Convert ViewPagerAdapter to kotlin and enforce that all tabs must have a title that comes from strings.xml

.idea/codeStyles/Project.xml

@@ -16,6 +16,7 @@
       <option name="NAMES_COUNT_TO_USE_IMPORT_ON_DEMAND" value="999" />
       <option name="IMPORT_LAYOUT_TABLE">
         <value>
+          <package name="" withSubpackages="true" static="false" module="true" />
           <package name="" withSubpackages="true" static="true" />
           <emptyLine />
           <package name="" withSubpackages="true" static="false" />

app/src/main/java/fr/free/nrw/commons/ViewPagerAdapter.java

@@ -1,68 +0,0 @@
-package fr.free.nrw.commons;
-
-import androidx.fragment.app.Fragment;
-import androidx.fragment.app.FragmentManager;
-import androidx.fragment.app.FragmentPagerAdapter;
-
-import java.util.ArrayList;
-import java.util.List;
-
-/**
- * This adapter will be used to display fragments in a ViewPager
- */
-public class ViewPagerAdapter extends FragmentPagerAdapter {
-    private List<Fragment> fragmentList = new ArrayList<>();
-    private List<String> fragmentTitleList = new ArrayList<>();
-
-    public ViewPagerAdapter(FragmentManager manager) {
-        super(manager);
-    }
-
-    /**
-     * Constructs a ViewPagerAdapter with a specified Fragment Manager and Fragment resume behavior.
-     *
-     * @param manager The FragmentManager
-     * @param behavior An integer which represents the behavior of non visible fragments. See
-     *                 FragmentPagerAdapter.java for options.
-     */
-    public ViewPagerAdapter(FragmentManager manager, int behavior) {
-        super(manager, behavior);
-    }
-
-    /**
-     * This method returns the fragment of the viewpager at a particular position
-     * @param position
-     */
-    @Override
-    public Fragment getItem(int position) {
-        return fragmentList.get(position);
-    }
-
-    /**
-     * This method returns the total number of fragments in the viewpager.
-     * @return size
-     */
-    @Override
-    public int getCount() {
-        return fragmentList.size();
-    }
-
-    /**
-     * This method sets the fragment and title list in the viewpager
-     * @param fragmentList List of all fragments to be displayed in the viewpager
-     * @param fragmentTitleList List of all titles of the fragments
-     */
-    public void setTabData(List<Fragment> fragmentList, List<String> fragmentTitleList) {
-        this.fragmentList = fragmentList;
-        this.fragmentTitleList = fragmentTitleList;
-    }
-
-    /**
-     * This method returns the title of the page at a particular position
-     * @param position
-     */
-    @Override
-    public CharSequence getPageTitle(int position) {
-        return fragmentTitleList.get(position);
-    }
-}

app/src/main/java/fr/free/nrw/commons/ViewPagerAdapter.kt

@@ -0,0 +1,44 @@
+package fr.free.nrw.commons
+
+import android.content.Context
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.FragmentManager
+import androidx.fragment.app.FragmentPagerAdapter
+import java.util.Locale
+
+/**
+ * This adapter will be used to display fragments in a ViewPager
+ */
+class ViewPagerAdapter : FragmentPagerAdapter {
+    private val context: Context
+    private var fragmentList: List<Fragment> = emptyList()
+    private var fragmentTitleList: List<String> = emptyList()
+
+    constructor(context: Context, manager: FragmentManager) : super(manager) {
+        this.context = context
+    }
+
+    constructor(context: Context, manager: FragmentManager, behavior: Int) : super(manager, behavior) {
+        this.context = context
+    }
+
+    override fun getItem(position: Int): Fragment = fragmentList[position]
+
+    override fun getPageTitle(position: Int): CharSequence = fragmentTitleList[position]
+
+    override fun getCount(): Int = fragmentList.size
+
+    fun setTabs(vararg titlesToFragments: Pair<Int, Fragment>) {
+        // Enforce that every title must come from strings.xml and all will consistently be uppercase
+        fragmentTitleList = titlesToFragments.map {
+            context.getString(it.first).uppercase(Locale.ROOT)
+        }
+        fragmentList = titlesToFragments.map { it.second }
+    }
+
+    companion object {
+        // Convenience method for Java callers, can be removed when everything is migrated
+        @JvmStatic
+        fun pairOf(first: Int, second: Fragment) = first to second
+    }
+}

