training/implementing-navigation/lateral.jd

page.title=Creating Swipe Views with Tabs
page.tags="viewpager","horizontal","paging","swipe view","tabs"

trainingnavtop=true

@jd:body

<div id="tb-wrapper">
<div id="tb">

<h2>This lesson teaches you to</h2>
<ol>
  <li><a href="#horizontal-paging">Implement Swipe Views</a></li>
  <li><a href="#tabs">Add Tabs to the Action Bar</a></li>
  <li><a href="#swipe-tabs">Change Tabs with Swipe Views</a></li>
  <li><a href="#PagerTitleStrip">Use a Title Strip Instead of Tabs</a></li>
</ol>


<h2>You should also read</h2>
<ul>
  <li><a href="{@docRoot}training/design-navigation/descendant-lateral.html">Providing Descendant and Lateral Navigation</a></li>
  <li><a href="{@docRoot}design/building-blocks/tabs.html">Android Design: Tabs</a></li>
  <li><a href="{@docRoot}design/patterns/swipe-views.html">Android Design: Swipe Views</a></li>
</ul>

<h2>Try it out</h2>

<div class="download-box">
<a href="http://developer.android.com/shareables/training/EffectiveNavigation.zip"
  class="button">Download the sample app</a>
<p class="filename">EffectiveNavigation.zip</p>
</div>

</div>
</div>


<p>Swipe views provide lateral navigation between sibling screens such as tabs with
a horizontal finger gesture (a pattern sometimes known as horizontal paging). This lesson teaches
you how to create a tab layout with swipe views for switching between tabs, or how to show
a title strip instead of tabs.</p>

<div class="note design">
<p><strong>Swipe View Design</strong></p>
<p>Before implementing these features, you should understand the concepts and recommendations
as described in <a href="{@docRoot}training/design-navigation/descendant-lateral.html">Designing
Effective Navigation</a> and the <a href="{@docRoot}design/patterns/swipe-views.html">Swipe
Views</a> design guide.</p>
</div>


<h2 id="horizontal-paging">Implement Swipe Views</h2>

<p>You can create swipe views in your app using the {@link android.support.v4.view.ViewPager}
widget, available in the
<a href="{@docRoot}tools/support-library/index.html">Support Library</a>. The
{@link android.support.v4.view.ViewPager} is a layout widget in which each child view is
a separate page (a separate tab) in the layout.</p>

<p>To set up your layout with {@link android.support.v4.view.ViewPager}, add a
{@code &lt;ViewPager>} element to your XML layout. For example, if each page in the swipe view
should consume the entire layout, then your layout looks like this:</p>

<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;android.support.v4.view.ViewPager
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
</pre>

<p>To insert child views that represent each page,
you need to hook this layout to a {@link android.support.v4.view.PagerAdapter}.
There are two kinds of adapter you can use:</p>

<dl>
    <dt>{@link android.support.v4.app.FragmentPagerAdapter}</dt>
        <dd>This is best when navigating between sibling screens representing a fixed, small
        number of pages.</dd>
    <dt>{@link android.support.v4.app.FragmentStatePagerAdapter}</dt>
        <dd>This is best for paging across a collection of objects
for which the number of pages is undetermined. It destroys
fragments as the user navigates to other pages, minimizing memory usage.</dd>
</dl>

<p>For example, here's how you might use {@link android.support.v4.app.FragmentStatePagerAdapter}
to swipe across a collection of {@link android.app.Fragment} objects:</p>

<pre>
public class CollectionDemoActivity extends FragmentActivity {
    // When requested, this adapter returns a DemoObjectFragment,
    // representing an object in the collection.
    DemoCollectionPagerAdapter mDemoCollectionPagerAdapter;
    ViewPager mViewPager;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_collection_demo);

        // ViewPager and its adapters use support library
        // fragments, so use getSupportFragmentManager.
        mDemoCollectionPagerAdapter =
                new DemoCollectionPagerAdapter(
                        getSupportFragmentManager());
        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mDemoCollectionPagerAdapter);
    }
}

// Since this is an object collection, use a FragmentStatePagerAdapter,
// and NOT a FragmentPagerAdapter.
public class DemoCollectionPagerAdapter extends FragmentStatePagerAdapter {
    public DemoCollectionPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    {@literal @}Override
    public Fragment getItem(int i) {
        Fragment fragment = new DemoObjectFragment();
        Bundle args = new Bundle();
        // Our object is just an integer :-P
        args.putInt(DemoObjectFragment.ARG_OBJECT, i + 1);
        fragment.setArguments(args);
        return fragment;
    }

    {@literal @}Override
    public int getCount() {
        return 100;
    }

    {@literal @}Override
    public CharSequence getPageTitle(int position) {
        return "OBJECT " + (position + 1);
    }
}

// Instances of this class are fragments representing a single
// object in our collection.
public static class DemoObjectFragment extends Fragment {
    public static final String ARG_OBJECT = "object";

