Retroactively add EffectiveNavigation and TabCompat sample code.

This sample code was launched with the Implementing Effective Navigation and
Creating Backward-Compatible UIs training classes, but the source was never
added to AOSP. This retroactively adds the source, unmodified.

Change-Id: If6face5a0548107f7fd273e466b1ced2790f4f3a

samples/training/TabCompat/src/com/example/android/tabcompat/MainActivity.java

@@ -0,0 +1,129 @@
+/*
+ * Copyright 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.android.tabcompat;
+
+import com.example.android.tabcompat.lib.CompatTab;
+import com.example.android.tabcompat.lib.CompatTabListener;
+import com.example.android.tabcompat.lib.TabCompatActivity;
+import com.example.android.tabcompat.lib.TabHelper;
+
+import android.os.Bundle;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentTransaction;
+import android.view.Gravity;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.TextView;
+
+public class MainActivity extends TabCompatActivity {
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.main);
+
+        TabHelper tabHelper = getTabHelper();
+
+        CompatTab photosTab = tabHelper.newTab("photos")
+                .setText(R.string.tab_photos)
+                .setIcon(R.drawable.ic_tab_photos)
+                .setTabListener(new InstantiatingTabListener(this, PhotosFragment.class));
+        tabHelper.addTab(photosTab);
+
+        CompatTab videosTab = tabHelper.newTab("videos")
+                .setText(R.string.tab_videos)
+                .setIcon(R.drawable.ic_tab_videos)
+                .setTabListener(new InstantiatingTabListener(this, VideosFragment.class));
+        tabHelper.addTab(videosTab);
+    }
+
+    /**
+     * Implementation of {@link CompatTabListener} to handle tab change events. This implementation
+     * instantiates the specified fragment class with no arguments when its tab is selected.
+     */
+    public static class InstantiatingTabListener implements CompatTabListener {
+
+        private final TabCompatActivity mActivity;
+        private final Class mClass;
+
+        /**
+         * Constructor used each time a new tab is created.
+         *
+         * @param activity The host Activity, used to instantiate the fragment
+         * @param cls      The class representing the fragment to instantiate
+         */
+        public InstantiatingTabListener(TabCompatActivity activity, Class<? extends Fragment> cls) {
+            mActivity = activity;
+            mClass = cls;
+        }
+
+        /* The following are each of the ActionBar.TabListener callbacks */
+        @Override
+        public void onTabSelected(CompatTab tab, FragmentTransaction ft) {
+            // Check if the fragment is already initialized
+            Fragment fragment = tab.getFragment();
+            if (fragment == null) {
+                // If not, instantiate and add it to the activity
+                fragment = Fragment.instantiate(mActivity, mClass.getName());
+                tab.setFragment(fragment);
+                ft.add(android.R.id.tabcontent, fragment, tab.getTag());
+            } else {
+                // If it exists, simply attach it in order to show it
+                ft.attach(fragment);
+            }
+        }
+
+        @Override
+        public void onTabUnselected(CompatTab tab, FragmentTransaction ft) {
+            Fragment fragment = tab.getFragment();
+            if (fragment != null) {
+                // Detach the fragment, because another one is being attached
+                ft.detach(fragment);
+            }
+        }
+
+        @Override
+        public void onTabReselected(CompatTab tab, FragmentTransaction ft) {
+            // User selected the already selected tab. Do nothing.
+        }
+    }
+
+    public static class PhotosFragment extends Fragment {
+
+        @Override
+        public View onCreateView(LayoutInflater inflater, ViewGroup container,
+                Bundle savedInstanceState) {
+            TextView textView = new TextView(getActivity());
+            textView.setGravity(Gravity.CENTER);
+            textView.setText(R.string.tab_photos);
+            return textView;
+        }
+    }
+
+    public static class VideosFragment extends Fragment {
+
+        @Override
+        public View onCreateView(LayoutInflater inflater, ViewGroup container,
+                Bundle savedInstanceState) {
+            TextView textView = new TextView(getActivity());
+            textView.setGravity(Gravity.CENTER);
+            textView.setText(R.string.tab_videos);
+            return textView;
+        }
+    }
+}