app/src/main/java/fr/free/nrw/commons/category/CategoryDetailsActivity.kt

@@ -59,7 +59,7 @@ class CategoryDetailsActivity : BaseActivity(),
         val view = binding.root
         setContentView(view)
         supportFragmentManager = getSupportFragmentManager()
-        viewPagerAdapter = ViewPagerAdapter(supportFragmentManager)
+        viewPagerAdapter = ViewPagerAdapter(this, supportFragmentManager)
         binding.viewPager.adapter = viewPagerAdapter
         binding.viewPager.offscreenPageLimit = 2
         binding.tabLayout.setupWithViewPager(binding.viewPager)
@@ -83,8 +83,6 @@ class CategoryDetailsActivity : BaseActivity(),
      * Set the fragments according to the tab selected in the viewPager.
      */
     private fun setTabs() {
-        val fragmentList = mutableListOf<Fragment>()
-        val titleList = mutableListOf<String>()
         categoriesMediaFragment = CategoriesMediaFragment()
         val subCategoryListFragment = SubCategoriesFragment()
         val parentCategoriesFragment = ParentCategoriesFragment()
@@ -99,13 +97,12 @@ class CategoryDetailsActivity : BaseActivity(),
 
             viewModel.onCheckIfBookmarked(categoryName!!)
         }
-        fragmentList.add(categoriesMediaFragment)
-        titleList.add("MEDIA")
-        fragmentList.add(subCategoryListFragment)
-        titleList.add("SUBCATEGORIES")
-        fragmentList.add(parentCategoriesFragment)
-        titleList.add("PARENT CATEGORIES")
-        viewPagerAdapter.setTabData(fragmentList, titleList)
+
+        viewPagerAdapter.setTabs(
+            R.string.title_for_media to categoriesMediaFragment,
+            R.string.title_for_subcategories to subCategoryListFragment,
+            R.string.title_for_parent_categories to parentCategoriesFragment
+        )
         viewPagerAdapter.notifyDataSetChanged()
     }
 

app/src/main/java/fr/free/nrw/commons/explore/ExploreFragment.java

@@ -1,6 +1,7 @@
 package fr.free.nrw.commons.explore;
 
 import static androidx.viewpager.widget.ViewPager.SCROLL_STATE_IDLE;
+import static fr.free.nrw.commons.ViewPagerAdapter.pairOf;
 
 import android.os.Bundle;
 import android.view.LayoutInflater;
@@ -23,10 +24,12 @@ import fr.free.nrw.commons.kvstore.JsonKvStore;
 import fr.free.nrw.commons.theme.BaseActivity;
 import fr.free.nrw.commons.utils.ActivityUtils;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Locale;
 import javax.inject.Inject;
 import javax.inject.Named;
+import kotlin.Pair;
 
 public class ExploreFragment extends CommonsDaggerSupportFragment {
 
@@ -70,7 +73,7 @@ public class ExploreFragment extends CommonsDaggerSupportFragment {
         loadNearbyMapData();
         binding = FragmentExploreBinding.inflate(inflater, container, false);
 
-        viewPagerAdapter = new ViewPagerAdapter(getChildFragmentManager(),
+        viewPagerAdapter = new ViewPagerAdapter(requireContext(), getChildFragmentManager(),
             FragmentPagerAdapter.BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
 
         binding.viewPager.setAdapter(viewPagerAdapter);
@@ -111,9 +114,6 @@ public class ExploreFragment extends CommonsDaggerSupportFragment {
      * Sets the titles in the tabLayout and fragments in the viewPager
      */
     public void setTabs() {
-        List<Fragment> fragmentList = new ArrayList<>();
-        List<String> titleList = new ArrayList<>();
-
         Bundle featuredArguments = new Bundle();
         featuredArguments.putString("categoryName", FEATURED_IMAGES_CATEGORY);
 
