Navigation drawer and view pager in same activity

Question

I am trying to implement both navigation drawer and view pager in same activity. Navigation drawer works fine but the view pager is not working, also i am getting null pointer on right swipe when navigation drawer is opened (Null pointer at android. support. v4. widget. DrawerLayout. isContentView(DrawerLayout.java:840). I am attaching the main xml layout and code below.

<android.support.v4.view.ViewPager     android:id="@+id/viewpager"     android:layout_width="fill_parent"     android:layout_height="fill_parent" > </android.support.v4.view.ViewPager>  <android.support.v4.widget.DrawerLayout     xmlns:android="http://schemas.android.com/apk/res/android"     android:id="@+id/drawer_layout"     android:layout_width="match_parent"     android:layout_height="match_parent" >          <ListView         android:id="@+id/left_drawer"         android:layout_width="240dp"         android:layout_height="match_parent"         android:layout_gravity="start"         android:background="#111"         android:choiceMode="singleChoice"         android:divider="@android:color/transparent"         android:dividerHeight="0dp" /> </android.support.v4.widget.DrawerLayout> 

Activity class is given below

public class MainActivity extends Activity { private DrawerLayout mDrawerLayout; private ListView mDrawerList; private ActionBarDrawerToggle mDrawerToggle;  private CharSequence mDrawerTitle; private CharSequence mTitle; private String[] mPlanetTitles; private MainActivity mContext;  @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main);     mContext = this;     ViewPager vp = (ViewPager) findViewById(R.id.viewpager);     CustomPagerAdapter adapter = new CustomPagerAdapter(mContext);     vp.setAdapter(adapter);     vp.setPageTransformer(false, new ViewPager.PageTransformer() {          @Override         public void transformPage(View page, float position) {             final float normalizedposition = Math.abs(Math.abs(position) - 1);             page.setScaleX(normalizedposition / 2 + 0.5f);             page.setScaleY(normalizedposition / 2 + 0.5f);         }     });      mTitle = mDrawerTitle = getTitle();     mPlanetTitles = getResources().getStringArray(R.array.planets_array);     mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);     mDrawerList = (ListView) findViewById(R.id.left_drawer);      // set a custom shadow that overlays the main content when the drawer     // opens     mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);     // set up the drawer's list view with items and click listener     mDrawerList.setAdapter(new ArrayAdapter<String>(this,             R.layout.drawer_list_item, mPlanetTitles));     mDrawerList.setOnItemClickListener(new DrawerItemClickListener());      // enable ActionBar app icon to behave as action to toggle nav drawer     getActionBar().setDisplayHomeAsUpEnabled(true);     getActionBar().setHomeButtonEnabled(true);      // ActionBarDrawerToggle ties together the the proper interactions     // between the sliding drawer and the action bar app icon     mDrawerToggle = new ActionBarDrawerToggle(             this, /* host Activity */             mDrawerLayout, /* DrawerLayout object */             R.drawable.ic_drawer, /* nav drawer image to replace 'Up' caret */             R.string.drawer_open, /*                                    * "open drawer" description for                                    * accessibility                                    */             R.string.drawer_close /*                                    * "close drawer" description for                                    * accessibility                                    */             ) {                 @Override                 public void onDrawerClosed(View view) {                     getActionBar().setTitle(mTitle);                     invalidateOptionsMenu(); // creates call to                                              // onPrepareOptionsMenu()                 }                  @Override                 public void onDrawerOpened(View drawerView) {                     getActionBar().setTitle(mDrawerTitle);                     invalidateOptionsMenu(); // creates call to                                              // onPrepareOptionsMenu()                 }              };     mDrawerLayout.setDrawerListener(mDrawerToggle);      if (savedInstanceState == null) {         selectItem(0);     } }  @Override public boolean onPrepareOptionsMenu(Menu menu) {     // If the nav drawer is open, hide action items related to the content     // view     boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);     return super.onPrepareOptionsMenu(menu); }  @Override public boolean onOptionsItemSelected(MenuItem item) {     // The action bar home/up action should open or close the drawer.     // ActionBarDrawerToggle will take care of this.     if (mDrawerToggle.onOptionsItemSelected(item)) {         return true;     }     // Handle action buttons     return true; }  /* The click listner for ListView in the navigation drawer */ private class DrawerItemClickListener implements ListView.OnItemClickListener {     @Override     public void onItemClick(AdapterView<?> parent, View view, int position, long id) {         selectItem(position);     } }  private void selectItem(int position) {      // update selected item and title, then close the drawer     mDrawerList.setItemChecked(position, true);     setTitle(mPlanetTitles[position]);     mDrawerLayout.closeDrawer(mDrawerList); }  @Override public boolean onCreateOptionsMenu(Menu menu) {     // Inflate the menu; this adds items to the action bar if it is present.     getMenuInflater().inflate(R.menu.main, menu);     return true; }  @Override protected void onPostCreate(Bundle savedInstanceState) {     super.onPostCreate(savedInstanceState);     // Sync the toggle state after onRestoreInstanceState has occurred.     mDrawerToggle.syncState(); }  public class CustomPagerAdapter extends PagerAdapter {      private Context context;      int index = 2;      // public CustomPagerAdapter(Context context, Vector<View> pages) {     // this.context = context;     // this.pages = pages;     // }      public CustomPagerAdapter(Context context) {         this.context = context;         this.index = 2;     }      @Override     public Object instantiateItem(ViewGroup container, int position) {         LayoutInflater inflater = (LayoutInflater.from(container.getContext()));         // View page = pages.get(position);         View view = null;         if (position == 0) {             view = inflater.inflate(R.layout.page_one_views, null);             ((ViewPager) container).addView(view);          }         else {             // page.setBackgroundColor(colors.get(position));             // container.addView(page);             view = inflater.inflate(R.layout.page_two, null);             ((ViewPager) container).addView(view);         }         return view;     }      @Override     public int getCount() {         return index;     }      @Override     public boolean isViewFromObject(View view, Object object) {         return view.equals(object);     }      @Override     public void destroyItem(ViewGroup container, int position, Object object) {         container.removeView((View) object);     }  } 

}

Please help me. Thanks in advance

Answer 1

The DrawerLayout should be the root element. Put the ViewPager inside it.

<android.support.v4.widget.DrawerLayout      xmlns:android="http://schemas.android.com/apk/res/android"     android:id="@+id/drawer_layout"     android:layout_width="match_parent"     android:layout_height="match_parent">      <android.support.v4.view.ViewPager         android:id="@+id/viewpager"         android:layout_width="fill_parent"         android:layout_height="fill_parent" />      <ListView          android:id="@+id/left_drawer"         android:layout_width="240dp"         android:layout_height="match_parent"         android:layout_gravity="start"         android:background="#111"         android:choiceMode="singleChoice"         android:divider="@android:color/transparent"         android:dividerHeight="0dp" /> </android.support.v4.widget.DrawerLayout>