如何在单击碎片中的后退按钮时关闭警告对话框？

public class MyFragment extends Fragment {
    // 声明警告对话框组件
    private AlertDialog alertDialog;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // 碎片的布局文件中添加一个按钮，用于触发后退操作
        View view = inflater.inflate(R.layout.fragment_layout, container, false);
        Button backButton = view.findViewById(R.id.back_button);
        backButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 显示警告对话框
                alertDialog.show();
            }
        });

        // 创建警告对话框实例
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setTitle("警告");
        builder.setMessage("确定要后退吗？");
        builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                // 关闭对话框并执行后退操作
                dialog.dismiss();
                getActivity().onBackPressed();
            }
        });
        builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                // 关闭对话框
                dialog.dismiss();
            }
        });
        alertDialog = builder.create();

        return view;
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        // 销毁警告对话框实例，释放资源
        if (alertDialog != null) {
            alertDialog.dismiss();
            alertDialog = null;
        }
    }

    @Override
    public void onBackPressed() {
        // 拦截后退按钮的默认行为，不执行后退操作
        // 可以在这里添加其他逻辑
    }
}