@@ -133,19 +133,15 @@ public class ExploreFragment extends CommonsDaggerSupportFragment {
         featuredRootFragment = new ExploreListRootFragment(featuredArguments);
         mobileRootFragment = new ExploreListRootFragment(mobileArguments);
         mapRootFragment = new ExploreMapRootFragment(mapArguments);
-        fragmentList.add(featuredRootFragment);
-        titleList.add(getString(R.string.explore_tab_title_featured).toUpperCase(Locale.ROOT));
-
-        fragmentList.add(mobileRootFragment);
-        titleList.add(getString(R.string.explore_tab_title_mobile).toUpperCase(Locale.ROOT));
-
-        fragmentList.add(mapRootFragment);
-        titleList.add(getString(R.string.explore_tab_title_map).toUpperCase(Locale.ROOT));
 
         ((MainActivity) getActivity()).showTabs();
         ((BaseActivity) getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(false);
 
-        viewPagerAdapter.setTabData(fragmentList, titleList);
+        viewPagerAdapter.setTabs(
+            pairOf(R.string.explore_tab_title_featured, featuredRootFragment),
+            pairOf(R.string.explore_tab_title_mobile, mobileRootFragment),
+            pairOf(R.string.explore_tab_title_map, mapRootFragment)
+        );
         viewPagerAdapter.notifyDataSetChanged();
     }
 

app/src/main/java/fr/free/nrw/commons/explore/SearchActivity.java

@@ -1,5 +1,7 @@
 package fr.free.nrw.commons.explore;
 
+import static fr.free.nrw.commons.ViewPagerAdapter.pairOf;
+
 import android.os.Bundle;
 import android.text.TextUtils;
 import android.view.View;
@@ -26,11 +28,13 @@ import fr.free.nrw.commons.utils.FragmentUtils;
 import fr.free.nrw.commons.utils.ViewUtil;
 import io.reactivex.android.schedulers.AndroidSchedulers;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Date;
 import java.util.List;
 import java.util.Locale;
 import java.util.concurrent.TimeUnit;
 import javax.inject.Inject;
+import kotlin.Pair;
 import timber.log.Timber;
 
 /**
@@ -65,7 +69,7 @@ public class SearchActivity extends BaseActivity
         binding.toolbarSearch.setNavigationOnClickListener(v->onBackPressed());
         supportFragmentManager = getSupportFragmentManager();
         setSearchHistoryFragment();
-        viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
+        viewPagerAdapter = new ViewPagerAdapter(this, getSupportFragmentManager());
         binding.viewPager.setAdapter(viewPagerAdapter);
         binding.viewPager.setOffscreenPageLimit(2); // Because we want all the fragments to be alive
         binding.tabLayout.setupWithViewPager(binding.viewPager);
@@ -90,19 +94,15 @@ public class SearchActivity extends BaseActivity
      * Sets the titles in the tabLayout and fragments in the viewPager
      */
     public void setTabs() {
-        List<Fragment> fragmentList = new ArrayList<>();
-        List<String> titleList = new ArrayList<>();
         searchMediaFragment = new SearchMediaFragment();
         searchDepictionsFragment = new SearchDepictionsFragment();
         searchCategoryFragment= new SearchCategoryFragment();
-        fragmentList.add(searchMediaFragment);
-        titleList.add(getResources().getString(R.string.search_tab_title_media).toUpperCase(Locale.ROOT));
-        fragmentList.add(searchCategoryFragment);
-        titleList.add(getResources().getString(R.string.search_tab_title_categories).toUpperCase(Locale.ROOT));
-        fragmentList.add(searchDepictionsFragment);
-        titleList.add(getResources().getString(R.string.search_tab_title_depictions).toUpperCase(Locale.ROOT));
 
-        viewPagerAdapter.setTabData(fragmentList, titleList);
+        viewPagerAdapter.setTabs(
+            pairOf(R.string.search_tab_title_media, searchMediaFragment),
+            pairOf(R.string.search_tab_title_categories, searchCategoryFragment),
+            pairOf(R.string.search_tab_title_depictions, searchDepictionsFragment)
+        );
         viewPagerAdapter.notifyDataSetChanged();
         getCompositeDisposable().add(RxSearchView.queryTextChanges(binding.searchBox)
                 .takeUntil(RxView.detaches(binding.searchBox))

app/src/main/java/fr/free/nrw/commons/explore/depictions/WikidataItemDetailsActivity.java

