How to prevent AlertDialog to close?

Question

I'm using AlertDialog.Builder to build my dialog, it has an EditText which is necessary to be filled and I want to prevent closing the dialog while it is not. In the positive button's onClickListener I can check if the editText is filled or not but I don't know how to prevent closing...

builder.setPositiveButton("title", new DialogInterface.OnClickListener(){
     @Override
     public void onClick(DialogInterface dialog, int which) {
           if(...){
              //can close
           }else{
            //prevent closing
           }
     }
})

Answer 1

You can change the behavior of the button immediately after calling show() of the dialog, like this.

AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setMessage("Test for preventing dialog close");
builder.setPositiveButton("Test", 
        new DialogInterface.OnClickListener()
        {
            @Override
            public void onClick(DialogInterface dialog, int which)
            {
                //Do nothing here because we override this button later to change the close behaviour. 
                //However, we still need this because on older versions of Android unless we 
                //pass a handler the button doesn't get instantiated
            }
        });
AlertDialog dialog = builder.create();
dialog.show();
//Overriding the handler immediately after show is probably a better approach than OnShowListener as described below
dialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(new View.OnClickListener()
      {            
          @Override
          public void onClick(View v)
          {
              Boolean wantToCloseDialog = false;
              //Do stuff, possibly set wantToCloseDialog to true then...
              if(wantToCloseDialog)
                  dialog.dismiss();
              //else dialog stays open. Make sure you have an obvious way to close the dialog especially if you set cancellable to false.
          }
      });