samples/training/TabCompat/src/com/example/android/tabcompat/lib/CompatTab.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.android.tabcompat.lib;
+
+import android.graphics.drawable.Drawable;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentActivity;
+
+/**
+ * Represents a single tab.
+ * The {@link TabHelper} initializes one of the subclasses of this based
+ * on the current platform version, upon call to {@link TabHelper#newTab(String)}()
+ */
+public abstract class CompatTab {
+    final FragmentActivity mActivity;
+    final String mTag;
+
+    protected CompatTab(FragmentActivity activity, String tag) {
+        mActivity = activity;
+        mTag = tag;
+    }
+
+    public abstract CompatTab setText(int resId);
+    public abstract CompatTab setIcon(int resId);
+    public abstract CompatTab setTabListener(CompatTabListener callback);
+    public abstract CompatTab setFragment(Fragment fragment);
+
+    public abstract CharSequence getText();
+    public abstract Drawable getIcon();
+    public abstract CompatTabListener getCallback();
+    public abstract Fragment getFragment();
+
+    public abstract Object getTab();
+
+    public String getTag() {
+        return mTag;
+    }
+}

samples/training/TabCompat/src/com/example/android/tabcompat/lib/CompatTabEclair.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.android.tabcompat.lib;
+
+import android.graphics.drawable.Drawable;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentActivity;
+
+/**
+ * A base implementation of the {@link CompatTab} interface.
+ */
+public class CompatTabEclair extends CompatTab {
+    private CompatTabListener mCallback;
+    private CharSequence mText;
+    private Drawable mIcon;
+    private Fragment mFragment;
+
+    protected CompatTabEclair(FragmentActivity activity, String tag) {
+        super(activity, tag);
+    }
+
+    @Override
+    public CompatTab setText(int resId) {
+        mText = mActivity.getResources().getText(resId);
+        return this;
+    }
+
+    @Override
+    public CompatTab setIcon(int resId) {
+        mIcon = mActivity.getResources().getDrawable(resId);
+        return this;
+    }
+
+    @Override
+    public CompatTab setTabListener(CompatTabListener callback) {
+        mCallback = callback;
+        return this;
+    }
+
+    @Override
+    public CompatTab setFragment(Fragment fragment) {
+        mFragment = fragment;
+        return this;
+    }
+
+    @Override
+    public Fragment getFragment() {
+        return mFragment;
+    }
+
+    @Override
+    public CharSequence getText() {
+        return mText;
+    }
+
+    @Override
+    public Drawable getIcon() {
+        return mIcon;
+    }
+
+    @Override
+    public Object getTab() {
+        return null;
+    }
+
+    @Override
+    public CompatTabListener getCallback() {
+        return mCallback;
+    }
+}

samples/training/TabCompat/src/com/example/android/tabcompat/lib/CompatTabHoneycomb.java

@@ -0,0 +1,116 @@
+/*
+ * Copyright 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.android.tabcompat.lib;
+
+import android.app.ActionBar;
+import android.app.ActionBar.Tab;
+import android.graphics.drawable.Drawable;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentActivity;
+import android.support.v4.app.FragmentTransaction;
+
+/**
+ * An implementation of the {@link CompatTab} interface that relies on API 11 APIs.
+ */
+public class CompatTabHoneycomb extends CompatTab implements ActionBar.TabListener {
+
+    /**
+     * The native tab object that this {@link CompatTab} acts as a proxy for.
+     */
+    ActionBar.Tab mTab;
+    CompatTabListener mCallback;
+    Fragment mFragment;
+
+    protected CompatTabHoneycomb(FragmentActivity activity, String tag) {
+        super(activity, tag);
+        mTab = activity.getActionBar().newTab();
+    }
+
+    @Override
+    public CompatTab setText(int resId) {
+        mTab.setText(resId);
+        return this;
+    }
+
+    @Override
+    public CompatTab setIcon(int resId) {
+        mTab.setIcon(resId);
+        return this;
+    }
+
+    @Override
+    public CompatTab setTabListener(CompatTabListener callback) {
+        mCallback = callback;
+        mTab.setTabListener(this);
+        return this;
+    }
+
+    @Override
+    public CharSequence getText() {
+        return mTab.getText();
+    }
+
+    @Override
+    public Drawable getIcon() {
+        return mTab.getIcon();
+    }
+
+    @Override
+    public Object getTab() {
+        return mTab;
+    }
+
+    @Override
+    public CompatTabListener getCallback() {
+        return mCallback;
+    }
+
+    @Override
+    public void onTabReselected(Tab tab, android.app.FragmentTransaction f) {
+        FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
+        ft.disallowAddToBackStack();
+        mCallback.onTabReselected(this, ft);
+        ft.commit();
+    }
+
+    @Override
+    public void onTabSelected(Tab tab, android.app.FragmentTransaction f) {
+        FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
+        ft.disallowAddToBackStack();
+        mCallback.onTabSelected(this, ft);
+        ft.commit();
+    }
+
+    @Override
+    public void onTabUnselected(Tab arg0, android.app.FragmentTransaction f) {
+        FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
+        ft.disallowAddToBackStack();
+        mCallback.onTabUnselected(this, ft);
+        ft.commit();
+    }
+
+    @Override
+    public CompatTab setFragment(Fragment fragment) {
+        mFragment = fragment;
+        return this;
+    }
+
+    @Override
+    public Fragment getFragment() {
+        return mFragment;
+    }
+}