@@ -1,5 +1,6 @@
 package fr.free.nrw.commons.explore.depictions;
 
+import static fr.free.nrw.commons.ViewPagerAdapter.pairOf;
 import static fr.free.nrw.commons.utils.UrlUtilsKt.handleWebUrl;
 
 import android.content.Context;
@@ -31,8 +32,10 @@ import io.reactivex.android.schedulers.AndroidSchedulers;
 import io.reactivex.disposables.CompositeDisposable;
 import io.reactivex.schedulers.Schedulers;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import javax.inject.Inject;
+import kotlin.Pair;
 
 /**
  * Activity to show depiction media, parent classes and child classes of depicted items in Explore
@@ -66,7 +69,7 @@ public class WikidataItemDetailsActivity extends BaseActivity implements MediaDe
         setContentView(binding.getRoot());
         compositeDisposable = new CompositeDisposable();
         supportFragmentManager = getSupportFragmentManager();
-        viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
+        viewPagerAdapter = new ViewPagerAdapter(this, getSupportFragmentManager());
         binding.viewPager.setAdapter(viewPagerAdapter);
         binding.viewPager.setOffscreenPageLimit(2);
         binding.tabLayout.setupWithViewPager(binding.viewPager);
@@ -105,8 +108,6 @@ public class WikidataItemDetailsActivity extends BaseActivity implements MediaDe
      * Set the fragments according to the tab selected in the viewPager.
      */
     private void setTabs() {
-        List<Fragment> fragmentList = new ArrayList<>();
-        List<String> titleList = new ArrayList<>();
         depictionImagesListFragment = new DepictedImagesFragment();
         ChildDepictionsFragment childDepictionsFragment = new ChildDepictionsFragment();
         ParentDepictionsFragment parentDepictionsFragment = new ParentDepictionsFragment();
@@ -120,13 +121,12 @@ public class WikidataItemDetailsActivity extends BaseActivity implements MediaDe
             parentDepictionsFragment.setArguments(arguments);
             childDepictionsFragment.setArguments(arguments);
         }
-        fragmentList.add(depictionImagesListFragment);
-        titleList.add(getResources().getString(R.string.title_for_media));
-        fragmentList.add(childDepictionsFragment);
-        titleList.add(getResources().getString(R.string.title_for_child_classes));
-        fragmentList.add(parentDepictionsFragment);
-        titleList.add(getResources().getString(R.string.title_for_parent_classes));
-        viewPagerAdapter.setTabData(fragmentList, titleList);
+
+        viewPagerAdapter.setTabs(
+            pairOf(R.string.title_for_media, depictionImagesListFragment),
+            pairOf(R.string.title_for_subcategories, childDepictionsFragment),
+            pairOf(R.string.title_for_parent_categories, parentDepictionsFragment)
+        );
         binding.viewPager.setOffscreenPageLimit(2);
         viewPagerAdapter.notifyDataSetChanged();
 

app/src/main/java/fr/free/nrw/commons/profile/ProfileActivity.kt

@@ -11,6 +11,7 @@ import android.view.View
 import android.widget.ImageView
 import android.widget.TextView
 import androidx.core.content.FileProvider
+import androidx.core.os.bundleOf
 import androidx.fragment.app.Fragment
 import fr.free.nrw.commons.R
 import fr.free.nrw.commons.ViewPagerAdapter
@@ -71,7 +72,7 @@ class ProfileActivity : BaseActivity() {
         title = userName
         shouldShowContributions = intent.getBooleanExtra(KEY_SHOULD_SHOW_CONTRIBUTIONS, false)
 
-        viewPagerAdapter = ViewPagerAdapter(supportFragmentManager)
+        viewPagerAdapter = ViewPagerAdapter(this, supportFragmentManager)
         binding.viewPager.adapter = viewPagerAdapter
         binding.tabLayout.setupWithViewPager(binding.viewPager)
         setTabs()
@@ -83,39 +84,23 @@ class ProfileActivity : BaseActivity() {
     }
 
     private fun setTabs() {
-        val fragmentList = mutableListOf<Fragment>()
-        val titleList = mutableListOf<String>()
-
-        // Add Achievements tab
         achievementsFragment = AchievementsFragment().apply {
-            arguments = Bundle().apply {
-                putString(KEY_USERNAME, userName)
-            }
+            arguments = bundleOf(KEY_USERNAME to userName)
         }
-        fragmentList.add(achievementsFragment)
-        titleList.add(resources.getString(R.string.achievements_tab_title).uppercase())
 
