- Improved SlidingTabLayout to properly handle adapter change and refresh automatically on dataset changed.

- Fixed memory leak caused by keeping the PagerAdapter around after the view hierarchy has been destroyed.

app/src/main/java/be/digitalia/fosdem/fragments/LiveFragment.java

@@ -9,26 +9,19 @@ import android.support.v4.view.ViewPager;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
-import be.digitalia.fosdem.R;
 
 import com.example.android.common.view.SlidingTabLayout;
 
+import be.digitalia.fosdem.R;
+
 public class LiveFragment extends Fragment {
 
-	private LivePagerAdapter livePagerAdapter;
-
-	@Override
-	public void onCreate(Bundle savedInstanceState) {
-		super.onCreate(savedInstanceState);
-		livePagerAdapter = new LivePagerAdapter(getChildFragmentManager(), getResources());
-	}
-
 	@Override
 	public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
 		View view = inflater.inflate(R.layout.fragment_live, container, false);
 
 		ViewPager pager = (ViewPager) view.findViewById(R.id.pager);
-		pager.setAdapter(livePagerAdapter);
+		pager.setAdapter(new LivePagerAdapter(getChildFragmentManager(), getResources()));
 		SlidingTabLayout slidingTabs = (SlidingTabLayout) view.findViewById(R.id.sliding_tabs);
 		slidingTabs.setViewPager(pager);
 

app/src/main/java/be/digitalia/fosdem/fragments/TracksFragment.java

@@ -33,19 +33,18 @@ public class TracksFragment extends Fragment implements LoaderCallbacks<List<Day
 		View emptyView;
 		ViewPager pager;
 		SlidingTabLayout slidingTabs;
+		DaysAdapter daysAdapter;
 	}
 
 	private static final int DAYS_LOADER_ID = 1;
 	private static final String PREF_CURRENT_PAGE = "tracks_current_page";
 
-	private DaysAdapter daysAdapter;
 	private ViewHolder holder;
 	private int savedCurrentPage = -1;
 
 	@Override
 	public void onCreate(Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
-		daysAdapter = new DaysAdapter(getChildFragmentManager());
 
 		if (savedInstanceState == null) {
 			// Restore the current page from preferences
@@ -62,6 +61,7 @@ public class TracksFragment extends Fragment implements LoaderCallbacks<List<Day
 		holder.emptyView = view.findViewById(android.R.id.empty);
 		holder.pager = (ViewPager) view.findViewById(R.id.pager);
 		holder.slidingTabs = (SlidingTabLayout) view.findViewById(R.id.sliding_tabs);
+		holder.daysAdapter = new DaysAdapter(getChildFragmentManager());
 
 		return view;
 	}
@@ -131,20 +131,19 @@ public class TracksFragment extends Fragment implements LoaderCallbacks<List<Day
 
 	@Override
 	public void onLoadFinished(Loader<List<Day>> loader, List<Day> data) {
-		daysAdapter.setDays(data);
+		holder.daysAdapter.setDays(data);
 
-		final int totalPages = daysAdapter.getCount();
+		final int totalPages = holder.daysAdapter.getCount();
 		if (totalPages == 0) {
 			holder.contentView.setVisibility(View.GONE);
 			holder.emptyView.setVisibility(View.VISIBLE);
-			holder.pager.clearOnPageChangeListeners();
 		} else {
 			holder.contentView.setVisibility(View.VISIBLE);
 			holder.emptyView.setVisibility(View.GONE);
 			if (holder.pager.getAdapter() == null) {
-				holder.pager.setAdapter(daysAdapter);
+				holder.pager.setAdapter(holder.daysAdapter);
-			}
 				holder.slidingTabs.setViewPager(holder.pager);
+			}
 			if (savedCurrentPage != -1) {
 				holder.pager.setCurrentItem(Math.min(savedCurrentPage, totalPages - 1), false);
 				savedCurrentPage = -1;

