title: E/AndroidRuntime﹕ FATAL EXCEPTION: main
body: <p>while I test my app, I get the follow error in the Android-Studio-Consol:</p>
  
  <pre><code> 10-09 20:44:56.685 21573-21573/com.example.android.buyhatke E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                Process: com.example.android.buyhatke, PID: 21573
                                                                                java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.buyhatke/com.example.android.buyhatke.HomeActivity}: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead.
                                                                                    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.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead.
                                                                                    at android.support.v7.app.AppCompatDelegateImplV7.setSupportActionBar(AppCompatDelegateImplV7.java:198)
                                                                                    at android.support.v7.app.AppCompatActivity.setSupportActionBar(AppCompatActivity.java:130)
                                                                                    at com.example.android.buyhatke.HomeActivity.onCreate(HomeActivity.java:36)
                                                                                    at android.app.Activity.performCreate(Activity.java:6237)
                                                                                    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) 
  10-09 20:49:57.180 26089-26089/com.example.android.buyhatke W/System: ClassLoader referenced unknown path: /data/app/com.example.android.buyhatke-3/lib/x86
  10-09 20:49:58.795 26089-26089/com.example.android.buyhatke W/System: ClassLoader referenced unknown path: /data/app/com.example.android.buyhatke-3/lib/x86
  10-09 20:49:58.905 26089-26089/com.example.android.buyhatke W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
  10-09 20:49:59.023 26089-26089/com.example.android.buyhatke D/AndroidRuntime: Shutting down VM
  10-09 20:49:59.023 26089-26089/com.example.android.buyhatke E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                Process: com.example.android.buyhatke, PID: 26089
                                                                                java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.buyhatke/com.example.android.buyhatke.HomeActivity}: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead.
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                                                                                    at android.app.ActivityThread.-wrap11(ActivityThread.java)
                                                                                    at android.app.ActivityThread$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$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                                                                                 Caused by: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead.
                                                                                    at android.support.v7.app.AppCompatDelegateImplV7.setSupportActionBar(AppCompatDelegateImplV7.java:198)
                                                                                    at android.support.v7.app.AppCompatActivity.setSupportActionBar(AppCompatActivity.java:130)
                                                                                    at com.example.android.buyhatke.HomeActivity.onCreate(HomeActivity.java:36)
                                                                                    at android.app.Activity.performCreate(Activity.java:6237)
                                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                                                                                    at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                                                                                    at android.app.ActivityThread$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) 
  </code></pre>
  
  <p>My codes are</p>
  
  <pre><code>  MainActivity.java
  
  
  
  package com.example.android.buyhatke;
  
  import android.content.Intent;
  import android.os.Bundle;
  import android.support.v7.app.AppCompatActivity;
  import android.util.Log;
  import android.view.Menu;
  import android.view.MenuItem;
  
  import com.facebook.CallbackManager;
  import com.facebook.FacebookCallback;
  import com.facebook.FacebookException;
  import com.facebook.FacebookSdk;
  import com.facebook.GraphRequest;
  import com.facebook.GraphResponse;
  import com.facebook.appevents.AppEventsLogger;
  import com.facebook.login.LoginResult;
  import com.facebook.login.widget.LoginButton;
  
  import org.json.JSONObject;
  
  public class MainActivity extends AppCompatActivity {
  
      CallbackManager callbackManager;
      @Override
      protected void onCreate(Bundle savedInstanceState) {
              super.onCreate(savedInstanceState);
              setContentView(R.layout.activity_main);
          //
              facebookSDKInitialize();
  
              LoginButton loginButton = (LoginButton) findViewById(R.id.login_button);
              loginButton.setReadPermissions("email");
              getLoginDetails(loginButton);
      }
  
      /*
       Initialize the facebook sdk.
       And then callback manager will handle the login responses.&lt;br /&gt;
     */
      protected void facebookSDKInitialize() {
                 FacebookSdk.sdkInitialize(getApplicationContext());
                 callbackManager = CallbackManager.Factory.create();
      }
  
