如何在片段中按下后退按钮时显示警告消息

我希望应用程序在用户按下后退按钮时显示警告消息，如果用户选择“是”，它将返回。我在导航图片段中。

我在堆栈溢出中搜索了很多次并尝试过：

@Override
public void onBackPressed() {
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

    builder.setTitle("Save Or Not");
    builder.setMessage("Do you want to save this? ");
    builder.setPositiveButton("Save", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int id) {
            /*Go back:-I dont know how*/
        }
    });
    builder.setNegativeButton("Discard",null);
    builder.show();
}

但它显示给出者错误：方法不会覆盖其超类中的方法

编辑： 我想在导航图片段中设置 onBackPressedListener(手机后退按钮)

使用 Fragments 1.1.0（目前处于 alpha 版本）时，您可以按照提供自定义后退导航文档 https://developer.android.com/guide/navigation/navigation-custom-back，它展示了如何注册OnBackPressedCallback https://developer.android.com/reference/androidx/activity/OnBackPressedCallback，这允许您注册onBackPressed()来自 Fragment 内的回调：

public class MyFragment extends Fragment {

  @Override
  public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // This callback will only be called when MyFragment is at least Started.
    OnBackPressedCallback callback = new OnBackPressedCallback(true /* enabled by default */) {
        @Override
        public void handleOnBackPressed() {
            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

            builder.setTitle("Save Or Not");
            builder.setMessage("Do you want to save this? ");
            builder.setPositiveButton("Save", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                // Save your content
                save();
                // Then pop
                NavHostFragment.findNavController(MyFragment.this).popBackStack();
            }
            builder.setNegativeButton("Discard",null);
            builder.show();
        });
        }
    });
    requireActivity().getOnBackPressedDispatcher().addCallback(this, callback);
  }
}