使用Volley進行Android Studio JSON解析：獲取NullPointerException

Question

我一直在學習Volley庫解析JSON的基礎知識，我嘗試通過放置兩個參數來使用JSON對象解析進行登錄，但是最終得到了NullPointerException，這是我的代碼：

public class MainActivity extends Activity {

    // json object response url
    private String urlJsonObj = "agendamaid.com/api/v1/login";

    // json array response url
    private String urlJsonArry = "http://api.androidhive.info/volley/person_array.json";

    private static String TAG = MainActivity.class.getSimpleName();
    private Button btnMakeObjectRequest, btnMakeArrayRequest;

    // Progress dialog
    private ProgressDialog pDialog;

    private TextView txtResponse;

    // temporary string to show the parsed response
    private String jsonResponse;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btnMakeObjectRequest = (Button) findViewById(R.id.btnObjRequest);
        btnMakeArrayRequest = (Button) findViewById(R.id.btnArrayRequest);
        txtResponse = (TextView) findViewById(R.id.txtResponse);

        pDialog = new ProgressDialog(this);
        pDialog.setMessage("Please wait...");
        pDialog.setCancelable(false);

        btnMakeObjectRequest.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // making json object request
                makeJsonObjectRequest();
            }
        });

        btnMakeArrayRequest.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // making json array request
                makeJsonArrayRequest();
            }
        });

    }

    /**
     * Method to make json object request where json response starts wtih {
     * */
    private void makeJsonObjectRequest() {

        showpDialog();

        JsonObjectRequest jsonObjReq = new JsonObjectRequest(Method.POST,
                urlJsonObj, null, new Response.Listener<JSONObject>() {

            @Override
            public void onResponse(JSONObject response) {
                Log.d(TAG, response.toString());

                try {
                    // Parsing json object response
                    // response will be a json object
                    JSONObject payload = response.getJSONObject("payload");
                    String key = payload.getString("key");
                    String userID= payload.getString("userID");


                    jsonResponse = "";

                    jsonResponse += "Key: " + key + "\n\n";
                    jsonResponse += "userID: " + userID + "\n\n";


                    txtResponse.setText(jsonResponse);

                } catch (JSONException e) {
                    e.printStackTrace();
                    Toast.makeText(getApplicationContext(),
                            "Error: " + e.getMessage(),
                            Toast.LENGTH_LONG).show();
                }
                hidepDialog();
            }
        }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d(TAG, "Error: " + error.getMessage());
                Toast.makeText(getApplicationContext(),
                        error.getMessage(), Toast.LENGTH_SHORT).show();
                // hide the progress dialog
                hidepDialog();
            }
        }){

            @Override
            protected Map<String, String> getParams() {
                Map<String, String> params = new HashMap<String, String>();
                params.put("email", "aldi@gmail.com");
                params.put("password", "testingpassword");


                return params;
            }

        };

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

    /**
     * Method to make json array request where response starts with [
     * */
    private void makeJsonArrayRequest() {

        showpDialog();

        JsonArrayRequest req = new JsonArrayRequest(urlJsonArry,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        Log.d(TAG, response.toString());

                        try {
                            // Parsing json array response
                            // loop through each json object
                            jsonResponse = "";
                            for (int i = 0; i < response.length(); i++) {

                                JSONObject person = (JSONObject) response
                                        .get(i);

                                String name = person.getString("name");
                                String email = person.getString("email");
                                JSONObject phone = person
                                        .getJSONObject("phone");
                                String home = phone.getString("home");
                                String mobile = phone.getString("mobile");

                                jsonResponse += "Name: " + name + "\n\n";
                                jsonResponse += "Email: " + email + "\n\n";
                                jsonResponse += "Home: " + home + "\n\n";
                                jsonResponse += "Mobile: " + mobile + "\n\n\n";

                            }

                            txtResponse.setText(jsonResponse);

                        } catch (JSONException e) {
                            e.printStackTrace();
                            Toast.makeText(getApplicationContext(),
                                    "Error: " + e.getMessage(),
                                    Toast.LENGTH_LONG).show();
                        }

                        hidepDialog();
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d(TAG, "Error: " + error.getMessage());
                Toast.makeText(getApplicationContext(),
                        error.getMessage(), Toast.LENGTH_SHORT).show();
                hidepDialog();
            }
        });

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

    private void showpDialog() {
        if (!pDialog.isShowing())
            pDialog.show();
    }

    private void hidepDialog() {
        if (pDialog.isShowing())
            pDialog.dismiss();
    }

這是我得到的錯誤：

> 10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime: FATAL EXCEPTION: main
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime: java.lang.NullPointerException
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at com.android.volley.Request.<init>(Request.java:136)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at com.android.volley.toolbox.JsonRequest.<init>(JsonRequest.java:58)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at com.android.volley.toolbox.JsonObjectRequest.<init>(JsonObjectRequest.java:47)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at vin.cobavolley.MainActivity$5.<init>(MainActivity.java:129)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at vin.cobavolley.MainActivity.makeJsonObjectRequest(MainActivity.java:88)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at vin.cobavolley.MainActivity.access$000(MainActivity.java:29)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at vin.cobavolley.MainActivity$1.onClick(MainActivity.java:66)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at android.view.View.performClick(View.java:4204)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at android.view.View$PerformClick.run(View.java:17355)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at android.os.Handler.handleCallback(Handler.java:725)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:92)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5041)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
10-18 02:38:49.637 4154-4154/vin.cobavolley E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
10-18 02:43:49.673 4154-4154/? I/Process: Sending signal. PID: 4154 SIG: 9

請幫忙！ 先感謝您！

Answer 1

好的，對不起，給您帶來的麻煩...所有的事情都發生了，因為我沒有在網址中添加“ http：//”，現在可以正常工作了