Updating a listview (notifydatasetchange) using an interface when adapter is not in same class or package.

Struture goes like this :

1. MainActivity.this

public class MainActivity extends Activity implements Callback{

ListView mListview;

ArrayList<String>mItems;

ListviewAdapter mAdapter;



@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

intiview();

}



private void intiview() {

mListview=(ListView)findViewById(R.id.mListview);

//preparing list for items here

mItems=new ArrayList<String>();

for(int i=0;i<15;i++){

mItems.add(""+i);

}

mAdapter=new ListviewAdapter(mItems, MainActivity.this);

mListview.setAdapter(mAdapter);

}



@Override

public void onDeleteClick() {

mAdapter.notifyDataSetChanged();

}





}

2. ListviewAdapter.this

public class ListviewAdapter extends BaseAdapter {



ArrayList<String> mItems;

Context mContext;

Callback mCallback;



public ListviewAdapter(ArrayList<String> mItems, Context mContext) {

this.mContext = mContext;

this.mItems = mItems;

mCallback=(Callback) mContext;

}



@Override

public int getCount() {

return mItems.size();

}



@Override

public Object getItem(int position) {

return null;

}



@Override

public long getItemId(int position) {

return 0;

}



@SuppressLint("InflateParams")

@Override

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

View mView = convertView;

ViewHolder mHolder; // to reference the child views for later actions

if (mView == null) {

LayoutInflater mInflater = (LayoutInflater) mContext

     .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

mView = mInflater.inflate(R.layout.row_listview, null);

// cache view fields into the holder

mHolder = new ViewHolder();

mHolder.mName = (TextView) mView.findViewById(R.id.name);

mHolder.mDeletebtn = (Button) mView.findViewById(R.id.delbtn);

// associate the holder with the view for later lookup

mView.setTag(mHolder);

} else {

// view already exists, get the holder instance from the view

mHolder = (ViewHolder) mView.getTag();

}



mHolder.mName.setText(mItems.get(position));

mHolder.mDeletebtn.setOnClickListener(new OnClickListener() {



@Override

public void onClick(View v) {

     mItems.remove(position);

    mCallback.onDeleteClick();

}

});

;

return mView;

}



static class ViewHolder {

TextView mName;

Button mDeletebtn;

}



}

3.   Callback.java

public interface Callback {



void onDeleteClick();

}

XML Layouts :

1. activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent" >



    <ListView

        android:id="@+id/mListview"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content" >

    </ListView>



</RelativeLayout>

2. row_listview.xml

<?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="horizontal" >



    <TextView

        android:id="@+id/name"

        android:layout_width="0dp"

        android:layout_height="wrap_content"

        android:layout_weight=".6"

        android:padding="10dp"

        android:text="Name" />



    <Button

        android:id="@+id/delbtn"

        android:layout_width="0dp"

        android:layout_height="wrap_content"

        android:layout_weight=".4"

        android:padding="10dp"

        android:text="Delete Item" />



</LinearLayout>

Output :