Java 如果条件为真，如何替换内部按钮一次点击的碎片？

如果我在下面的代码中放入if条件，则片段替换不起作用

       _doneButton.setOnClickListener(new Button.OnClickListener() {

            @Override
        public void onClick(View _view) {


          Name(no.getText().toString(), pass.getText().toString());
         if(loginsucess){


         android.support.v4.app.FragmentTransaction ft = getActivity().getSupportFragmentManager().beginTransaction();

            MainFragment mainFragment = new MainFragment();
            ft.replace(R.id.content, mainFragment);
            ft.addToBackStack(null);
            ft.commit();
    }

试试这个

if(loginsucees){
android.support.v4.app.FragmentTransaction ft = getActivity().getSupportFragmentManager().beginTransaction();

            MainFragment mainFragment = new MainFragment();
            ft.replace(R.id.content, mainFragment);
            ft.addToBackStack(null);
            ft.commit();
}
else {
//Do Nothing
}

---

条件是什么？if（loginsusees）{}检查我发布的答案为什么不将if语句添加到代码中？\u doneButton.setEnabled（loginsusees）；请解释您的答案，而不是转储代码这是不正确的方式..在只写条件ha之前不获取名称和密码？等待用户输入密码和用户名的条件是否正确？

if(loginsucees){
android.support.v4.app.FragmentTransaction ft = getActivity().getSupportFragmentManager().beginTransaction();

            MainFragment mainFragment = new MainFragment();
            ft.replace(R.id.content, mainFragment);
            ft.addToBackStack(null);
            ft.commit();
}
else {
//Do Nothing
}

_doneButton.setOnClickListener(new Button.OnClickListener() {

  @Override
     public void onClick(View _view) {
if(loginsucees){
 Name(no.getText().toString(), pass.getText().toString());
  FragmentManager manager = getSupportFragmentManager();
  FragmentTransaction ft = manager.beginTransaction();
  MainFragment mainFragment = new MainFragment();
  ft.replace(R.id.content, mainFragment,"main_fragment");
  ft.commitAllowingStateLoss();
  }
}
});