android dialog 弹不出键盘

final AlertDialog alertDialog = new AlertDialog.Builder(TrainO2OActivity.this).create();

//加上这段代码
alertDialog.setView((TrainO2OActivity.this).getLayoutInflater().inflate(R.layout.dialog_traino2o_notjoin, null));

alertDialog.show();
Window win = alertDialog.getWindow();
WindowManager.LayoutParams lp = win.getAttributes();
win.setAttributes(lp);
win.setContentView(R.layout.dialog_traino2o_notjoin);