CODEWITHSUNDEEP
androidandroid-actionbaractivity
sasikanth
sasikanth

Reputation: 129

getting Null pointer exception while setting the title to action bar

Error:Caused by: java.lang.NullPointerException: Attempt to invoke   
virtual method 'void android.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference

tried with getSupportActionBar() also not able to resolve the exception please help me out in resolving this

I tried with v7 version of ActionBarActivity, extended the class with AppCompactActivity still not able to resolve.

Executed on both emulator and on real device same issue. After opening the app its its showing unfortunately "app" stopped working.

package pizzandburger.hfad.com.pizzaandburger;

        import android.app.Activity;
        import android.app.Fragment;
        import android.app.FragmentManager;
        import android.app.FragmentTransaction;
        import android.content.Intent;
        import android.content.res.Configuration;
        import android.os.Bundle;
        import android.support.v4.widget.DrawerLayout;
        import android.support.v7.app.ActionBarDrawerToggle;
        import android.view.Menu;
        import android.view.MenuItem;
        import android.view.View;
        import android.widget.AdapterView;
        import android.widget.ArrayAdapter;
        import android.widget.ListView;
        import android.widget.ShareActionProvider;


        public class MainActivity extends Activity {

            private String[] titles;
            private ListView drawerList;
            private DrawerLayout drawerLayout;
            private ActionBarDrawerToggle drawerToggle;
            private ShareActionProvider shareActionProvider;
            private int currentPosition=0;
            private class DrawerItemClickListener implements  ListView.OnItemClickListener{

                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    selectItem(position);
                }
            };

            @Override
            protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.activity_main);
                titles=getResources().getStringArray(R.array.items);
                drawerList=(ListView)findViewById(R.id.drawer);
                drawerLayout=(DrawerLayout)findViewById(R.id.drawer_layout);
                drawerList.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_activated_1,titles));
                drawerList.setOnItemClickListener(new DrawerItemClickListener());
                if(savedInstanceState!=null){
                    currentPosition=savedInstanceState.getInt("position");
                    setActionBarTitle(currentPosition);
                }
                else{
                    selectItem(0);
                }
                drawerToggle=new ActionBarDrawerToggle(this,drawerLayout,R.string.open_drawer,R.string.close_drawer){
                    @Override
                    public void onDrawerClosed(View view){
                        super.onDrawerClosed(view);
                        invalidateOptionsMenu();
                    }
                    @Override
                    public void onDrawerOpened(View drawerView){
                        super.onDrawerOpened(drawerView);
                        invalidateOptionsMenu();
                    }
                };
                drawerLayout.setDrawerListener(drawerToggle);
                getActionBar().setDisplayHomeAsUpEnabled(true);
                getActionBar().setHomeButtonEnabled(true);
                getFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
                    @Override
                    public void onBackStackChanged() {
                        FragmentManager fragmentManager=getFragmentManager();
                        Fragment fragment=fragmentManager.findFragmentByTag("visible_fragment");
                        if(fragment instanceof TopFragment){
                            currentPosition=0;
                        }
                        else if(fragment instanceof PizzaFragment){
                            currentPosition=1;
                        }
                        else if(fragment instanceof BurgerFragment){
                            currentPosition=2;
                        }
                        else if(fragment instanceof OtherFragment){
                            currentPosition=3;
                        }
                        else if(fragment instanceof BeveragesFragment){
                            currentPosition=4;
                        }
                        setActionBarTitle(currentPosition);
                        drawerList.setItemChecked(currentPosition,true);
                    }
                });

            }
            private void selectItem(int position){
                Fragment fragment;
                currentPosition=position;
                switch (position){
                    case 1:
                        fragment=new PizzaFragment();
                        break;
                    case 2:
                        fragment=new BurgerFragment();
                        break;
                    case 3:
                        fragment=new OtherFragment();
                        break;
                    case 4:
                        fragment=new BeveragesFragment();
                        break;
                    default:
                        fragment= new TopFragment();
                        break;
                }
                FragmentTransaction ft=getFragmentManager().beginTransaction();
                ft.replace(R.id.content_frame, fragment, "visible_fragment");
                ft.addToBackStack(null);
                ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
                ft.commit();
                setActionBarTitle(position);
                drawerLayout.closeDrawer(drawerList);
            }

