Tentative d'invoquer la méthode virtuelle " void android.de soutien.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' sur un objet nul de référence

Je suis confronté à cette erreur. J'ai passé beaucoup de temps, mais hélas! Je suis coincé dans cette erreur. Je veux ajouter de la Barre d'Action dans mon application, mais il est en permanence en me montrant cette erreur à getSupportActionBar(), plaire à tout le monde de me guider.

FATAL EXCEPTION: main
Process: com.technerdshub.vusocial, PID: 20633
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.technerdshub.vusocial/com.technerdshub.vusocial.Activities.StudentDashboardActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2693)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)
  at android.app.ActivityThread.access$900(ActivityThread.java:177)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:145)
  at android.app.ActivityThread.main(ActivityThread.java:5942)
  at java.lang.reflect.Method.invoke(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:372)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1389)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1184)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
  at com.technerdshub.vusocial.Activities.StudentDashboardActivity.onCreate(StudentDashboardActivity.java:50)
  

Mon fichier java est:

package com.technerdshub.vusocial.Activities;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.Toolbar;
import android.support.v7.app.AppCompatActivity;
import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.common.api.GoogleApiClient;
import com.technerdshub.vusocial.Fragments.TaskFragment;
import com.technerdshub.vusocial.Fragments.dummy.DummyContent;
import com.technerdshub.vusocial.R;
import java.util.ArrayList;
import java.util.List;
public class StudentDashboardActivity extends AppCompatActivity {
//private Toolbar toolbar;
private TabLayout tabLayout;
private ViewPager viewPager;
/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
private GoogleApiClient client;
@Override
protected void onCreate(Bundle savedInstanceState) {
displayLoginActivity();
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_student_dashboard);
//       Parse.initialize(new Parse.Configuration.Builder(this)
//                       .applicationId("J5CIV2z6xeSCXDqdOfhE0kPSikvRFPyDyOJxqJNx")
//                       .clientKey("bEWm4nWtWiBrMczGfOvA7s4Ulr2bAU3W3TtVSLDf")
//                       .build()
//       );
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setElevation(2);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
//       ParseObject testObject = new ParseObject("Task");
//       testObject.put("marks", 99);
//       testObject.saveInBackground();
//ATTENTION: This was auto-generated to implement the App Indexing API.
//See https://g.co/AppIndexing/AndroidStudio for more information.
client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(new TaskFragment(), "Quiz");
adapter.addFragment(new TaskFragment(), "Assignment");
adapter.addFragment(new TaskFragment(), "GDP");
viewPager.setAdapter(adapter);
}
private void displayLoginActivity() {
Intent i = new Intent(this, Login.class);
startActivity(i);
}
@Override
public void onStart() {
super.onStart();
//ATTENTION: This was auto-generated to implement the App Indexing API.
//See https://g.co/AppIndexing/AndroidStudio for more information.
client.connect();
Action viewAction = Action.newAction(
Action.TYPE_VIEW, //TODO: choose an action type.
"StudentDashboard Page", //TODO: Define a title for the content shown.
//TODO: If you have web page content that matches this app activity's content,
//make sure this auto-generated web page URL is correct.
//Otherwise, set the URL to null.
Uri.parse("http://host/path"),
//TODO: Make sure this auto-generated app URL is correct.
Uri.parse("android-app://com.technerdshub.vusocial.Activities/http/host/path")
);
AppIndex.AppIndexApi.start(client, viewAction);
}
@Override
public void onStop() {
super.onStop();
//ATTENTION: This was auto-generated to implement the App Indexing API.
//See https://g.co/AppIndexing/AndroidStudio for more information.
Action viewAction = Action.newAction(
Action.TYPE_VIEW, //TODO: choose an action type.
"StudentDashboard Page", //TODO: Define a title for the content shown.
//TODO: If you have web page content that matches this app activity's content,
//make sure this auto-generated web page URL is correct.
//Otherwise, set the URL to null.
Uri.parse("http://host/path"),
//TODO: Make sure this auto-generated app URL is correct.
Uri.parse("android-app://com.technerdshub.vusocial.Activities/http/host/path")
);
AppIndex.AppIndexApi.end(client, viewAction);
client.disconnect();
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<TaskFragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public TaskFragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(TaskFragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
}

OriginalL'auteur nabia saroosh | 2016-05-23