless here, skip!
        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {}
        //dumdumdum
        @Override
        public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
            //what is the bottom iten that is visible
            int lastInScreen = firstVisibleItem + visibleItemCount;
            //is the bottom item visible & not loading more already ? Load more !
            if((lastInScreen == totalItemCount) && !loadingMore && item < groceries.getGroceries().size()){
                Thread thread =  new Thread(null, loadMoreListItems);
                thread.start();
            }
        }
    });

}

You will also need a delete method to remove the items with checkboxes and a checkOff method as well. They look like this:

ArrayList<Integer> checkedBoxes = new ArrayList<Integer>();

ArrayList<HashMap<String,String>> checkedItems = new ArrayList<HashMap<String,String>>();

public void deleteItem(View view) {
      if (checkedBoxes.size() > 1 || checkedBoxes.size() == 0) {
          Toast.makeText(getApplicationContext(), "You can only delete one item at a time. Sorry :(", Toast.LENGTH_LONG).show();
          return;
      } else {

          checkedItems.add(groceries.getGroceries().get(checkedBoxes.get(0)));


          groceries.getGroceries().removeAll(checkedItems);
          checkedBoxes.clear();
          try {
              groceries.serialize();
          } catch (Exception e) {
              // TODO Auto-generated catch block
              e.printStackTrace();
          }

          Intent intent = new Intent(getApplicationContext(),CreateGroceryList.class);
          startActivity(intent);

      }
}

public void checkOff(View view) {
    CheckBox box = (CheckBox)view;
    DataModel d = (DataModel)box.getTag();
    if(!checkedBoxes.contains(d.index)) {
        checkedBoxes.add(d.index);
    } else {
        checkedBoxes.remove((Integer)d.index);
    }
}

In order to communicate with the adapter it is helpful to have a DataModel class that will model our information. My DataModel has an index variable to keep track of the selected item.

public class DataModel {
int index;
HashMap<String,String> data;
boolean selected;

public DataModel(int i) {
    index = i;
    data = new HashMap<String,String>();
    selected = false;
}

public HashMap<String, String> getData() {
    return data;
}

public void setData(HashMap<String, String> data) {
    this.data = data;
}

public boolean isSelected() {
    return selected;
}

public void setSelected(boolean selected) {
    this.selected = selected;
}

}

Finally, here is the code for the BaseAdapter:

    public class ListViewAdapter extends BaseAdapter {//To create an adapter we have to extend BaseAdapter instead of Activity, or whatever.

    private ListActivity activity;
    private View vi;
    private ArrayList<DataModel> data;
    private static LayoutInflater inflater=null;


    public ListViewAdapter(ListActivity a, GroceryList g) {
        activity = a;
        data = new ArrayList<DataModel>();
        inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        groceries = g;
    }



    public void add(HashMap<String,String> a){
        DataModel d = new DataModel(data.size());
        d.setData(a);
        d.setSelected(false);
        data.add(d);
    }

    public ArrayList<DataModel> getData() {
        return data;
    }

    public int getCount() {   //get the number of elements in the listview
        return data.size();
    }

    public Object getItem(int position) {   //this method returns on Object by position
        return position;
    }

    public long getItemId(int position) {   //get item id by position
        return position;
    }

    public View getView() {
        return vi;
    }

    public View getView(int position, View convertView, ViewGroup parent) {   //getView method is the method which populates the listview with our personalized rows
        vi=convertView;
        final ViewHolder holder = new ViewHolder();
        if(convertView==null) {
            vi = inflater.inflate(R.layout.custom_row_view, null);

        //every item in listview uses xml "listview_row"'s design 

            holder.name = (CheckBox)vi.findViewById(R.id.name);
            holder.price = (TextView)vi.findViewById(R.id.price);   // You can enter anything you want, buttons, radiobuttons, images, etc.
            holder.quantity = (TextView)vi.findViewById(R.id.quantity);
            holder.name
            .setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

