Switch to ViewPager2 (got a deprecation warning for ViewPager)

app/build.gradle

@@ -5,7 +5,7 @@ android {
 
     defaultConfig {
         applicationId "atorch.statspuzzles"
-        minSdkVersion 16
+        minSdkVersion 19
         targetSdkVersion 34
         versionCode 32
         versionName "4.0"
@@ -35,6 +35,7 @@ dependencies {
     implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
     implementation 'androidx.navigation:navigation-fragment:2.5.3'
     implementation 'androidx.navigation:navigation-ui:2.5.3'
+    implementation 'androidx.viewpager2:viewpager2:1.1.0'
     testImplementation 'junit:junit:4.13.2'
     androidTestImplementation 'androidx.test.ext:junit:1.1.5'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'

app/src/androidTest/java/atorch/statspuzzles/PuzzleSelectionTest.java

@@ -8,6 +8,7 @@
 import androidx.test.espresso.assertion.ViewAssertions;
 import androidx.test.espresso.matcher.ViewMatchers;
 import static androidx.test.espresso.action.ViewActions.click;
+import static androidx.test.espresso.action.ViewActions.swipeLeft;
 
 import org.junit.Rule;
 import org.junit.Test;
@@ -34,4 +35,15 @@ public void easyPuzzlesButton_loadsEasyPuzzles() {
         Espresso.onView(ViewMatchers.withText(context.getString(R.string.puzzle, 1)))
                 .check(ViewAssertions.matches(ViewMatchers.isDisplayed()));
     }
+
+    @Test
+    public void swipeHorizontally_showsNextPuzzle() {
+        Context context = InstrumentationRegistry.getInstrumentation().getTargetContext();
+        Espresso.onView(ViewMatchers.withText(context.getString(R.string.button_level_1))).perform(click());
+        Espresso.onView(ViewMatchers.withText(context.getString(R.string.puzzle, 1)))
+                .check(ViewAssertions.matches(ViewMatchers.isDisplayed()));
+        Espresso.onView(ViewMatchers.withId(R.id.pager)).perform(swipeLeft());
+        Espresso.onView(ViewMatchers.withText(context.getString(R.string.puzzle, 2)))
+                .check(ViewAssertions.matches(ViewMatchers.isDisplayed()));
+    }
 }

app/src/main/java/atorch/statspuzzles/SolvePuzzle.java

@@ -21,21 +21,26 @@
 import android.widget.TextView;
 import android.widget.Toast;
 
+import androidx.annotation.NonNull;
 import androidx.appcompat.app.ActionBar;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.ShareActionProvider;
 import androidx.core.view.MenuItemCompat;
 import androidx.fragment.app.Fragment;
+import androidx.fragment.app.FragmentActivity;
 import androidx.fragment.app.FragmentManager;
 import androidx.fragment.app.FragmentPagerAdapter;
-import androidx.viewpager.widget.ViewPager;
 
 import org.mariuszgromada.math.mxparser.Expression;
 
 import java.math.BigDecimal;
 import java.math.RoundingMode;
 import java.util.Random;
 
+import androidx.viewpager2.adapter.FragmentStateAdapter;
+import androidx.viewpager2.widget.ViewPager2;
+
+
 public class SolvePuzzle extends AppCompatActivity {
     // Following example at https://developer.android.com/training/sharing/shareaction.html
     private ShareActionProvider mShareActionProvider;
@@ -44,7 +49,8 @@ public class SolvePuzzle extends AppCompatActivity {
     public static final String LEVEL = "atorch.statspuzzles.LEVEL";
     private static final int roundingScale = 4;
 
-    private ViewPager puzzlePager;  // Displays puzzles one at a time
+    // Displays puzzles one at a time
+    private ViewPager2 puzzlePager;
 
     private int level;
 
@@ -64,18 +70,14 @@ public void onCreate(Bundle savedInstanceState) {
             level = intent.getIntExtra(PuzzleSelection.LEVEL, 0);
         }
 
-        FragmentManager fragmentManager = getSupportFragmentManager();
-
         res = new Res(getResources());
         puzzlePager = findViewById(R.id.pager);
-        puzzlePager.setAdapter(new AppSectionsPagerAdapter(fragmentManager, level, res));
+        puzzlePager.setAdapter(new AppSectionsPagerAdapter(this, level, res));
 