            @Override
            public void onConfigurationChanged(Configuration newConfig) {
                super.onConfigurationChanged(newConfig);
                drawerToggle.onConfigurationChanged(newConfig);
            }

            @Override
            protected  void onPostCreate(Bundle savedInstanceState){
                super.onPostCreate(savedInstanceState);
                drawerToggle.syncState();
            }
            @Override
            public void onSaveInstanceState(Bundle outState){
                super.onSaveInstanceState(outState);
                outState.putInt("position",currentPosition);
            }

            @Override
            public boolean onPrepareOptionsMenu(Menu menu){
                boolean drawerOpen=drawerLayout.isDrawerOpen(drawerList);
                menu.findItem(R.id.action_share).setVisible(!drawerOpen);
                return super.onPrepareOptionsMenu(menu);
            }


            private void setActionBarTitle(int position){
                String title;
                if(position==0){
                    title=getResources().getString(R.string.app_name);
                }
                else{
                    title=titles[position];
                }

     /*******************************/
    /**** here its giving error *****/ 
   /*******************************/
                getActionBar().setTitle(title);
            }
            @Override
            public boolean onCreateOptionsMenu(Menu menu){
                getMenuInflater().inflate(R.menu.menu_main, menu);
                MenuItem menuItem=menu.findItem(R.id.action_share);
                shareActionProvider=(ShareActionProvider)menuItem.getActionProvider();
                setIntent("this is some simple text for sharing through shareActionProvider");
                return super.onCreateOptionsMenu(menu);
            }
            @Override
            public boolean onOptionsItemSelected(MenuItem menuitem){
                if(drawerToggle.onOptionsItemSelected(menuitem)){
                    return true;
                }
                switch (menuitem.getItemId()){
                    case R.id.action_settings:
                        return true;
                    default:
                        return super.onOptionsItemSelected(menuitem);
                }
            }
            private void setIntent(String text){
                Intent intent=new Intent(Intent.ACTION_SEND);
                intent.setType("text/plain");
                intent.putExtra(Intent.EXTRA_TEXT,text);
                shareActionProvider.setShareIntent(intent);
            }
        }

Here is my styles.xml

<style name="AppTheme.NoActionBar">
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
    <item name="android:windowDrawsSystemBarBackgrounds">true</item>
    <item name="android:statusBarColor">@android:color/transparent</item>
</style>

and here is my activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/drawer_layout"
    >
    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/content_frame"></FrameLayout>
    <ListView
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:id="@+id/drawer"
        android:layout_gravity="start"
        android:choiceMode="singleChoice"
        android:divider="@android:color/transparent"
        android:dividerHeight="0dp"
        android:background="#ffffff"></ListView>
</android.support.v4.widget.DrawerLayout>
  1. Tried with setting the title manually it didn't work
  2. checked with debugger its unable to get ActionBarObject

Upvotes: 2

Views: 2035

Answers (3)

Thomas LeBlond
Thomas LeBlond

Reputation: 81

If you are using an INTENT with AppCompatActivity, you need to access to the same relevant thread: 

YourClass mContext;
mContext.runOnUiThread(new Runnable() {
    @Override
    public void run() {
        mContext.getSupportActionBar().hide();
    }
});

YourClass is the one extending AppCompActivity:

public class YourClass extends AppCompatActivity {
}

Upvotes: 0

sasikanth
sasikanth

Reputation: 129

Its the problem in the style sheet That says

"<style name="AppTheme.NoActionBar">"

Define some theme then you get rid of null pointer exception

Upvotes: 1

Franklin Hirata
Franklin Hirata

Reputation: 288

Some premisses:

  • Check if you had declared import android.support.v7.app.AppCompatActivityand your activity is extended it.
  • Check if you declared WINDOWS_FEATURE: requestWindowFeature(Window.FEATURE_ACTION_BAR); or in your style: <item name="android:windowActionBar">true</item>

regards,

Upvotes: 1

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