I was following this tutorial (http://www.androidhive.info/2012/01/android-login-and-registration-with-php-mysql-and-sqlite/) to create a user login and registration for an application using volly. Everything works fine when I make it a stand alone app with no other features. The issue starts when I try integrate it with another application.
I am copying the classes produced from the tutorial straight into an existing project but I am getting a null pointer. Now before I go any further, I know what a null pointer is and I know how to solve them.
I am new-ish to Android and I am having trouble finding this one and would greatly appreciate some help with it rather then people just directing me to here -What is a NullPointerException, and how do I fix it? - as I have already looked at this but it still doesnt help me locate this error.
Login 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.Method;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.HashMap;
import java.util.Map;
import com.example.rory.pocketchef.R;
import com.example.rory.pocketchef.app.AppConfig;
import com.example.rory.pocketchef.app.AppController;
import com.example.rory.pocketchef.helper.SQLiteHandler;
import com.example.rory.pocketchef.helper.SessionManager;
public class LoginActivity extends Activity {
private static final String TAG = RegisterActivity.class.getSimpleName();
private Button btnLogin;
private Button btnLinkToRegister;
private EditText inputEmail;
private EditText inputPassword;
private ProgressDialog pDialog;
private SessionManager session;
private SQLiteHandler db;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
inputEmail = (EditText) findViewById(R.id.email);
inputPassword = (EditText) findViewById(R.id.password);
btnLogin = (Button) findViewById(R.id.btnLogin);
btnLinkToRegister = (Button) findViewById(R.id.btnLinkToRegisterScreen);
// Progress dialog
pDialog = new ProgressDialog(this);
pDialog.setCancelable(false);
// SQLite database handler
db = new SQLiteHandler(getApplicationContext());
// Session manager
session = new SessionManager(getApplicationContext());
// Check if user is already logged in or not
if (session.isLoggedIn()) {
// User is already logged in. Take him to main activity
Intent intent = new Intent(LoginActivity.this, FirstActivity.class);
startActivity(intent);
finish();
}
// Login button Click Event
btnLogin.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
String email = inputEmail.getText().toString().trim();
String password = inputPassword.getText().toString().trim();
// Check for empty data in the form
if (!email.isEmpty() && !password.isEmpty()) {
// login user
checkLogin(email, password);
} else {
// Prompt user to enter credentials
Toast.makeText(getApplicationContext(),
"Please enter the credentials!", Toast.LENGTH_LONG)
.show();
}
}
});
// Link to Register Screen
btnLinkToRegister.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent i = new Intent(getApplicationContext(),
RegisterActivity.class);
startActivity(i);
finish();
}
});
}
/**
* function to verify login details in mysql db
* */
private void checkLogin(final String email, final String password) {
// Tag used to cancel the request
String tag_string_req = "req_login";
pDialog.setMessage("Logging in ...");
showDialog();
StringRequest strReq = new StringRequest(Method.POST,
AppConfig.URL_LOGIN, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Log.d(TAG, "Login Response: " + response.toString());
hideDialog();
try {
JSONObject jObj = new JSONObject(response);
boolean error = jObj.getBoolean("error");
// Check for error node in json
if (!error) {
// user successfully logged in
// Create login session
session.setLogin(true);
// Now store the user in SQLite
String uid = jObj.getString("uid");
JSONObject user = jObj.getJSONObject("user");
String name = user.getString("name");
String email = user.getString("email");
String created_at = user
.getString("created_at");
// Inserting row in users table
db.addUser(name, email, uid, created_at);
// Launch main activity
Intent intent = new Intent(LoginActivity.this, FirstActivity.class);
startActivity(intent);
finish();
} else {
// Error in login. Get the error message
String errorMsg = jObj.getString("error_msg");
Toast.makeText(getApplicationContext(),
errorMsg, Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
// JSON error
e.printStackTrace();
Toast.makeText(getApplicationContext(), "Json error: " + e.getMessage(), Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.e(TAG, "Login Error: " + error.getMessage());
Toast.makeText(getApplicationContext(),
error.getMessage(), Toast.LENGTH_LONG).show();
hideDialog();
}
}) {
@Override
protected Map<String, String> getParams() {
// Posting parameters to login url
Map<String, String> params = new HashMap<String, String>();
params.put("email", email);
params.put("password", password);
return params;
}
};
// Adding request to request queue
AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}
private void showDialog() {
if (!pDialog.isShowing())
pDialog.show();
}
private void hideDialog() {
if (pDialog.isShowing())
pDialog.dismiss();
}
}
AppController
import android.app.Application;
import android.text.TextUtils;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.Volley;
public class AppController extends Application {
public static final String TAG = AppController.class.getSimpleName();
private RequestQueue mRequestQueue;
private static AppController mInstance;
@Override
public void onCreate() {
super.onCreate();
mInstance = this;
}
public static synchronized AppController getInstance() {
return mInstance;
}
public RequestQueue getRequestQueue() {
if (mRequestQueue == null) {
mRequestQueue = Volley.newRequestQueue(getApplicationContext());
}
return mRequestQueue;
}
public <T> void addToRequestQueue(Request<T> req, String tag) {
req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
getRequestQueue().add(req);
}
public <T> void addToRequestQueue(Request<T> req) {
req.setTag(TAG);
getRequestQueue().add(req);
}
public void cancelPendingRequests(Object tag) {
if (mRequestQueue != null) {
mRequestQueue.cancelAll(tag);
}
}
}
Android Manifest
<uses-permission android:name="android.permission.INTERNET" />
<android:uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<android:uses-permission android:name="android.permission.READ_PHONE_STATE" />
<android:uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_logo"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/MyMaterialTheme" >
<activity
android:name=".activity.LoginActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".SingleRecipeDisplay"
android:label="@string/title_activity_single_recipe_display"
android:theme="@style/MyMaterialTheme" >
</activity>
<activity android:name=".Favourites" >
</activity>
<activity android:name=".Help" >
</activity>
<activity android:name=".activity.RegisterActivity">
</activity>
</application>
Error
java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.rory.pocketchef.app.AppController.addToRequestQueue(com.android.volley.Request, java.lang.String)' on a null object reference 02-22 15:03:54.296 13823-13823/com.example.rory.pocketchef E/AndroidRuntime: at com.example.rory.pocketchef.activity.LoginActivity.checkLogin(LoginActivity.java:183) 02-22 15:03:54.296 13823-13823/com.example.rory.pocketchef E/AndroidRuntime: at
com.example.rory.pocketchef.activity.LoginActivity.access$200(LoginActivity.java:30) 02-22 15:03:54.296 13823-13823/com.example.rory.pocketchef E/AndroidRuntime: at com.example.rory.pocketchef.activity.LoginActivity$1.onClick(LoginActivity.java:78)