app/src/main/java/com/example/android/common/view/SlidingTabLayout.java

@@ -20,6 +20,7 @@ package com.example.android.common.view;
 import android.content.Context;
 import android.content.res.ColorStateList;
 import android.content.res.TypedArray;
+import android.database.DataSetObserver;
 import android.graphics.Typeface;
 import android.os.Build;
 import android.support.annotation.ColorInt;
@@ -59,6 +60,9 @@ public class SlidingTabLayout extends HorizontalScrollView {
 	private ColorStateList mTextColor;
 
 	private ViewPager mViewPager;
+	private PagerAdapter mAdapter;
+	private final InternalViewPagerListener mPageChangeListener = new InternalViewPagerListener();
+	private final PagerAdapterObserver mPagerAdapterObserver = new PagerAdapterObserver();
 
 	private TabListener mTabListener;
 
@@ -148,18 +152,32 @@ public class SlidingTabLayout extends HorizontalScrollView {
 	}
 
 	/**
-	 * Sets the associated view pager. Note that the assumption here is that the pager content
+	 * Sets the associated view pager. The ViewPager must have an adapter set.
-	 * (number of tabs and tab titles) does not change after this call has been made.
+	 * The SlidingTabLayout will then listen for changes and update the tabs automatically.
 	 */
 	public void setViewPager(ViewPager viewPager) {
-		mViewPager = viewPager;
+		if (mViewPager != null) {
+			mViewPager.removeOnPageChangeListener(mPageChangeListener);
+			mAdapter.unregisterDataSetObserver(mPagerAdapterObserver);
+		}
 		if (viewPager != null) {
-			viewPager.addOnPageChangeListener(new InternalViewPagerListener());
+			PagerAdapter adapter = viewPager.getAdapter();
+			if (adapter == null) {
+				throw new IllegalArgumentException("ViewPager does not have a PagerAdapter set");
+			}
+			mViewPager = viewPager;
+			mAdapter = adapter;
+			mPageChangeListener.reset();
+			viewPager.addOnPageChangeListener(mPageChangeListener);
+			adapter.registerDataSetObserver(mPagerAdapterObserver);
+		} else {
+			mViewPager = null;
+			mAdapter = null;
 		}
 		notifyDataSetChanged();
 	}
 
-	public void notifyDataSetChanged() {
+	private void notifyDataSetChanged() {
 		mTabStrip.removeAllViews();
 		if (mViewPager != null) {
 			populateTabStrip();
@@ -167,8 +185,7 @@ public class SlidingTabLayout extends HorizontalScrollView {
 	}
 
 	private void populateTabStrip() {
-		final PagerAdapter adapter = mViewPager.getAdapter();
+		final int adapterCount = mAdapter.getCount();
-		final int adapterCount = adapter.getCount();
 		final View.OnClickListener tabClickListener = new TabClickListener();
 		final LayoutInflater inflater = LayoutInflater.from(getContext());
 		final int currentItem = mViewPager.getCurrentItem();
@@ -203,7 +220,7 @@ public class SlidingTabLayout extends HorizontalScrollView {
 				lp.weight = 1;
 			}
 
-			tabTitleView.setText(adapter.getPageTitle(i));
+			tabTitleView.setText(mAdapter.getPageTitle(i));
 			tabView.setFocusable(true);
 			tabView.setOnClickListener(tabClickListener);
 
@@ -270,6 +287,22 @@ public class SlidingTabLayout extends HorizontalScrollView {
 				mTabStrip.getChildAt(i).setSelected(position == i);
 			}
 		}
+
+		public void reset() {
+			mScrollState = ViewPager.SCROLL_STATE_IDLE;
+		}
+	}
+
+	private class PagerAdapterObserver extends DataSetObserver {
+		@Override
+		public void onChanged() {
+			notifyDataSetChanged();
+		}
+
+		@Override
+		public void onInvalidated() {
+			notifyDataSetChanged();
+		}
 	}
 
 	private class TabClickListener implements View.OnClickListener {