samples/ApiDemos/src/com/example/android/apis/app/FragmentTabsFragment.java

/*
 * Copyright (C) 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.apis.app;

import java.util.HashMap;

import com.example.android.apis.R;

import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TabHost;

public class FragmentTabsFragment extends Fragment {
    TabHost mTabHost;
    TabManager mTabManager;
    String mCurrentTabTag;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_tabs_fragment, container, false);
        mTabHost = (TabHost)v.findViewById(android.R.id.tabhost);
        mTabHost.setup();

        mTabManager = new TabManager(getActivity(), getChildFragmentManager(),
                mTabHost, R.id.realtabcontent);

        mTabManager.addTab(mTabHost.newTabSpec("result").setIndicator("Result"),
                FragmentReceiveResult.ReceiveResultFragment.class, null);
        mTabManager.addTab(mTabHost.newTabSpec("contacts").setIndicator("Contacts"),
                LoaderCursor.CursorLoaderListFragment.class, null);
        mTabManager.addTab(mTabHost.newTabSpec("apps").setIndicator("Apps"),
                LoaderCustom.AppListFragment.class, null);
        mTabManager.addTab(mTabHost.newTabSpec("throttle").setIndicator("Throttle"),
                LoaderThrottle.ThrottledLoaderListFragment.class, null);

        return v;
    }

    @Override
    public void onViewStateRestored(Bundle savedInstanceState) {
        super.onViewStateRestored(savedInstanceState);
        if (savedInstanceState != null) {
            mCurrentTabTag = savedInstanceState.getString("tab");
        }
        mTabHost.setCurrentTabByTag(mCurrentTabTag);
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        // Need to remember the selected tab so that we can restore it if
        // we later re-create the views.
        mCurrentTabTag = mTabHost.getCurrentTabTag();
        mTabHost = null;
        mTabManager = null;
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putString("tab", mTabHost != null
                ? mTabHost.getCurrentTabTag() : mCurrentTabTag);
    }

    /**
     * This is a helper class that 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 the TabManager supplies its own dummy
     * view to show as the tab content.  It listens to changes in tabs, and takes
     * care of switch to the correct fragment shown in a separate content area
     * whenever the selected tab changes.
     */
    public static class TabManager implements TabHost.OnTabChangeListener {
        private final Context mContext;
        private final FragmentManager mManager;
        private final TabHost mTabHost;
        private final int mContainerId;
        private final HashMap<String, TabInfo> mTabs = new HashMap<String, TabInfo>();
        TabInfo mLastTab;

        static final class TabInfo {
            private final String tag;
            private final Class<?> clss;
            private final Bundle args;
            private Fragment fragment;

            TabInfo(String _tag, Class<?> _class, Bundle _args) {
                tag = _tag;
                clss = _class;
                args = _args;
            }
        }

        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;
            }
        }

        public TabManager(Context context, FragmentManager manager, TabHost tabHost,
                int containerId) {
            mContext = context;
            mManager = manager;
            mTabHost = tabHost;
            mContainerId = containerId;
            mTabHost.setOnTabChangedListener(this);
        }

        public void addTab(TabHost.TabSpec tabSpec, Class<?> clss, Bundle args) {
            tabSpec.setContent(new DummyTabFactory(mContext));
            String tag = tabSpec.getTag();

            TabInfo info = new TabInfo(tag, clss, args);

            // 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.
            info.fragment = mManager.findFragmentByTag(tag);
            if (info.fragment != null && !info.fragment.isDetached()) {
                FragmentTransaction ft = mManager.beginTransaction();
                ft.detach(info.fragment);
                ft.commit();
            }

            mTabs.put(tag, info);
            mTabHost.addTab(tabSpec);
        }

        @Override
        public void onTabChanged(String tabId) {
            TabInfo newTab = mTabs.get(tabId);
            if (mLastTab != newTab) {
                FragmentTransaction ft = mManager.beginTransaction();
                if (mLastTab != null) {
                    if (mLastTab.fragment != null) {
                        ft.detach(mLastTab.fragment);
                    }
                }
                if (newTab != null) {
                    if (newTab.fragment == null) {
                        newTab.fragment = Fragment.instantiate(mContext,
                                newTab.clss.getName(), newTab.args);
                        ft.add(mContainerId, newTab.fragment, newTab.tag);
                    } else {
                        ft.attach(newTab.fragment);
                    }
                }

                mLastTab = newTab;
                ft.commit();
                mManager.executePendingTransactions();
            }
        }
    }
}
//END_INCLUDE(complete)