final EditText inputServer = new EditText(this);

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

        builder.setTitle("Server").setIcon(android.R.drawable.ic_dialog_info).setView(inputServer)

                .setNegativeButton("Cancel", null);

        builder.setPositiveButton("Ok", new DialogInterface.OnClickListener() {

            public void onClick(DialogInterface dialog, int which) {

               inputServer.getText().toString()；

             }

        });

        builder.show();

OR

见SDK自带的源代码Api Demos里的： 

App -> Dialog -> Text Entry dialog