Fix crash when attempting to connect via an Intent.

A race condition was introduced during refactor where the UI attempted
to update itself before a connection was made to the MediaSession when
connection information (by way of package name) was passed in via an
Intent.

The change makes it so the ViewPager is marked as GONE if the connection
hasn't yet been established. After a connection is then established, the
view is set to VISIBLE to trigger the updates.

Change-Id: Ie713a70df7474786688f286cbe0e49eaa63a971e

Author: nic0lette

mediacontroller/src/main/java/com/example/android/mediacontroller/MediaAppControllerActivity.java

@@ -126,6 +126,7 @@ public class MediaAppControllerActivity extends AppCompatActivity {
     private RatingUiHelper mRatingUiHelper;
     private CustomControlsAdapter mCustomControlsAdapter = new CustomControlsAdapter();
 
+    private ViewPager mViewPager;
     private Spinner mInputTypeView;
     private EditText mUriInput;
     private TextView mMediaInfoText;
@@ -163,6 +164,7 @@ protected void onCreate(Bundle savedInstanceState) {
         final Toolbar toolbar = findViewById(R.id.toolbar);
         setSupportActionBar(toolbar);
 
+        mViewPager = findViewById(R.id.view_pager);
         mInputTypeView = findViewById(R.id.input_type);
         mUriInput = findViewById(R.id.uri_id_query);
         mMediaInfoText = findViewById(R.id.media_info);
@@ -192,17 +194,19 @@ protected void onCreate(Bundle savedInstanceState) {
             // that will be taken care of by #connectToMediaBrowserPackage in handleIntent.
             setupMediaController();
             setupToolbar(mMediaAppDetails.appName, mMediaAppDetails.icon);
+        } else {
+            // Wait to show the ViewPager until connected.
+            mViewPager.setVisibility(View.GONE);
         }
 
-        final ViewPager viewPager = findViewById(R.id.view_pager);
         final int[] pages = {
                 R.id.prepare_play_page,
                 R.id.controls_page,
                 R.id.custom_controls_page,
         };
         // Simplify the adapter by not keeping track of creating/destroying off-screen views.
-        viewPager.setOffscreenPageLimit(pages.length);
-        viewPager.setAdapter(new PagerAdapter() {
+        mViewPager.setOffscreenPageLimit(pages.length);
+        mViewPager.setAdapter(new PagerAdapter() {
 
             @Override
             public int getCount() {
@@ -221,7 +225,7 @@ public Object instantiateItem(@NonNull ViewGroup container, int position) {
             }
         });
         final TabLayout pageIndicator = findViewById(R.id.page_indicator);
-        pageIndicator.setupWithViewPager(viewPager);
+        pageIndicator.setupWithViewPager(mViewPager);
 
         final RecyclerView customControlsList = findViewById(R.id.custom_controls_list);
         customControlsList.setLayoutManager(new LinearLayoutManager(this));
@@ -335,6 +339,9 @@ private void setupMediaController() {
             mCallback.onPlaybackStateChanged(mController.getPlaybackState());
             mCallback.onMetadataChanged(mController.getMetadata());
 
+            // Ensure views are visible.
+            mViewPager.setVisibility(View.VISIBLE);
+
             Log.d(TAG, "MediaControllerCompat created");
         } catch (RemoteException remoteException) {
             Log.e(TAG, "Failed to create MediaController from session token", remoteException);