samples/training/TabCompat/src/com/example/android/tabcompat/lib/CompatTabListener.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.android.tabcompat.lib;
+
+import android.support.v4.app.FragmentTransaction;
+
+/**
+ * @see android.app.ActionBar.TabListener
+ */
+public interface CompatTabListener {
+    /**
+     * @see android.app.ActionBar.TabListener#onTabSelected(
+     *android.app.ActionBar.Tab, android.app.FragmentTransaction)
+     */
+    public void onTabSelected(CompatTab tab, FragmentTransaction ft);
+
+    /**
+     * @see android.app.ActionBar.TabListener#onTabUnselected(
+     *android.app.ActionBar.Tab, android.app.FragmentTransaction)
+     */
+    public void onTabUnselected(CompatTab tab, FragmentTransaction ft);
+
+    /**
+     * @see android.app.ActionBar.TabListener#onTabReselected(
+     *android.app.ActionBar.Tab, android.app.FragmentTransaction)
+     */
+    public void onTabReselected(CompatTab tab, FragmentTransaction ft);
+}

samples/training/TabCompat/src/com/example/android/tabcompat/lib/TabCompatActivity.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.android.tabcompat.lib;
+
+import com.example.android.tabcompat.lib.TabHelper;
+
+import android.os.Bundle;
+import android.support.v4.app.FragmentActivity;
+
+/**
+ * A base activity that defers tab functionality to a {@link TabHelper}.
+ *
+ * When building an activity with tabs, extend this class in order to provide compatibility with API
+ * level 5 and above. Using this class along with the {@link TabHelper} and {@link com.example.android.tabcompat.lib.CompatTab}
+ * classes, you can build a tab UI that's built using the {@link android.app.ActionBar} on
+ * Honeycomb+ and the {@link android.widget.TabWidget} on all older versions.
+ *
+ * The {@link TabHelper} APIs obfuscate all the compatibility work for you.
+ */
+public abstract class TabCompatActivity extends FragmentActivity {
+
+    TabHelper mTabHelper;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        mTabHelper = TabHelper.createInstance(this);
+    }
+
+    @Override
+    protected void onSaveInstanceState(Bundle outState) {
+        super.onSaveInstanceState(outState);
+        mTabHelper.onSaveInstanceState(outState);
+    }
+
+    @Override
+    protected void onRestoreInstanceState(Bundle savedInstanceState) {
+        super.onRestoreInstanceState(savedInstanceState);
+        mTabHelper.onRestoreInstanceState(savedInstanceState);
+    }
+
+    /**
+     * Returns the {@link TabHelper} for this activity.
+     */
+    protected TabHelper getTabHelper() {
+        mTabHelper.setUp();
+        return mTabHelper;
+    }
+}

