Like Modal Dialog android

I want to get the Gender of the user before he can continue using the program, thus, I used Asyc class

 class conectNet extends AsyncTask<Void,Void,Void>

I did first to avoid using network inside main layout. and then I Show a dialogue that asks the user to Identify his gender:

protected void onPostExecute(Void result){ // this method can use UI as mentioned in its docs
...

...

the main point of my question

I make dialogue and want to stop the thread until I get user response:

 ...
    ...
     AlertDialog.Builder builder = new AlertDialog.Builder(SendRandom.this);
    builder.setTitle("gender");
     builder.setMessage(R.string.Gender_dialogQ); //Gender_dialogQ=select your gender!
    // Set up the buttons
     builder.setPositiveButton("Male", new DialogInterface.OnClickListener() { 
       @Override
       public void onClick(DialogInterface dialog, int which) {
         userGender=Gender.MALE;//put value on mainClass proprty (userGender)
    synchronized (Thread.currentThread()){
        Thread.currentThread().notify(); // here is the POINT : resume the thread when selection done
        } } });
        builder.setNegativeButton("Female", new DialogInterface.OnClickListener() {
         @Override
        public void onClick(DialogInterface dialog, int which) {
         userGender=Gender.FEMALE;
         dialog.cancel();
         synchronized (Thread.currentThread()){
        Thread.currentThread().notify();}}});
        builder.show();// show dialogue and then pause the thread by next line
         try {
        synchronized( Thread.currentThread()){
        Thread.currentThread().wait();}
                    } catch......
    ....

this make may android program to halt And close

any suggestions??