6.7. CannonGameFragment Subclass of Fragment

Class CannonGameFragment (Fig. 6.6) overrides four Fragment methods:

• onCreateView (lines 17–28)—As you learned in Section 5.3.3, this method is called after a Fragment’s onCreate method to build and return a View containing the Fragment’s GUI. Lines 22–23 inflate the GUI. Line 26 gets a reference to the CannonGameFragment’s CannonView so that we can call its methods.

• onActivityCreated (lines 31–38)—This method is called after the Fragment’s host Activity is created. Line 37 calls the Activity’s setVolumeControlStream method to allow the game’s audio volume to be controlled by the device’s volume keys.

• onPause (lines 41–46)—When the MainActivity is sent to the background (and thus, paused), the CannonGameFragment’s method onPause executes. Line 45 calls the CannonView’s stopGame method (Section 6.8.11) to stop the game loop.

• onDestroy (lines 49–54)—When the MainActivity is destroyed, its onDestroy method calls the CannonGameFragment’s onDestroy. Line 46 calls the CannonView’s releaseResources method (Section 6.8.11) to release the sound resources.

Click here to view code image

 1   // CannonGameFragment.java
 2   // CannonGameFragment creates and manages a CannonView
 3   package com.deitel.cannongame;
 4
 5   import android.app.Fragment;
 6   import android.media.AudioManager;
 7   import android.os.Bundle;
 8   import android.view.LayoutInflater;
 9   import android.view.View;
10   import android.view.ViewGroup;
11
12   public class CannonGameFragment extends Fragment
13   {
14      private CannonView cannonView; // custom view to display the game
15
16      // called when Fragment's view needs to be created
17      @Override
18      public View onCreateView(LayoutInflater inflater, ViewGroup container,
19         Bundle savedInstanceState)
20      {
21         super.onCreateView(inflater, container, savedInstanceState);
22         View view =
23            inflater.inflate(R.layout.fragment_game, container, false );
24
25         // get the CannonView
26         cannonView = (CannonView) view.findViewById(R.id.cannonView);
27         return view;
28      }
29
30      // set up volume control once Activity is created
31      @Override
32      public void onActivityCreated(Bundle savedInstanceState)
33      {
34         super.onActivityCreated(savedInstanceState);
35
36         // allow volume keys to set game volume
37         getActivity().setVolumeControlStream(AudioManager.STREAM_MUSIC);
38      }
39
40      // when MainActivity is paused, CannonGameFragment terminates the game
41      @Override
42      public void onPause()
43      {
44         super.onPause();
45         cannonView.stopGame(); // terminates the game
46      }
47
48      // when MainActivity is paused, CannonGameFragment releases resources
49      @Override
50      public void onDestroy()
51      {
52         super.onDestroy();
53         cannonView.releaseResources();
54      }
55   } // end class CannonGameFragment

Fig. 6.6 | CannonGameFragment creates and manages a CannonView.