Android : Logcat says “The specified child already has a parent. You must call removeView() on the child's parent first.” on my 2nd alert dialog

As I said in the title, I have 2 alert dialogs showing on user interaction. I have menu that has 4 options: Settings, Credits, Promocode and Exit one, but when I click on Promocode, I got an error mentioned in the question. This is my code:

switch ((int) mMergeAdapter.getItemId(position)) {
                    case 0:
                        Intent intent2 = new Intent(Browser.this,
                                SettingsActivity.class);
                        startActivity(intent2);
                        break;
                    case 1:
                        AlertDialog.Builder builder = new AlertDialog.Builder(Browser.this);
                        builder.setTitle("Credits");
                        builder.setMessage("Code\n\nTraabefi\n\nDesign\n\nSamuel 'Samael' Chmura");
                        builder.setIcon(R.drawable.holo_dark_action_info);
                        builder.setPositiveButton("OK", null);
                        AlertDialog dialog = builder.create();
                        dialog.show();
                        TextView txt = (TextView)dialog.findViewById(android.R.id.message);
                        txt.setGravity(Gravity.CENTER);
                        break;
                    case 2:
                        AlertDialog.Builder alert = new AlertDialog.Builder(Browser.this);
                        alert.setTitle("Enter your promocode.");
                        final EditText input = (EditText) findViewById(android.R.id.edit);
                        alert.setView(input);
                        alert.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int whichButton) {
                        if (input.getText().toString()=="abcd"){
                                 isPremium = true;
                        }
                        else {
                                 isPremium = false;
                        }}});
                        alert.show();
                        break;
                    case 3:
                        finish();
                }