Android prevent a dialog from closing when a button is clicked

 My problem was that when a user clicks the Sign Up for example button I wanted to validate a field if it contains a valid email and after that dismiss or keep the dialog showing.

To achieve that I just copied the code from here which overrides the click of the buttons:

http://stackoverflow.com/questions/2620444/how-to-prevent-a-dialog-from-closing-when-a-button-is-clicked

final AlertDialog d = new AlertDialog.Builder(context)
        .setView(v)
        .setTitle(R.string.my_title)
        .setPositiveButton(android.R.string.ok, null) //Set to null. We override the onclick
        .setNegativeButton(android.R.string.cancel, null)
        .create();

d.setOnShowListener(new DialogInterface.OnShowListener() {

    @Override
    public void onShow(DialogInterface dialog) {

        Button b = d.getButton(AlertDialog.BUTTON_POSITIVE);
        b.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                // TODO Do something

                //Dismiss once everything is OK.
                d.dismiss();
            }
        });
    }