[UI] Add lazy loading to fragments with view pager.

app/src/main/java/pl/szczodrzynski/edziennik/ui/modules/base/lazypager/LazyFragment.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) Kuba Szczodrzyński 2020-3-29.
+ */
+
+package pl.szczodrzynski.edziennik.ui.modules.base.lazypager
+
+import androidx.fragment.app.Fragment
+
+abstract class LazyFragment : Fragment() {
+    private var isPageCreated = false
+    var swipeRefreshLayoutCallback: ((isEnabled: Boolean) -> Unit)? = null
+
+    /**
+     * Called when the page is first shown, or if previous
+     * [onPageCreated] returned false
+     *
+     * @return true if the view is set up
+     * @return false if the setup failed. The method may be then called
+     * again, when page becomes visible.
+     */
+    abstract fun onPageCreated(): Boolean
+
+    internal fun createPage() {
+        if (!isPageCreated && isAdded) {
+            isPageCreated = onPageCreated()
+        }
+    }
+
+    override fun onResume() {
+        createPage()
+        super.onResume()
+    }
+}

app/src/main/java/pl/szczodrzynski/edziennik/ui/modules/base/lazypager/LazyPagerAdapter.kt

@@ -0,0 +1,13 @@
+/*
+ * Copyright (c) Kuba Szczodrzyński 2020-3-29.
+ */
+
+package pl.szczodrzynski.edziennik.ui.modules.base.lazypager
+
+import androidx.fragment.app.FragmentManager
+import androidx.fragment.app.FragmentStatePagerAdapter
+
+abstract class LazyPagerAdapter(fragmentManager: FragmentManager) : FragmentStatePagerAdapter(fragmentManager, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
+    var swipeRefreshLayoutCallback: ((isEnabled: Boolean) -> Unit)? = null
+    abstract override fun getItem(position: Int): LazyFragment
+}

app/src/main/java/pl/szczodrzynski/edziennik/ui/modules/base/lazypager/LazyViewPager.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) Kuba Szczodrzyński 2020-3-29.
+ */
+
+package pl.szczodrzynski.edziennik.ui.modules.base.lazypager
+
+import android.content.Context
+import android.util.AttributeSet
+import androidx.viewpager.widget.ViewPager
+
+class LazyViewPager @JvmOverloads constructor(
+        context: Context, attrs: AttributeSet? = null
+) : ViewPager(context, attrs) {
+    init {
+        addOnPageChangeListener(object : OnPageChangeListener {
+            override fun onPageScrollStateChanged(state: Int) {
+
+            }
+
+            override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {
+
+            }
+
+            override fun onPageSelected(position: Int) {
+                if (adapter is LazyPagerAdapter) {
+                    val fragment = adapter?.instantiateItem(this@LazyViewPager, position)
+                    val lazyFragment = fragment as? LazyFragment
+                    lazyFragment?.createPage()
+                }
+            }
+        })
+    }
+}

app/src/main/java/pl/szczodrzynski/edziennik/ui/modules/homework/HomeworkFragment.kt

@@ -68,6 +68,10 @@ class HomeworkFragment : Fragment() {
                 }))
 
         b.viewPager.adapter = MessagesFragment.Adapter(childFragmentManager).also { adapter ->
+            adapter.swipeRefreshLayoutCallback = { isEnabled ->
+                b.refreshLayout.isEnabled = isEnabled
+            }
+
             adapter.addFragment(HomeworkListFragment().also { fragment ->
                 fragment.arguments = Bundle().also {  args ->
                     args.putInt("homeworkDate", HomeworkDate.CURRENT)

app/src/main/java/pl/szczodrzynski/edziennik/ui/modules/homework/HomeworkListFragment.kt

