ListView with AlertDialog Validation

How can I apply validation to a ListView using an AlertDialog? My scenario is this, I need to have the user select the State from which they are doing a search from. The values of the State are defined in a spinner. If the user clicks on a Listview item without selecting a state I have defined an AlertDialog below.

The problem I am encountering is that the alert box displays but does not stop the execution of the underlying task.

How can I stop the execution of my AsyncTask until the user 开发者_如何转开发has selected a State from the spinner? Are there any examples showing how to validate that the user has made a selection from a spinner prior to kicking off an AsyncTask?

list.setOnItemClickListener(new OnItemClickListener() {

            public void onItemClick(AdapterView<?> parent, View itemClicked, int position, long id) {

                // This code executes just fine but runs asynchronous with my SearchProducts task.
                String selectedState = spinner.getSelectedItem().toString();
                if(selectedState.equals("Choose Your State")) {
                    alertbox("State", "Please Choose Your State");
                }           

                String strText = items[position];

                if (strText.equalsIgnoreCase(getResources().getString(R.string.menu_search))) {
                    new SearchProducts().execute();

This is my AlertDialog code.

protected void alertbox(String title, String mymessage) {
        new AlertDialog.Builder(this)
           .setMessage(mymessage)
           .setTitle(title)
           .setCancelable(true)
           .setNegativeButton(android.R.string.cancel,
              new DialogInterface.OnClickListener() {
              public void onClick(DialogInterface dialog, int whichButton){}
              })
           .show();
        }

I feel like such an amateur, I have implemented the dialog in the correct manner. What I was missing from my code was a "return" statement on my onClick for the AlertDialog. The updated code looks like this.

protected void alertbox(String title, String mymessage) { 
        new AlertDialog.Builder(this) 
           .setMessage(mymessage) 
           .setTitle(title) 
           .setCancelable(true) 
           .setNegativeButton(android.R.string.cancel, 
              new DialogInterface.OnClickListener() { 
              public void onClick(DialogInterface dialog, int whichButton){
                  return;
              } 
              }) 
           .show(); 
        }