android - 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>