@@ -4,17 +4,18 @@ import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
-import androidx.fragment.app.Fragment
 import androidx.lifecycle.Observer
 import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
 import pl.szczodrzynski.edziennik.App
 import pl.szczodrzynski.edziennik.MainActivity
 import pl.szczodrzynski.edziennik.data.db.entity.Event
 import pl.szczodrzynski.edziennik.databinding.HomeworkListBinding
 import pl.szczodrzynski.edziennik.getInt
+import pl.szczodrzynski.edziennik.ui.modules.base.lazypager.LazyFragment
 import pl.szczodrzynski.edziennik.utils.models.Date
 
-class HomeworkListFragment : Fragment() {
+class HomeworkListFragment : LazyFragment() {
 
     private lateinit var app: App
     private lateinit var activity: MainActivity
@@ -30,11 +31,7 @@ class HomeworkListFragment : Fragment() {
         return b.root
     }
 
-    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+    override fun onPageCreated(): Boolean {
-        // TODO check if app, activity, b can be null
-        if (!isAdded)
-            return
-
         if (arguments != null) {
             homeworkDate = arguments.getInt("homeworkDate", HomeworkDate.CURRENT)
         }
@@ -45,6 +42,16 @@ class HomeworkListFragment : Fragment() {
 
         b.homeworkView.setHasFixedSize(true)
         b.homeworkView.layoutManager = layoutManager
+        b.homeworkView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
+            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
+                if (recyclerView.canScrollVertically(-1)) {
+                    swipeRefreshLayoutCallback?.invoke(false)
+                }
+                if (!recyclerView.canScrollVertically(-1) && newState == RecyclerView.SCROLL_STATE_IDLE) {
+                    swipeRefreshLayoutCallback?.invoke(true)
+                }
+            }
+        })
 
         val filter = when(homeworkDate) {
             HomeworkDate.CURRENT -> "eventDate >= '" + Date.getToday().stringY_m_d + "'"
@@ -66,5 +73,6 @@ class HomeworkListFragment : Fragment() {
                         b.homeworkNoData.visibility = View.VISIBLE
                     }
                 })
+        return true
     }
 }

app/src/main/java/pl/szczodrzynski/edziennik/ui/modules/messages/MessagesFragment.kt

@@ -6,7 +6,6 @@ import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.FragmentManager
-import androidx.fragment.app.FragmentPagerAdapter
 import androidx.viewpager.widget.ViewPager
 import com.mikepenz.iconics.typeface.library.community.material.CommunityMaterial
 import pl.szczodrzynski.edziennik.App
@@ -14,8 +13,9 @@ import pl.szczodrzynski.edziennik.MainActivity
 import pl.szczodrzynski.edziennik.R
 import pl.szczodrzynski.edziennik.data.db.entity.Message
 import pl.szczodrzynski.edziennik.databinding.FragmentMessagesBinding
+import pl.szczodrzynski.edziennik.ui.modules.base.lazypager.LazyFragment
+import pl.szczodrzynski.edziennik.ui.modules.base.lazypager.LazyPagerAdapter
 import pl.szczodrzynski.edziennik.utils.Themes
-import java.util.*
 
 class MessagesFragment : Fragment() {
     companion object {
@@ -56,6 +56,10 @@ class MessagesFragment : Fragment() {
 
         b.viewPager.adapter = Adapter(childFragmentManager).also { adapter ->
 
+            adapter.swipeRefreshLayoutCallback = { isEnabled ->
+                b.refreshLayout.isEnabled = isEnabled
+            }
+
             adapter.addFragment(MessagesListFragment().also { fragment ->
                 fragment.arguments = Bundle().also { args ->
                     args.putInt("messageType", Message.TYPE_RECEIVED)
@@ -126,11 +130,11 @@ class MessagesFragment : Fragment() {
         }*/
     }
 
-    internal class Adapter(manager: FragmentManager) : FragmentPagerAdapter(manager) {
+    internal class Adapter(manager: FragmentManager) : LazyPagerAdapter(manager) {
-        private val mFragmentList = ArrayList<Fragment>()
+        private val mFragmentList = mutableListOf<LazyFragment>()
-        private val mFragmentTitleList = ArrayList<String>()
+        private val mFragmentTitleList = mutableListOf<String>()
 