samples/training/TabCompat/src/com/example/android/tabcompat/lib/TabHelper.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.android.tabcompat.lib;
+
+import android.os.Build;
+import android.os.Bundle;
+import android.support.v4.app.FragmentActivity;
+
+/**
+ * Convenience helper to build a set of tabs for a {@link TabCompatActivity}. To use this class,
+ * extend {@link TabCompatActivity} and:
+ *
+ * Call {@link TabCompatActivity#getTabHelper()}, returning a {@link TabHelper}.
+ *
+ * Create a {@link CompatTabListener}.
+ *
+ * Call {@link TabHelper#newTab(String)} to create each tab.
+ *
+ * Call CompatTab.setText().setIcon().setTabListener() to set up your tabs.
+ *
+ * Call {@link TabHelper#addTab(CompatTab)} for each tab, and you're done.
+ */
+public abstract class TabHelper {
+
+    protected FragmentActivity mActivity;
+
+    protected TabHelper(FragmentActivity activity) {
+        mActivity = activity;
+    }
+
+    /**
+     * Factory method for creating TabHelper objects for a given activity. Depending on which device
+     * the app is running, either a basic helper or Honeycomb-specific helper will be returned.
+     * Don't call this yourself; the TabCompatActivity instantiates one. Instead call
+     * TabCompatActivity.getTabHelper().
+     */
+    public static TabHelper createInstance(FragmentActivity activity) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
+            return new TabHelperHoneycomb(activity);
+        } else {
+            return new TabHelperEclair(activity);
+        }
+    }
+
+    /**
+     * Create a new tab.
+     *
+     * @param tag A unique tag to associate with the tab and associated fragment
+     * @return CompatTab for the appropriate android version
+     */
+    public CompatTab newTab(String tag) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
+            return new CompatTabHoneycomb(mActivity, tag);
+        } else {
+            return new CompatTabEclair(mActivity, tag);
+        }
+    }
+
+    public abstract void addTab(CompatTab tab);
+
+    protected abstract void onSaveInstanceState(Bundle outState);
+
+    protected abstract void onRestoreInstanceState(Bundle savedInstanceState);
+
+    protected abstract void setUp();
+}

samples/training/TabCompat/src/com/example/android/tabcompat/lib/TabHelperEclair.java

@@ -0,0 +1,156 @@
+/*
+ * Copyright 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.android.tabcompat.lib;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentActivity;
+import android.support.v4.app.FragmentTransaction;
+import android.view.View;
+import android.widget.TabHost;
+import android.widget.TabHost.TabSpec;
+
+import java.util.HashMap;
+
+/**
+ * This is a helper class to build tabs on pre-Honeycomb. Call {@link
+ * TabCompatActivity#getTabHelper()} to get the generic instance for
+ * compatibility with other versions.
+ *
+ * It implements a generic mechanism for associating fragments with the tabs in a tab host.  It
+ * relies on a trick:  Normally a tab host has a simple API for supplying a View or Intent that each
+ * tab will show.  This is not sufficient for switching between fragments.  So instead we make the
+ * content part of the tab host 0dp high (it is not shown) and this supplies its own dummy view to
+ * show as the tab content.  It listens to changes in tabs, then passes the event back to the tab's
+ * callback interface so the activity can take care of switching to the correct fragment.
+ */
+public class TabHelperEclair extends TabHelper implements TabHost.OnTabChangeListener {
+
+    private final HashMap<String, CompatTab> mTabs = new HashMap<String, CompatTab>();
+    private TabHost mTabHost;
+    CompatTabListener mCallback;
+    CompatTab mLastTab;
+
+    protected TabHelperEclair(FragmentActivity activity) {
+        super(activity);
+        mActivity = activity;
+    }
+
+    @Override
+    protected void setUp() {
+        if (mTabHost == null) {
+            mTabHost = (TabHost) mActivity.findViewById(android.R.id.tabhost);
+            mTabHost.setup();
+            mTabHost.setOnTabChangedListener(this);
+        }
+    }
+
+    @Override
+    public void addTab(CompatTab tab) {
+        String tag = tab.getTag();
+        TabSpec spec;
+
+        if (tab.getIcon() != null) {
+            spec = mTabHost.newTabSpec(tag).setIndicator(tab.getText(), tab.getIcon());
+        } else {
+            spec = mTabHost.newTabSpec(tag).setIndicator(tab.getText());
+        }
+
+        spec.setContent(new DummyTabFactory(mActivity));
+
+        // Check to see if we already have a fragment for this tab, probably
+        // from a previously saved state.  If so, deactivate it, because our
+        // initial state is that a tab isn't shown.
+
+        Fragment fragment = mActivity.getSupportFragmentManager().findFragmentByTag(tag);
+        tab.setFragment(fragment);
+
+        if (fragment != null && !fragment.isDetached()) {
+            FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
+            ft.detach(fragment);
+            ft.commit();
+        }
+
+        mTabs.put(tag, tab);
+        mTabHost.addTab(spec);
+    }
+
+    /**
+     * Converts the basic "tab changed" event for TabWidget into the three possible events for
+     * CompatTabListener: selected, unselected, reselected.
+     */
+    @Override
+    public void onTabChanged(String tabId) {
+        CompatTab newTab = mTabs.get(tabId);
+        FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
+
+        if (mLastTab != newTab) {
+            if (mLastTab != null) {
+                if (mLastTab.getFragment() != null) {
+                    // Pass the unselected event back to the tab's CompatTabListener
+                    mLastTab.getCallback().onTabUnselected(mLastTab, ft);
+                }
+            }
+            if (newTab != null) {
+                // Pass the selected event back to the tab's CompatTabListener
+                newTab.getCallback().onTabSelected(newTab, ft);
+            }
+
+            mLastTab = newTab;
+        } else {
+            // Pass the re-selected event back to the tab's CompatTabListener
+            newTab.getCallback().onTabReselected(newTab, ft);
+        }
+
+        ft.commit();
+        mActivity.getSupportFragmentManager().executePendingTransactions();
+    }
+
+    @Override
+    protected void onSaveInstanceState(Bundle outState) {
+        // Save and restore the selected tab for rotations/restarts.
+        outState.putString("tab", mTabHost.getCurrentTabTag());
+    }
+
+    @Override
+    protected void onRestoreInstanceState(Bundle savedInstanceState) {
+        if (savedInstanceState != null) {
+            mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab"));
+        }
+    }
+
+    /**
+     * Backwards-compatibility mumbo jumbo
+     */
+    static class DummyTabFactory implements TabHost.TabContentFactory {
+
+        private final Context mContext;
+
+        public DummyTabFactory(Context context) {
+            mContext = context;
+        }
+
+        @Override
+        public View createTabContent(String tag) {
+            View v = new View(mContext);
+            v.setMinimumWidth(0);
+            v.setMinimumHeight(0);
+            return v;
+        }
+    }
+}

