I am Working on Android Project , Error i am facing displayed below , i am trying to call prefrenceManager from login activity through MyApplication instance, but i am geting null pointer exception i dont know why , i might not grabbing the getPrefM() but i check all , everything seems to be fine , where i am making a mistake , kindly help me out .
01-01 15:32:35.571 32658-32658/com.adnan.zwd.hidoctor E/UncaughtException: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.adnan.zwd.hidoctor/com.adnan.zwd.hidoctor.activity.Login_Act}: java.lang.NullPointerException: Attempt to invoke virtual method 'com.adnan.zwd.hidoctor.helper.MyPrefM com.adnan.zwd.hidoctor.app.MyApplication.getPrefM()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.adnan.zwd.hidoctor.helper.MyPrefM com.adnan.zwd.hidoctor.app.MyApplication.getPrefM()' on a null object reference
at com.adnan.zwd.hidoctor.activity.Login_Act.onCreate(Login_Act.java:54)
at android.app.Activity.performCreate(Activity.java:6251)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Login_Act.java:
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.TextInputLayout;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.text.Editable;
import android.text.TextUtils;
import android.text.TextWatcher;
import android.util.Log;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import com.android.volley.NetworkResponse;
import com.android.volley.Request;
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.adnan.zwd.hidoctor.R;
import com.adnan.zwd.hidoctor.app.EndPoints;
import com.adnan.zwd.hidoctor.app.MyApplication;
import com.adnan.zwd.hidoctor.model.User;
public class Login_Act extends AppCompatActivity {
private String TAG = Login_Act.class.getSimpleName();
private EditText inputName, inputEmail;
private TextInputLayout inputLayoutName, inputLayoutEmail;
private Button btnEnter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/**
* Check for login session. It user is already logged in
* redirect him to main activity
* */
if (MyApplication.getInstance().getPrefM().getUser() != null) {
startActivity(new Intent(this, Main_Act.class));
finish();
}
setContentView(R.layout.login_activity);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
inputLayoutName = (TextInputLayout) findViewById(R.id.input_layout_name);
inputLayoutEmail = (TextInputLayout) findViewById(R.id.input_layout_email);
inputName = (EditText) findViewById(R.id.input_name);
inputEmail = (EditText) findViewById(R.id.input_email);
btnEnter = (Button) findViewById(R.id.btn_enter);
inputName.addTextChangedListener(new MyTextWatcher(inputName));
inputEmail.addTextChangedListener(new MyTextWatcher(inputEmail));
btnEnter.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
login();
}
});
}
/**
* logging in user. Will make http post request with name, email
* as parameters
*/
private void login() {
if (!validateName()) {
return;
}
if (!validateEmail()) {
return;
}
final String name = inputName.getText().toString();
final String email = inputEmail.getText().toString();
StringRequest strReq = new StringRequest(Request.Method.POST,
EndPoints.LOGIN, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Log.e(TAG, "response: " + response);
try {
JSONObject obj = new JSONObject(response);
// check for error flag
if (obj.getBoolean("error") == false) {
// user successfully logged in
JSONObject userObj = obj.getJSONObject("user");
User user = new User(userObj.getString("user_id"),
userObj.getString("name"),
userObj.getString("email"));
// storing user in shared preferences
MyApplication.getInstance().getPrefM().storeUser(user);
// start main activity
startActivity(new Intent(getApplicationContext(), Main_Act.class));
finish();
} else {
// login error - simply toast the message
Toast.makeText(getApplicationContext(), "" + obj.getJSONObject("error").getString("message"), Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
Log.e(TAG, "json parsing error: " + e.getMessage());
Toast.makeText(getApplicationContext(), "Json parse error: " + e.getMessage(), Toast.LENGTH_SHORT).show();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
NetworkResponse networkResponse = error.networkResponse;
Log.e(TAG, "Volley error: " + error.getMessage() + ", code: " + networkResponse);
Toast.makeText(getApplicationContext(), "Volley error: " + error.getMessage(), Toast.LENGTH_SHORT).show();
