Prevent back button from closing a dialog box

When using DialogFragment you will need to call setCancelable() on the fragment, not the dialog:

@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    dialog = new ProgressDialog(getActivity());
    dialog.setIndeterminate(true);
    dialog.setMessage(...);
    setCancelable(false);

    return dialog;
}

Calling dialog.setCancelable() seem to have no effect. It seems that DialogFragment does not takes notice of the dialog's setting for cancelability.

To prevent the back button closes a Dialog (without depending on Activity), just the following code:

alertDialog.setOnKeyListener(new DialogInterface.OnKeyListener() {
    @Override
    public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
        // Prevent dialog close on back press button
        return keyCode == KeyEvent.KEYCODE_BACK;
    }
});

Simply use the setCancelable() feature:

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setCancelable(false);

This prevents the back button from closing the dialog, but leaves the "negative" button intact if you chose to use it.

---

While any user that does not want to accept your terms of service can push the home button, in light of Squonk's comment, here two more ways to prevent them from "backing out" of the user agreement. One is a simple "Refuse" button and the other overrides the back button in the dialog:

builder.setNegativeButton("Refuse", new OnClickListener() {
           @Override
           public void onClick(DialogInterface dialog, int which) {
               finish();
           }
       })
       .setOnKeyListener(new OnKeyListener() {
           @Override
           public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
               if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_UP)
                   finish();
               return false;
           }
       });