samples/training/TabCompat/src/com/example/android/tabcompat/lib/TabHelperHoneycomb.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.android.tabcompat.lib;
+
+import android.app.ActionBar;
+import android.os.Bundle;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentActivity;
+import android.support.v4.app.FragmentTransaction;
+
+/**
+ * Helper class to build tabs on Honeycomb. Call {@link TabCompatActivity#getTabHelper()}
+ * to get the generic instance for compatibility with older versions.
+ */
+public class TabHelperHoneycomb extends TabHelper {
+
+    ActionBar mActionBar;
+
+    protected TabHelperHoneycomb(FragmentActivity activity) {
+        super(activity);
+    }
+
+    @Override
+    protected void setUp() {
+        if (mActionBar == null) {
+            mActionBar = mActivity.getActionBar();
+            mActionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
+        }
+    }
+
+    @Override
+    public void addTab(CompatTab tab) {
+        String tag = tab.getTag();
+
+        // Check to see if we already have a fragment for this tab, probably
+        // from a previously saved state.  If so, deactivate it, because our
+        // initial state is that a tab isn't shown.
+
+        Fragment fragment = mActivity.getSupportFragmentManager().findFragmentByTag(tag);
+        tab.setFragment(fragment);
+
+        if (fragment != null && !fragment.isDetached()) {
+            FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
+            ft.detach(fragment);
+            ft.commit();
+        }
+
+        if (tab.getCallback() == null) {
+            throw new IllegalStateException("CompatTab must have a CompatTabListener");
+        }
+
+        // We know tab is a CompatTabHoneycomb instance, so its
+        // native tab object is an ActionBar.Tab.
+        mActionBar.addTab((ActionBar.Tab) tab.getTab());
+    }
+
+    @Override
+    protected void onSaveInstanceState(Bundle outState) {
+        int position = mActionBar.getSelectedTab().getPosition();
+        outState.putInt("tab_position", position);
+    }
+
+    @Override
+    protected void onRestoreInstanceState(Bundle savedInstanceState) {
+        int position = savedInstanceState.getInt("tab_position");
+        mActionBar.setSelectedNavigationItem(position);
+    }
+}