    {@literal @}Override
    public View onCreateView(LayoutInflater inflater,
            ViewGroup container, Bundle savedInstanceState) {
        // The last two arguments ensure LayoutParams are inflated
        // properly.
        View rootView = inflater.inflate(
                R.layout.fragment_collection_object, container, false);
        Bundle args = getArguments();
        ((TextView) rootView.findViewById(android.R.id.text1)).setText(
                Integer.toString(args.getInt(ARG_OBJECT)));
        return rootView;
    }
}
</pre>

<p>This example shows only the code necessary to create the swipe views. The following
sections show how you can add tabs to help facilitate navigation between pages.</p>


<h2 id="tabs">Add Tabs to the Action Bar</h2>

<p>Action bar
<a href="{@docRoot}design/building-blocks/tabs.html">tabs</a> offer users a familiar interface
for navigating between and identifying sibling screens in your app.</p>

<p>To create tabs using {@link android.app.ActionBar}, you need to enable
{@link android.app.ActionBar#NAVIGATION_MODE_TABS}, then create several instances of
{@link android.app.ActionBar.Tab} and supply an implementation of
the {@link android.app.ActionBar.TabListener} interface for each one.
For example, in your activity's {@link
android.app.Activity#onCreate onCreate()} method, you can use code similar to this:</p>

<pre>
{@literal @}Override
public void onCreate(Bundle savedInstanceState) {
    final ActionBar actionBar = getActionBar();
    ...

    // Specify that tabs should be displayed in the action bar.
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    // Create a tab listener that is called when the user changes tabs.
    ActionBar.TabListener tabListener = new ActionBar.TabListener() {
        public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
            // show the given tab
        }

        public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
            // hide the given tab
        }

        public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
            // probably ignore this event
        }
    };

    // Add 3 tabs, specifying the tab's text and TabListener
    for (int i = 0; i &lt; 3; i++) {
        actionBar.addTab(
                actionBar.newTab()
                        .setText("Tab " + (i + 1))
                        .setTabListener(tabListener));
    }
}
</pre>

<p>How you handle the {@link android.app.ActionBar.TabListener} callbacks to change tabs
depends on how you've constructed your content. But if you're using fragments for each tab with
{@link android.support.v4.view.ViewPager} as shown above, the following
section shows how to switch between pages when the user selects a tab and also update the selected
tab when the user swipes between pages.</p>


<h2 id="swipe-tabs">Change Tabs with Swipe Views</h2>

<p>To switch between pages in a {@link android.support.v4.view.ViewPager} when the user selects
a tab, implement your {@link android.app.ActionBar.TabListener} to select the appropriate page
by calling {@link android.support.v4.view.ViewPager#setCurrentItem setCurrentItem()} on your
{@link android.support.v4.view.ViewPager}:</p>

<pre>
{@literal @}Override
public void onCreate(Bundle savedInstanceState) {
    ...

    // Create a tab listener that is called when the user changes tabs.
    ActionBar.TabListener tabListener = new ActionBar.TabListener() {
        public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
            // When the tab is selected, switch to the
            // corresponding page in the ViewPager.
            mViewPager.setCurrentItem(tab.getPosition());
        }
        ...
    };
}
</pre>

<p>Likewise, you should select the corresponding tab when the user swipes between pages with a
touch gesture. You can set up this behavior by implementing the
{@link android.support.v4.view.ViewPager.OnPageChangeListener} interface to change
the current tab each time the page changes. For example:</p>

<pre>
{@literal @}Override
public void onCreate(Bundle savedInstanceState) {
    ...

    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setOnPageChangeListener(
            new ViewPager.SimpleOnPageChangeListener() {
                {@literal @}Override
                public void onPageSelected(int position) {
                    // When swiping between pages, select the
                    // corresponding tab.
                    getActionBar().setSelectedNavigationItem(position);
                }
            });
    ...
}
</pre>


<h2 id="PagerTitleStrip">Use a Title Strip Instead of Tabs</h2>

<p>If you don't want to include action bar tabs and prefer to provide
<a href="{@docRoot}design/building-blocks/tabs.html#scrollable">scrollable tabs</a> for a shorter
visual profile, you can use {@link android.support.v4.view.PagerTitleStrip} with
your swipe views.</p>

<p>Below is an example layout XML file for an
activity whose entire contents are a {@link android.support.v4.view.ViewPager} and a top-aligned
{@link android.support.v4.view.PagerTitleStrip} inside it. Individual pages (provided by the
adapter) occupy the remaining space inside the {@link android.support.v4.view.ViewPager}.</p>

<pre>
&lt;android.support.v4.view.ViewPager
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"&gt;

    &lt;android.support.v4.view.PagerTitleStrip
        android:id="@+id/pager_title_strip"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top"
        android:background="#33b5e5"
        android:textColor="#fff"
        android:paddingTop="4dp"
        android:paddingBottom="4dp" /&gt;

&lt;/android.support.v4.view.ViewPager&gt;
</pre>