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      1 /*
      2  * Copyright (C) 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 package com.example.android.fragments;
     17 
     18 import android.os.Bundle;
     19 import android.support.v4.app.FragmentActivity;
     20 import android.support.v4.app.FragmentTransaction;
     21 
     22 public class MainActivity extends FragmentActivity
     23         implements HeadlinesFragment.OnHeadlineSelectedListener {
     24 
     25     /** Called when the activity is first created. */
     26     @Override
     27     public void onCreate(Bundle savedInstanceState) {
     28         super.onCreate(savedInstanceState);
     29         setContentView(R.layout.news_articles);
     30 
     31         // Check whether the activity is using the layout version with
     32         // the fragment_container FrameLayout. If so, we must add the first fragment
     33         if (findViewById(R.id.fragment_container) != null) {
     34 
     35             // However, if we're being restored from a previous state,
     36             // then we don't need to do anything and should return or else
     37             // we could end up with overlapping fragments.
     38             if (savedInstanceState != null) {
     39                 return;
     40             }
     41 
     42             // Create an instance of ExampleFragment
     43             HeadlinesFragment firstFragment = new HeadlinesFragment();
     44 
     45             // In case this activity was started with special instructions from an Intent,
     46             // pass the Intent's extras to the fragment as arguments
     47             firstFragment.setArguments(getIntent().getExtras());
     48 
     49             // Add the fragment to the 'fragment_container' FrameLayout
     50             getSupportFragmentManager().beginTransaction()
     51                     .add(R.id.fragment_container, firstFragment).commit();
     52         }
     53     }
     54 
     55     public void onArticleSelected(int position) {
     56         // The user selected the headline of an article from the HeadlinesFragment
     57 
     58         // Capture the article fragment from the activity layout
     59         ArticleFragment articleFrag = (ArticleFragment)
     60                 getSupportFragmentManager().findFragmentById(R.id.article_fragment);
     61 
     62         if (articleFrag != null) {
     63             // If article frag is available, we're in two-pane layout...
     64 
     65             // Call a method in the ArticleFragment to update its content
     66             articleFrag.updateArticleView(position);
     67 
     68         } else {
     69             // If the frag is not available, we're in the one-pane layout and must swap frags...
     70 
     71             // Create fragment and give it an argument for the selected article
     72             ArticleFragment newFragment = new ArticleFragment();
     73             Bundle args = new Bundle();
     74             args.putInt(ArticleFragment.ARG_POSITION, position);
     75             newFragment.setArguments(args);
     76             FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
     77 
     78             // Replace whatever is in the fragment_container view with this fragment,
     79             // and add the transaction to the back stack so the user can navigate back
     80             transaction.replace(R.id.fragment_container, newFragment);
     81             transaction.addToBackStack(null);
     82 
     83             // Commit the transaction
     84             transaction.commit();
     85         }
     86     }
     87 }