我想使用片段进行登录，但在使用Stringrequest时遇到问题

<uses-permission android:name="android.permission.INTERNET" />

RequestQueue queue = Volley.newRequestQueue(getActivity());
String url = "http://example.com/login";
StringRequest stringRequest = new StringRequest(Request.Method.POST, url,
        new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                // 处理登录成功的响应
            }
        },
        new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                // 处理登录失败的响应
            }
        }) {
    @Override
    protected Map<String, String> getParams() {
        Map<String, String> params = new HashMap<>();
        params.put("username", "your_username");
        params.put("password", "your_password");
        return params;
    }
};
queue.add(stringRequest);