-        puzzlePager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
-            @Override public void onPageScrollStateChanged(int arg0) {
-            }
-            @Override public void onPageScrolled(int arg0, float arg1, int arg2) {
-            }
-            @Override public void onPageSelected(int puzzleIndex) {
+        puzzlePager.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
+            @Override
+            public void onPageSelected(int puzzleIndex) {
+                super.onPageSelected(puzzleIndex);
                 prepareSharePuzzle(res.getPuzzle(level, puzzleIndex));
             }
         });
@@ -209,30 +211,31 @@ String getFirstCongratulation(int level) {
         }
     }
 
-    public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {
+    public static class AppSectionsPagerAdapter extends FragmentStateAdapter {
 
         private final int level;
         private final Res res;
 
-        public AppSectionsPagerAdapter(FragmentManager fm, int level, Res res) {
-            super(fm);
+        public AppSectionsPagerAdapter(@NonNull FragmentActivity fa, int level, Res res) {
+            super(fa);
             this.level = level;
             this.res = res;
         }
 
+        @NonNull
         @Override
-        public Fragment getItem(int puzzleIndex) {
+        public Fragment createFragment(int puzzleIndex) {
             Fragment fragment = new SolvePuzzleFragment();
             Bundle args = new Bundle();
             args.putInt(LEVEL, level);
             args.putInt(PUZZLE_INDEX, puzzleIndex);
-
             fragment.setArguments(args);
             return fragment;
         }
 
+
         @Override
-        public int getCount() {
+        public int getItemCount() {
             return res.getPuzzleCount(level);
         }
     }
@@ -241,8 +244,6 @@ public static class SolvePuzzleFragment extends Fragment {
 
         private int level;
         private int puzzleIndex;
-        private double correctAnswer;
-        private ViewPager mViewPager;
         private Res res;
 
         @Override
@@ -277,8 +278,6 @@ public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle sa
             submitButton.setOnClickListener(this::onSubmit);
 
             String answer = res.getAnswer(level, puzzleIndex);
-            Expression correctAnswerExpression = new Expression(answer);
-            correctAnswer = correctAnswerExpression.calculate();  // This needs to always parse correctly!
 
             EditText user_answer = rootView.findViewById(R.id.user_answer);
             SharedPreferences preferences = getActivity().getSharedPreferences("atorch.statspuzzles.data", Context.MODE_PRIVATE);
@@ -291,7 +290,9 @@ public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle sa
                 user_answer.setText(answer);
                 // Show approx equal for correct answer
                 TextView answerApprox = rootView.findViewById(R.id.answerApprox);
-                BigDecimal bd = new BigDecimal(correctAnswer).setScale(roundingScale, RoundingMode.HALF_EVEN);
+                Expression correctAnswerExpression = new Expression(answer);
+                double correctAnswerValue = correctAnswerExpression.calculate();
+                BigDecimal bd = new BigDecimal(correctAnswerValue).setScale(roundingScale, RoundingMode.HALF_EVEN);
                 answerApprox.setText(getString(R.string.approximate_result, bd));
             }
 
@@ -395,7 +396,7 @@ public void openCongratulationsAlert(View view) {
             editor.commit();
 
             AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
-            mViewPager = view.getRootView().findViewById(R.id.pager);
+            ViewPager2 viewPager = view.getRootView().findViewById(R.id.pager);
 
             int nPuzzles = res.getPuzzleCount(level);
             boolean solvedAllPuzzles = puzzles_solved >= nPuzzles;
@@ -408,7 +409,7 @@ public void openCongratulationsAlert(View view) {
                             if (next_puzzleIndex >= nPuzzles) {
                                 next_puzzleIndex = 0;
                             }
-                            mViewPager.setCurrentItem(next_puzzleIndex);
+                            viewPager.setCurrentItem(next_puzzleIndex);
                             dialog.cancel();
                         }
                 );

app/src/main/res/layout/activity_solve_puzzle.xml

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.viewpager.widget.ViewPager
+<androidx.viewpager2.widget.ViewPager2
     android:id="@+id/pager"
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent">
 
-</androidx.viewpager.widget.ViewPager>
+</androidx.viewpager2.widget.ViewPager2>