                @Override
                public void onCheckedChanged(CompoundButton buttonView,
                    boolean isChecked) {
                  DataModel element = (DataModel) holder.name
                      .getTag();
                  element.setSelected(buttonView.isChecked());

                }
              });
            vi.setTag(holder);
            holder.name.setTag(data.get(position));
            ViewHolder vholder = (ViewHolder) vi.getTag();
            vholder.name.setChecked(data.get(position).isSelected());
            HashMap<String, String> hash = new HashMap<String, String>();  //We need a HashMap to store our data for any item
            hash = data.get(position).getData();
            vholder.name.setText(hash.get("brand") + " " + hash.get("name"));  //We personalize our row's items.
            vholder.price.setText("$" + hash.get("price"));
            vholder.quantity.setText("Quantity: " + hash.get("quantity"));
        } else {
            vi = convertView;
            ((ViewHolder) vi.getTag()).name.setTag(data.get(position));
        }

            if (holder.name == null) {
                ViewHolder vholder = (ViewHolder) vi.getTag();
                vholder.name.setChecked(data.get(position).isSelected());
                HashMap<String, String> hash = new HashMap<String, String>();  //We need a HashMap to store our data for any item
                hash = data.get(position).getData();
                vholder.name.setText(hash.get("brand") + " " + hash.get("name"));  //We personalize our row's items.
                vholder.price.setText("$" + hash.get("price"));
                vholder.quantity.setText("Quantity: " + hash.get("quantity"));

            }   

        return vi;  
    }
}

class ViewHolder {
    CheckBox name;
    TextView price;
    TextView quantity;
    public CheckBox getName() {
        return name;
    }
    public void setName(CheckBox name) {
        this.name = name;
    }
    public TextView getPrice() {
        return price;
    }
    public void setPrice(TextView price) {
        this.price = price;
    }
    public TextView getQuantity() {
        return quantity;
    }
    public void setQuantity(TextView quantity) {
        this.quantity = quantity;
    }

}

You also need a few xml files in your layout folder this is what they will look like:

You need a footerview that will tell your list when to load new items:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:gravity="center_horizontal"
android:padding="3dp"
android:layout_height="fill_parent">
        <TextView
               android:id="@id/android:empty"
               android:layout_width="wrap_content"
               android:layout_height="fill_parent"
               android:gravity="center"
               android:padding="5dp"
               android:text="Add more grocery items..."/>

A custom row view that is populated by your BaseAdapter:

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



    <CheckBox
        android:id="@+id/name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="CheckBox"
        android:focusable="false"
        android:textSize="25dip"
        android:onClick="checkOff"
        />

    <TextView
        android:id="@+id/quantity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="40dip"
        android:text="Lastname"
        android:textSize="15dip" />

    <TextView
        android:id="@+id/price"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="40dip"
        android:text="Lastname"
        android:textSize="15dip" />




</LinearLayout>

And a parent view, mine is called create_grocery_list because I'm writing a grocery list editor: This one must contain a ListView with the proper id.

    <?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" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="400dp" >

        <ListView
            android:id="@android:id/list"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1" >
        </ListView>

    </LinearLayout>

    <AbsoluteLayout
        android:layout_width="match_parent"
        android:layout_height="72dp" >

        <Button
            android:id="@+id/button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_x="105dp"
            android:layout_y="0dp"
            android:onClick="deleteItem"
            android:text="@string/deleteItem" />

        <Button
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_x="8dp"
            android:layout_y="0dp"
            android:onClick="goToAddItemScreen"
            android:text="@string/addItem" />

        <Button
            android:id="@+id/button3"
            style="?android:attr/buttonStyleSmall"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_x="221dp"
            android:layout_y="0dp"
            android:onClick="scanner"
            android:text="@string/scanCode" />
    </AbsoluteLayout>

</LinearLayout>

And that's about it... hope this helps anyone. It's the most complete tutorial you'll find.

I learned all this from this tutorial: http://www.vogella.com/articles/AndroidListView/article.html#androidlists_overview then added the two runnables to make a neverending grocery list :) have fun programming...