-        override fun getItem(position: Int): Fragment {
+        override fun getItem(position: Int): LazyFragment {
             return mFragmentList[position]
         }
 
@@ -138,7 +142,8 @@ class MessagesFragment : Fragment() {
             return mFragmentList.size
         }
 
-        fun addFragment(fragment: Fragment, title: String) {
+        fun addFragment(fragment: LazyFragment, title: String) {
+            fragment.swipeRefreshLayoutCallback = this@Adapter.swipeRefreshLayoutCallback
             mFragmentList.add(fragment)
             mFragmentTitleList.add(title)
         }

app/src/main/java/pl/szczodrzynski/edziennik/ui/modules/messages/MessagesListFragment.java

@@ -10,11 +10,10 @@ import android.view.ViewGroup;
 import android.view.animation.Interpolator;
 
 import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 import androidx.databinding.DataBindingUtil;
-import androidx.fragment.app.Fragment;
 import androidx.interpolator.view.animation.FastOutSlowInInterpolator;
 import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -26,13 +25,15 @@ import pl.szczodrzynski.edziennik.data.db.entity.Message;
 import pl.szczodrzynski.edziennik.data.db.full.MessageFull;
 import pl.szczodrzynski.edziennik.data.db.full.MessageRecipientFull;
 import pl.szczodrzynski.edziennik.databinding.MessagesListBinding;
+import pl.szczodrzynski.edziennik.ui.modules.base.lazypager.LazyFragment;
 import pl.szczodrzynski.edziennik.utils.SimpleDividerItemDecoration;
 import pl.szczodrzynski.edziennik.utils.Themes;
 
 import static androidx.recyclerview.widget.RecyclerView.NO_POSITION;
+import static androidx.recyclerview.widget.RecyclerView.SCROLL_STATE_IDLE;
 import static pl.szczodrzynski.edziennik.utils.Utils.d;
 
-public class MessagesListFragment extends Fragment {
+public class MessagesListFragment extends LazyFragment {
 
     private App app = null;
     private MainActivity activity = null;
@@ -65,9 +66,9 @@ public class MessagesListFragment extends Fragment {
     }
 
     @Override
-    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
+    public boolean onPageCreated() {
         if (app == null || activity == null || b == null || !isAdded())
-            return;
+            return false;
 
         long messageId = -1;
         if (getArguments() != null) {
@@ -78,7 +79,7 @@ public class MessagesListFragment extends Fragment {
             args.putLong("messageId", messageId);
             getArguments().remove("messageId");
             activity.loadTarget(MainActivity.TARGET_MESSAGES_DETAILS, args);
-            return;
+            return false;
         }
 
         if (getArguments() != null) {
@@ -161,11 +162,24 @@ public class MessagesListFragment extends Fragment {
          // TODO ANIMATION
         //postponeEnterTransition();
 
-        viewParent = (ViewGroup) view.getParent();
+        viewParent = (ViewGroup) getView().getParent();
 
-        b.emailList.setLayoutManager(new LinearLayoutManager(view.getContext()));
+        b.emailList.setLayoutManager(new LinearLayoutManager(getView().getContext()));
-        b.emailList.addItemDecoration(new SimpleDividerItemDecoration(view.getContext()));
+        b.emailList.addItemDecoration(new SimpleDividerItemDecoration(getView().getContext()));
         b.emailList.setAdapter(messagesAdapter);
+        b.emailList.addOnScrollListener(new RecyclerView.OnScrollListener() {
+            @Override
+            public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
+                if (b.emailList.canScrollVertically(-1)) {
+                    if (getSwipeRefreshLayoutCallback() != null)
+                        getSwipeRefreshLayoutCallback().invoke(false);
+                }
+                if (!b.emailList.canScrollVertically(-1) && newState == SCROLL_STATE_IDLE) {
+                    if (getSwipeRefreshLayoutCallback() != null)
+                        getSwipeRefreshLayoutCallback().invoke(true);
+                }
+            }
+        });
 
         if (messageType == Message.TYPE_RECEIVED) {
             App.db.messageDao().getReceived(App.Companion.getProfileId()).observe(this, messageFulls -> {
@@ -215,7 +229,7 @@ public class MessagesListFragment extends Fragment {
             });
         }
 