-        // Add Leaderboard tab
         leaderboardFragment = LeaderboardFragment().apply {
-            arguments = Bundle().apply {
-                putString(KEY_USERNAME, userName)
-            }
+            arguments = bundleOf(KEY_USERNAME to userName)
         }
-        fragmentList.add(leaderboardFragment)
-        titleList.add(resources.getString(R.string.leaderboard_tab_title).uppercase(Locale.ROOT))
 
-        // Add Contributions tab
         contributionsFragment = ContributionsFragment().apply {
-            arguments = Bundle().apply {
-                putString(KEY_USERNAME, userName)
-            }
-        }
-        contributionsFragment?.let {
-            fragmentList.add(it)
-            titleList.add(getString(R.string.contributions_fragment).uppercase(Locale.ROOT))
+            arguments = bundleOf(KEY_USERNAME to userName)
         }
 
-        viewPagerAdapter.setTabData(fragmentList, titleList)
+        viewPagerAdapter.setTabs(
+            R.string.achievements_tab_title to achievementsFragment,
+            R.string.leaderboard_tab_title to leaderboardFragment,
+            R.string.contributions_fragment to contributionsFragment!!
+        )
         viewPagerAdapter.notifyDataSetChanged()
     }
 

app/src/main/java/fr/free/nrw/commons/upload/UploadProgressActivity.kt

@@ -28,8 +28,6 @@ class UploadProgressActivity : BaseActivity() {
     @Inject
     lateinit var contributionDao: ContributionDao
 
-    val fragmentList: MutableList<Fragment> = ArrayList()
-    val titleList: MutableList<String> = ArrayList()
     var isPaused = true
     var isPendingIconsVisible = true
     var isErrorIconsVisisble = false
@@ -38,7 +36,7 @@ class UploadProgressActivity : BaseActivity() {
         super.onCreate(savedInstanceState)
         binding = ActivityUploadProgressBinding.inflate(layoutInflater)
         setContentView(binding.root)
-        viewPagerAdapter = ViewPagerAdapter(supportFragmentManager)
+        viewPagerAdapter = ViewPagerAdapter(this, supportFragmentManager)
         binding.uploadProgressViewPager.setAdapter(viewPagerAdapter)
         binding.uploadProgressViewPager.setId(R.id.upload_progress_view_pager)
         binding.uploadProgressTabLayout.setupWithViewPager(binding.uploadProgressViewPager)
@@ -81,11 +79,10 @@ class UploadProgressActivity : BaseActivity() {
         pendingUploadsFragment = PendingUploadsFragment()
         failedUploadsFragment = FailedUploadsFragment()
 
-        fragmentList.add(pendingUploadsFragment!!)
-        titleList.add(getString(R.string.pending))
-        fragmentList.add(failedUploadsFragment!!)
-        titleList.add(getString(R.string.failed))
-        viewPagerAdapter!!.setTabData(fragmentList, titleList)
+        viewPagerAdapter!!.setTabs(
+            R.string.pending to pendingUploadsFragment!!,
+            R.string.failed to failedUploadsFragment!!
+        )
         viewPagerAdapter!!.notifyDataSetChanged()
     }
 

app/src/main/res/values/strings.xml

@@ -617,6 +617,8 @@ Upload your first media by tapping on the add button.</string>
   <string name="title_for_media">MEDIA</string>
   <string name="title_for_child_classes">CHILD CLASSES</string>
   <string name="title_for_parent_classes">PARENT CLASSES</string>
+  <string name="title_for_subcategories">SUBCATEGORIES</string>
+  <string name="title_for_parent_categories">PARENT CATEGORIES</string>
 
   <string name="upload_nearby_place_found_title">Nearby Place Found</string>
   <string name="upload_nearby_place_found_description_plural">Are these pictures of %1$s?</string>