Volley 库无法连接到服务器

Question

我试图JSONObject从数据库中检索一个，但我发现该请求甚至没有发送到服务器。我检查了Apache Access Log确认这一点。URL 有效，当我通过 Web 浏览器访问它时，它返回预期的 JSONObject。nullVolley 库显示的异常错误。

 private void GetSchInfo(){

    showDialog();

    // making fresh volley request and getting json
    JsonObjectRequest jsonReq = new JsonObjectRequest(Request.Method.GET,
            URL_SchInfo, null, new Response.Listener<JSONObject>() {

        @Override
        public void onResponse(JSONObject response) {


            try{

                spinnerClass.setVisibility(View.VISIBLE);
                spinnerSch.setVisibility(View.VISIBLE);
                spinnerDept.setVisibility(View.VISIBLE);
                btnRegClass.setVisibility(View.VISIBLE);
                txtClassMsg.setVisibility(View.VISIBLE);
                btnRefresh.setVisibility(View.GONE);

                JSONArray schools = response.getJSONArray("sch_info");
                JSONArray departments = response.getJSONArray("dept_info");

                for (int i = 0; i < schools.length(); i++){
                    JSONObject schObj = (JSONObject)schools.get(i);
                    SchInfo sch = new SchInfo(schObj.getString("school_id"), schObj.getString("school_name"));
                    schoolList.add(sch);
                }

                for (int j = 0; j < departments.length(); j++){
                    JSONObject deptObj = (JSONObject)departments.get(j);
                    DeptItem dept = new DeptItem(deptObj.getString("department_id"), deptObj.getString("department_name"));
                    deptList.add(dept);
                }


                //populate
                //populateInfo();

            }catch(JSONException e){
               Log.e(TAG, "JSON Error: " + e.getMessage());
                e.printStackTrace();
                spinnerClass.setVisibility(View.GONE);
                txtClassMsg.setVisibility(View.GONE);
                spinnerSch.setVisibility(View.GONE);
                spinnerDept.setVisibility(View.GONE);
                btnRegClass.setVisibility(View.GONE);
                btnRefresh.setVisibility(View.VISIBLE);

             }

            hideDialog();
        }
    }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
            String body;

                if (error.networkResponse.data !=null){
                try {
                    body = new String(error.networkResponse.data, "UTF-8");
                }catch (UnsupportedEncodingException e){
                    e.printStackTrace();
                }
            }

          Log.e("Error: ",   error.getCause()  +">>" + error.getMessage());
            Log.e(TAG, "JSON Error: " + error.getMessage() );
            hideDialog();
            spinnerClass.setVisibility(View.GONE);
            spinnerSch.setVisibility(View.GONE);
            spinnerDept.setVisibility(View.GONE);
            btnRegClass.setVisibility(View.GONE);
            txtClassMsg.setVisibility(View.GONE);
            btnRefresh.setVisibility(View.VISIBLE);
        }
    });

    // Adding request to volley request queue
    AppController.getInstance().addToRequestQueue(jsonReq);
}

我该如何解决这个问题？

注意 服务器在我的本地机器上，我通过热点连接类似http://192.164.***.***.

Answer 1

这可能是由于 URL 不安全，因此您可以在 AndroidManifest.xml 中添加这一行

机器人：使用CleartextTraffic =“真”

 <application
    android:name=".ExampleApp"
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher_new"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_circle"
    android:largeHeap="true"
    android:resizeableActivity="false"
    android:usesCleartextTraffic="true"
    android:screenOrientation="portrait"
    android:theme="@style/AppTheme.NoActionBar">

如果它给出了 [java.lang.NoClassDefFoundError: Failed resolution of: Lorg/apache/http/ProtocolVersion] 错误，则将此行添加为应用程序标记子项。

<uses-library android:name="org.apache.http.legacy" android:required="false"/>

欲了解更多详情，请访问此链接——

https://developer.android.com/about/versions/pie/android-9.0-changes-28#apache-p