Reduce code duplication between pager adapters

app/src/main/java/org/nutritionfacts/dailydozen/adapter/DailyDozenPagerAdapter.java

@@ -1,37 +1,20 @@
 package org.nutritionfacts.dailydozen.adapter;
 
 import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
-import androidx.fragment.app.FragmentStatePagerAdapter;
 
 import org.nutritionfacts.dailydozen.fragment.DailyDozenFragment;
 import org.nutritionfacts.dailydozen.model.Day;
 
-public class DailyDozenPagerAdapter extends FragmentStatePagerAdapter {
-    private int numDaysSinceEpoch;
-
+public class DailyDozenPagerAdapter extends SynchronizedDatePagerAdapter {
     public DailyDozenPagerAdapter(@NonNull FragmentManager fm, int behavior) {
         super(fm, behavior);
-
-        this.numDaysSinceEpoch = Day.getNumDaysSinceEpoch();
     }
 
     @NonNull
     @Override
     public Fragment getItem(int position) {
         return DailyDozenFragment.newInstance(Day.getByOffsetFromEpoch(position));
     }
-
-    @Nullable
-    @Override
-    public CharSequence getPageTitle(int position) {
-        return Day.getTabTitleForDay(position);
-    }
-
-    @Override
-    public int getCount() {
-        return numDaysSinceEpoch;
-    }
 }

app/src/main/java/org/nutritionfacts/dailydozen/adapter/SynchronizedDatePagerAdapter.java

@@ -0,0 +1,29 @@
+package org.nutritionfacts.dailydozen.adapter;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.fragment.app.FragmentManager;
+import androidx.fragment.app.FragmentStatePagerAdapter;
+
+import org.nutritionfacts.dailydozen.model.Day;
+
+public abstract class SynchronizedDatePagerAdapter extends FragmentStatePagerAdapter {
+    protected int numDaysSinceEpoch;
+
+    public SynchronizedDatePagerAdapter(@NonNull FragmentManager fm, int behavior) {
+        super(fm, behavior);
+
+        numDaysSinceEpoch = Day.getNumDaysSinceEpoch();
+    }
+
+    @Override
+    public int getCount() {
+        return numDaysSinceEpoch;
+    }
+
+    @Nullable
+    @Override
+    public CharSequence getPageTitle(int position) {
+        return Day.getTabTitleForDay(position);
+    }
+}

app/src/main/java/org/nutritionfacts/dailydozen/adapter/TweaksPagerAdapter.java

@@ -1,37 +1,20 @@
 package org.nutritionfacts.dailydozen.adapter;
 
 import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
-import androidx.fragment.app.FragmentStatePagerAdapter;
 
 import org.nutritionfacts.dailydozen.fragment.TweaksFragment;
 import org.nutritionfacts.dailydozen.model.Day;
 
-public class TweaksPagerAdapter extends FragmentStatePagerAdapter {
-    private int numDaysSinceEpoch;
-
+public class TweaksPagerAdapter extends SynchronizedDatePagerAdapter {
     public TweaksPagerAdapter(@NonNull FragmentManager fm, int behavior) {
         super(fm, behavior);
-
-        numDaysSinceEpoch = Day.getNumDaysSinceEpoch();
     }
 
     @NonNull
     @Override
     public Fragment getItem(int position) {
         return TweaksFragment.newInstance(Day.getByOffsetFromEpoch(position));
     }
-
-    @Nullable
-    @Override
-    public CharSequence getPageTitle(int position) {
-        return Day.getTabTitleForDay(position);
-    }
-
-    @Override
-    public int getCount() {
-        return numDaysSinceEpoch;
-    }
 }