Home | History | Annotate | Download | only in lib 
      1 /*
      2  * Copyright 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *     http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.example.android.tabcompat.lib;
     18 
     19 import android.content.Context;
     20 import android.os.Bundle;
     21 import android.support.v4.app.Fragment;
     22 import android.support.v4.app.FragmentActivity;
     23 import android.support.v4.app.FragmentTransaction;
     24 import android.view.View;
     25 import android.widget.TabHost;
     26 import android.widget.TabHost.TabSpec;
     27 
     28 import java.util.HashMap;
     29 
     30 /**
     31  * This is a helper class to build tabs on pre-Honeycomb. Call {@link
     32  * TabCompatActivity#getTabHelper()} to get the generic instance for
     33  * compatibility with other versions.
     34  *
     35  * It implements a generic mechanism for associating fragments with the tabs in a tab host.  It
     36  * relies on a trick:  Normally a tab host has a simple API for supplying a View or Intent that each
     37  * tab will show.  This is not sufficient for switching between fragments.  So instead we make the
     38  * content part of the tab host 0dp high (it is not shown) and this supplies its own dummy view to
     39  * show as the tab content.  It listens to changes in tabs, then passes the event back to the tab's
     40  * callback interface so the activity can take care of switching to the correct fragment.
     41  */
     42 public class TabHelperEclair extends TabHelper implements TabHost.OnTabChangeListener {
     43 
     44     private final HashMap<String, CompatTab> mTabs = new HashMap<String, CompatTab>();
     45     private TabHost mTabHost;
     46     CompatTabListener mCallback;
     47     CompatTab mLastTab;
     48 
     49     protected TabHelperEclair(FragmentActivity activity) {
     50         super(activity);
     51         mActivity = activity;
     52     }
     53 
     54     @Override
     55     protected void setUp() {
     56         if (mTabHost == null) {
     57             mTabHost = (TabHost) mActivity.findViewById(android.R.id.tabhost);
     58             mTabHost.setup();
     59             mTabHost.setOnTabChangedListener(this);
     60         }
     61     }
     62 
     63     @Override
     64     public void addTab(CompatTab tab) {
     65         String tag = tab.getTag();
     66         TabSpec spec;
     67 
     68         if (tab.getIcon() != null) {
     69             spec = mTabHost.newTabSpec(tag).setIndicator(tab.getText(), tab.getIcon());
     70         } else {
     71             spec = mTabHost.newTabSpec(tag).setIndicator(tab.getText());
     72         }
     73 
     74         spec.setContent(new DummyTabFactory(mActivity));
     75 
     76         // Check to see if we already have a fragment for this tab, probably
     77         // from a previously saved state.  If so, deactivate it, because our
     78         // initial state is that a tab isn't shown.
     79 
     80         Fragment fragment = mActivity.getSupportFragmentManager().findFragmentByTag(tag);
     81         tab.setFragment(fragment);
     82 
     83         if (fragment != null && !fragment.isDetached()) {
     84             FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
     85             ft.detach(fragment);
     86             ft.commit();
     87         }
     88 
     89         mTabs.put(tag, tab);
     90         mTabHost.addTab(spec);
     91     }
     92 
     93     /**
     94      * Converts the basic "tab changed" event for TabWidget into the three possible events for
     95      * CompatTabListener: selected, unselected, reselected.
     96      */
     97     @Override
     98     public void onTabChanged(String tabId) {
     99         CompatTab newTab = mTabs.get(tabId);
    100         FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
    101 
    102         if (mLastTab != newTab) {
    103             if (mLastTab != null) {
    104                 if (mLastTab.getFragment() != null) {
    105                     // Pass the unselected event back to the tab's CompatTabListener
    106                     mLastTab.getCallback().onTabUnselected(mLastTab, ft);
    107                 }
    108             }
    109             if (newTab != null) {
    110                 // Pass the selected event back to the tab's CompatTabListener
    111                 newTab.getCallback().onTabSelected(newTab, ft);
    112             }
    113 
    114             mLastTab = newTab;
    115         } else {
    116             // Pass the re-selected event back to the tab's CompatTabListener
    117             newTab.getCallback().onTabReselected(newTab, ft);
    118         }
    119 
    120         ft.commit();
    121         mActivity.getSupportFragmentManager().executePendingTransactions();
    122     }
    123 
    124     @Override
    125     protected void onSaveInstanceState(Bundle outState) {
    126         // Save and restore the selected tab for rotations/restarts.
    127         outState.putString("tab", mTabHost.getCurrentTabTag());
    128     }
    129 
    130     @Override
    131     protected void onRestoreInstanceState(Bundle savedInstanceState) {
    132         if (savedInstanceState != null) {
    133             mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab"));
    134         }
    135     }
    136 
    137     /**
    138      * Backwards-compatibility mumbo jumbo
    139      */
    140     static class DummyTabFactory implements TabHost.TabContentFactory {
    141 
    142         private final Context mContext;
    143 
    144         public DummyTabFactory(Context context) {
    145             mContext = context;
    146         }
    147 
    148         @Override
    149         public View createTabContent(String tag) {
    150             View v = new View(mContext);
    151             v.setMinimumWidth(0);
    152             v.setMinimumHeight(0);
    153             return v;
    154         }
    155     }
    156 }
    157