  
      /*
    Register a callback function with LoginButton to respond to the login result.
    On successful login,login result has new access token and  recently granted permissions.
   */
      protected void getLoginDetails(LoginButton login_button){
                  // Callback registration&lt;br /&gt;
          login_button.registerCallback(callbackManager, new FacebookCallback &lt;LoginResult&gt; (){
  
              @Override
              public void onSuccess(LoginResult login_result) {
                  getUserInfo(login_result);
                              }
  
              @Override
              public void onCancel() {
                // code for cancellation
              }
  
              @Override
              public void onError(FacebookException error) {
                // code for error handling.
              }
          });
      }
  
      /*To get the facebook user's own profile information via  creating a new request.
        When the request is completed, a callback is called to handle the success condition. */
  
      protected void getUserInfo(LoginResult login_result){
                 GraphRequest data_request = GraphRequest.newMeRequest(
                  login_result.getAccessToken(),
                  new GraphRequest.GraphJSONObjectCallback() {
                      @Override
                      public void onCompleted( JSONObject json_object, GraphResponse response) {
                          Intent intent = new Intent(MainActivity.this,HomeActivity.class);
                          intent.putExtra("jsondata",json_object.toString());
                                  startActivity(intent);
                      }
                  });
                  Bundle permission_param = new Bundle();
                  permission_param.putString("fields", "id,name,email,picture.width(120).height(120)");
                  data_request.setParameters(permission_param);
                  data_request.executeAsync();
              }
  
  
          @Override
          protected void onActivityResult(int requestCode, int resultCode, Intent data) {
                  super.onActivityResult(requestCode, resultCode, data);
                  callbackManager.onActivityResult(requestCode, resultCode, data);
                  Log.e("data",data.toString());
          }
  
      @Override
      public boolean onCreateOptionsMenu(Menu menu) {
          // Inflate the menu; this adds items to the action bar if it is present.
          // getMenuInflater().inflate(R.menu.menu_main, menu);
          return true;
      }
  
      @Override
      public boolean onOptionsItemSelected(MenuItem item) {
          // Handle action bar item clicks here. The action bar will
          // automatically handle clicks on the Home/Up button, so long
          // as you specify a parent activity in AndroidManifest.xml.
          return super.onOptionsItemSelected(item);
      }
  
      @Override
      protected void onResume() {
          super.onResume();
          // Logs 'install' and 'app activate' App Events.
          AppEventsLogger.activateApp(this);
      }
  
      @Override
      protected void onPause() {
          super.onPause();
          // Logs 'app deactivate' App Event.
          AppEventsLogger.deactivateApp(this);
      }
  }
  </code></pre>
  
  <p>HomeActivity.java</p>
  
  <pre><code>  package com.example.android.buyhatke;
  
      import android.content.Context;
      import android.content.Intent;
      import android.os.Bundle;
      import android.support.design.widget.FloatingActionButton;
      import android.support.design.widget.NavigationView;
      import android.support.design.widget.Snackbar;
      import android.support.v4.view.GravityCompat;
      import android.support.v4.widget.DrawerLayout;
      import android.support.v7.app.ActionBarDrawerToggle;
      import android.support.v7.app.AppCompatActivity;
      import android.support.v7.widget.Toolbar;
      import android.view.LayoutInflater;
      import android.view.Menu;
      import android.view.MenuItem;
      import android.view.View;
      import android.widget.ImageView;
      import android.widget.TextView;
      import android.widget.Toast;
  
      import com.squareup.picasso.Picasso;
  
      import org.json.JSONObject;
  
      public class HomeActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
             JSONObject response, profile_pic_data, profile_pic_url;
              TextView user_name, user_email;
              ImageView user_picture;
              NavigationView navigation_view;
          @Override
              protected void onCreate(Bundle savedInstanceState) {
              super.onCreate(savedInstanceState);
              setContentView(R.layout.activity_home);
              Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
              setSupportActionBar(toolbar);
              getSupportActionBar().setTitle("Home Page");            // may produce null pointer exception
              Intent intent = getIntent();
              String jsondata = intent.getStringExtra("jsondata");
              setNavigationHeader();    // call setNavigationHeader Method.
              setUserProfile(jsondata);  // call setUserProfile Method
  
              FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
              fab.setOnClickListener(new View.OnClickListener() {
                  @Override
              public void onClick(View view) {
              Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
              .setAction("Action", null).show();
              }
              });
              DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
  
              ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this,drawer,toolbar,R.string.openDrawer, R.string.closeDrawer);
                   try {
                       drawer.setDrawerListener(toggle);
                   }catch(NullPointerException e)
                       {
                           Context context = getApplicationContext();
                           CharSequence text = "Error";
                           int duration = Toast.LENGTH_SHORT;
                           Toast toast = Toast.makeText(context, text, duration);
                           toast.show();
                       }
  
                       toggle.syncState();
                      navigation_view.setNavigationItemSelectedListener(this);
          }
          @Override
              public void onBackPressed() {
              DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
              if (drawer.isDrawerOpen(GravityCompat.START)) {
              drawer.closeDrawer(GravityCompat.START);
              } else {
              super.onBackPressed();
              }
              }
            /*
              Set Navigation header by using Layout Inflater.&lt;br /&gt;
             */
             public void setNavigationHeader(){
               navigation_view = (NavigationView) findViewById(R.id.nav_view);
               View header = LayoutInflater.from(this).inflate(R.layout.nav_header_home, null);
               navigation_view.addHeaderView(header);
               user_name = (TextView) header.findViewById(R.id.username);
               user_picture = (ImageView) header.findViewById(R.id.profile_pic);
               user_email = (TextView) header.findViewById(R.id.email);
              }
               /*
                Set User Profile Information in Navigation Bar.&lt;br /&gt;
               */
               public  void  setUserProfile(String jsondata){
              try {
              response = new JSONObject(jsondata);
              user_email.setText(response.get("email").toString());
              user_name.setText(response.get("name").toString());
              profile_pic_data = new JSONObject(response.get("picture").toString());
              profile_pic_url = new JSONObject(profile_pic_data.getString("data"));
                      Picasso.with(this).load(profile_pic_url.getString("url"))
              .into(user_picture);
              } catch (Exception e){
              e.printStackTrace();
              }
              }
          @Override
              public boolean onCreateOptionsMenu(Menu menu) {
                      // Inflate the menu; this adds items to the action bar if it is present.&lt;br /&gt;
                      //   getMenuInflater().inflate(R.menu.home, menu);&lt;br /&gt;
              return true;
              }
          @Override
              public boolean onOptionsItemSelected(MenuItem item) {
                   // Handle action bar item clicks here. The action bar will
                   // automatically handle clicks on the Home/Up button, so long
                   // as you specify a parent activity in AndroidManifest.xml.
              int id = item.getItemId();
                   //noinspection SimplifiableIfStatement
              if (id == R.id.action_settings) {/** check if error*/
              return true;
              }
              return super.onOptionsItemSelected(item);
              }
          @SuppressWarnings("StatementWithEmptyBody")
  
          @Override
            public boolean onNavigationItemSelected(MenuItem item){
              // Handle navigation view item clicks here.
              int id = item.getItemId();
              if (id ==R.id.inbox) {
              // Handle the camera action
              } else if (id ==R.id.starred) {
              }
              else if (id ==R.id.sent_mail) {
  
              }
              else if (id ==R.id.drafts) {
  
              }
              else if (id ==R.id.allmail ) {
  
              }
             else if (id ==R.id.trash ) {
  
              }
              else if (id ==R.id.spam ) {
  
              }
              DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
              drawer.closeDrawer(GravityCompat.START);
              return true;
            }
  
      }
  </code></pre>
  
  <p>can anyone help?</p>