}
}) {
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<>();
params.put("name", name);
params.put("email", email);
Log.e(TAG, "params: " + params.toString());
return params;
}
};
//Adding request to request queue
MyApplication.getInstance().addToRequestQueue(strReq);
}
private void requestFocus(View view) {
if (view.requestFocus()) {
getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);
}
}
// Validating name
private boolean validateName() {
if (inputName.getText().toString().trim().isEmpty()) {
inputLayoutName.setError(getString(R.string.err_msg_name));
requestFocus(inputName);
return false;
} else {
inputLayoutName.setErrorEnabled(false);
}
return true;
}
// Validating email
private boolean validateEmail() {
String email = inputEmail.getText().toString().trim();
if (email.isEmpty() || !isValidEmail(email)) {
inputLayoutEmail.setError(getString(R.string.err_msg_email));
requestFocus(inputEmail);
return false;
} else {
inputLayoutEmail.setErrorEnabled(false);
}
return true;
}
private static boolean isValidEmail(String email) {
return !TextUtils.isEmpty(email) && android.util.Patterns.EMAIL_ADDRESS.matcher(email).matches();
}
private class MyTextWatcher implements TextWatcher {
private View view;
private MyTextWatcher(View view) {
this.view = view;
}
public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
}
public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
}
public void afterTextChanged(Editable editable) {
switch (view.getId()) {
case R.id.input_name:
validateName();
break;
case R.id.input_email:
validateEmail();
break;
}
}
}
}
MyApplication.java:
public class MyApplication extends Application {
public static final String TAG = MyApplication.class
.getSimpleName();
private RequestQueue mRequestQueue;
private static MyApplication mInstance;
private MyPrefM pref;
@Override
public void onCreate() {
super.onCreate();
mInstance = MyApplication.this;
}
public static synchronized MyApplication getInstance() {
return mInstance;
}
public RequestQueue getRequestQueue() {
if (mRequestQueue == null) {
mRequestQueue = Volley.newRequestQueue(getApplicationContext());
}
return mRequestQueue;
}
public MyPrefM getPrefM() {
if (pref == null) {
pref = new MyPrefM(MyApplication.this);
}
return pref;
}
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);
}
}
public void logout() {
pref.clear();
Intent intent = new Intent(this, Login_Act.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
}
}
MyPrefM.java:
public class MyPrefM {
private String TAG = MyPrefM.class.getSimpleName();
// Shared Preferences
SharedPreferences pref;
// Editor for Shared preferences
SharedPreferences.Editor editor;
// Context
Context _context;
// Shared pref mode
int PRIVATE_MODE = 0;
// Sharedpref file name
private static final String PREF_NAME = "androidhive_gcm";
// All Shared Preferences Keys
private static final String KEY_USER_ID = "user_id";
private static final String KEY_USER_NAME = "user_name";
private static final String KEY_USER_EMAIL = "user_email";
private static final String KEY_NOTIFICATIONS = "notifications";
// Constructor
public MyPrefM(Context context) {
this._context = context;
pref = _context.getSharedPreferences(PREF_NAME, PRIVATE_MODE);
editor = pref.edit();
}
public void storeUser(User user) {
editor.putString(KEY_USER_ID, user.getId());
editor.putString(KEY_USER_NAME, user.getName());
editor.putString(KEY_USER_EMAIL, user.getEmail());
editor.commit();
Log.e(TAG, "User is stored in shared preferences. " + user.getName() + ", " + user.getEmail());
}
public User getUser() {
if (pref.getString(KEY_USER_ID, null) != null) {
String id, name, email;
id = pref.getString(KEY_USER_ID, null);
name = pref.getString(KEY_USER_NAME, null);
email = pref.getString(KEY_USER_EMAIL, null);
User user = new User(id, name, email);
return user;
}
return null;
}
public void addNotification(String notification) {
// get old notifications
String oldNotifications = getNotifications();
if (oldNotifications != null) {
oldNotifications += "|" + notification;
} else {
oldNotifications = notification;
}
editor.putString(KEY_NOTIFICATIONS, oldNotifications);
editor.commit();
}
public String getNotifications() {
return pref.getString(KEY_NOTIFICATIONS, null);
}
public void clear() {
editor.clear();
editor.commit();
}
}
