android - Volley 库中 StringRequest 中的 NullPointer 异常

Question

我正在使用以下代码在我服务器上的 sql 数据库中注册用户。

package com.cc.envoycc.activity;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.cc.envoycc.R;
import com.cc.envoycc.app.AppConfig;
import com.cc.envoycc.app.AppController;
import com.cc.envoycc.helper.SQLiteHandler;
import com.cc.envoycc.helper.SessionManager;

import org.json.JSONException;
import org.json.JSONObject;

import java.util.HashMap;
import java.util.Map;

/**
 * Created by Harsh Ohri on 2/27/2016.
 */
public class RegisterActivity extends Activity {

    private static final String TAG = RegisterActivity.class.getSimpleName();
    private Button btnRegister;
    private Button btnLinkToLogin;
    private EditText inputFullName;
    private EditText inputEmail;
    private EditText inputPassword;
    private SQLiteHandler db;
    private SessionManager session;
    private ProgressDialog pDialog;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register);

        btnRegister = (Button) findViewById(R.id.btnRegister);
        btnLinkToLogin = (Button) findViewById(R.id.btnLinkToLogin);
        inputFullName = (EditText) findViewById(R.id.name);
        inputEmail = (EditText) findViewById(R.id.email);
        inputPassword = (EditText) findViewById(R.id.password);

        pDialog = new ProgressDialog(this);
        pDialog.setCancelable(false);

        session = new SessionManager(getApplicationContext());
        db = new SQLiteHandler(getApplicationContext());

        if (session.isLoggedIn()) {
            Intent intent = new Intent(RegisterActivity.this, MainActivity.class);
            startActivity(intent);
            finish();
        }

        btnRegister.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = inputFullName.getText().toString();
                String email = inputEmail.getText().toString();
                String password = inputPassword.getText().toString();

                if (!name.isEmpty() && !email.isEmpty() && !password.isEmpty()) {
                    registerUser(name, email, password);
                } else {
                    Toast.makeText(getApplicationContext(), "Please enter the credentials", Toast.LENGTH_LONG).show();
                }
            }
        });

        btnLinkToLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
                startActivity(intent);
                finish();
            }
        });
    }

    private void registerUser(final String name, final String email, final String password) {
        String tag_string_req = "req_register";
        pDialog.setMessage("Registering....");
        showDialog();

        StringRequest strReq = new StringRequest(Request.Method.POST, AppConfig.URL_REGISTER,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        Log.d(TAG, "Register response :" + response.toString());
                        hideDialog();
                        try {
                            JSONObject jObj = new JSONObject(response);
                            boolean error = jObj.getBoolean("error");
                            if (!error) {
                                String uid = jObj.getString("uid");
                                JSONObject user = jObj.getJSONObject("user");
                                String name = user.getString("user");
                                String email = user.getString("email");
                                String created_at = user.getString("created_at");

                                db.addUser(name, email, uid, created_at);

                                Toast.makeText(getApplicationContext(), "User successfully registered.PLease login now", Toast.LENGTH_LONG).show();

                                Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
                                startActivity(intent);
                                finish();

                            } else {
                                String errorMsg = jObj.getString("error_msg");
                                Toast.makeText(getApplicationContext(),
                                        errorMsg, Toast.LENGTH_LONG).show();
                            }
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.e(TAG, "Response error:" + error.getMessage());
                Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_LONG).show();
                hideDialog();
            }
        }) {
            @Override
            protected Map<String, String> getParams() {
                Map<String, String> params = new HashMap<String, String>();
                params.put("name", name);
                params.put("email", email);
                params.put("password", password);
                return params;
            }
        };
        AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
    }

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

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

单击注册按钮时出现空指针异常请帮助我是第一次使用 volley 库

这是日志

`

java.lang.NullPointerException                                                                  at com.android.volley.Request.<init>(Request.java:136)                                                                  at com.android.volley.toolbox.StringRequest.<init>(StringRequest.java:43)                                                                  at com.cc.envoycc.activity.RegisterActivity$5.<init>(RegisterActivity.java:137)                                                                  at com.cc.envoycc.activity.RegisterActivity.registerUser(RegisterActivity.java:97)
at com.cc.envoycc.activity.RegisterActivity.access$300(RegisterActivity.java:32)
at com.cc.envoycc.activity.RegisterActivity$1.onClick(RegisterActivity.java:75)
at android.view.View.performClick(View.java:4191)
at android.view.View$PerformClick.run(View.java:17229)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4960)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
at dalvik.system.NativeStart.main(Native Method)

`

Answer 1

在注册按钮的 if 条件中检查是否为 null。姓名、电子邮件或密码为空

 btnRegister.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String name = inputFullName.getText().toString();
            String email = inputEmail.getText().toString();
            String password = inputPassword.getText().toString();

            //Check for null here. Either name, email or password is null
            if (!name.isEmpty() && !email.isEmpty() && !password.isEmpty()) {
                registerUser(name, email, password);
            } else {
                Toast.makeText(getApplicationContext(), "Please enter the credentials", Toast.LENGTH_LONG).show();
            }
        }
    });