-
+        return true;
     }
 
     private void createMessageList(List<MessageFull> messageFulls) {

app/src/main/java/pl/szczodrzynski/edziennik/ui/modules/timetable/TimetableDayFragment.kt

@@ -27,7 +27,7 @@ import pl.szczodrzynski.edziennik.data.db.full.LessonFull
 import pl.szczodrzynski.edziennik.databinding.TimetableLessonBinding
 import pl.szczodrzynski.edziennik.databinding.TimetableNoTimetableBinding
 import pl.szczodrzynski.edziennik.ui.dialogs.timetable.LessonDetailsDialog
-import pl.szczodrzynski.edziennik.ui.modules.base.PagerFragment
+import pl.szczodrzynski.edziennik.ui.modules.base.lazypager.LazyFragment
 import pl.szczodrzynski.edziennik.ui.modules.timetable.TimetableFragment.Companion.DEFAULT_END_HOUR
 import pl.szczodrzynski.edziennik.ui.modules.timetable.TimetableFragment.Companion.DEFAULT_START_HOUR
 import pl.szczodrzynski.edziennik.utils.ListenerScrollView
@@ -36,7 +36,7 @@ import java.util.*
 import kotlin.coroutines.CoroutineContext
 import kotlin.math.min
 
-class TimetableDayFragment : PagerFragment(), CoroutineScope {
+class TimetableDayFragment : LazyFragment(), CoroutineScope {
     companion object {
         private const val TAG = "TimetableDayFragment"
     }
@@ -104,9 +104,6 @@ class TimetableDayFragment : PagerFragment(), CoroutineScope {
     }
 
     override fun onPageCreated(): Boolean {
-        if (!isAdded)
-            return false
-
         // observe lesson database
         app.db.timetableDao().getForDate(App.profileId, date).observe(this, Observer { lessons ->
             launch {

app/src/main/java/pl/szczodrzynski/edziennik/ui/modules/timetable/TimetablePagerAdapter.kt

@@ -5,9 +5,9 @@
 package pl.szczodrzynski.edziennik.ui.modules.timetable
 
 import android.os.Bundle
-import androidx.fragment.app.Fragment
 import androidx.fragment.app.FragmentManager
-import androidx.fragment.app.FragmentStatePagerAdapter
+import pl.szczodrzynski.edziennik.ui.modules.base.lazypager.LazyFragment
+import pl.szczodrzynski.edziennik.ui.modules.base.lazypager.LazyPagerAdapter
 import pl.szczodrzynski.edziennik.utils.models.Date
 import pl.szczodrzynski.edziennik.utils.models.Week
 
@@ -16,7 +16,7 @@ class TimetablePagerAdapter(
         private val items: List<Date>,
         private val startHour: Int,
         private val endHour: Int
-) : FragmentStatePagerAdapter(fragmentManager, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
+) : LazyPagerAdapter(fragmentManager) {
     companion object {
         private const val TAG = "TimetablePagerAdapter"
     }
@@ -25,8 +25,9 @@ class TimetablePagerAdapter(
     private val weekStart by lazy { today.weekStart }
     private val weekEnd by lazy { weekStart.clone().stepForward(0, 0, 6) }
 
-    override fun getItem(position: Int): Fragment {
+    override fun getItem(position: Int): LazyFragment {
         return TimetableDayFragment().apply {
+            swipeRefreshLayoutCallback = this@TimetablePagerAdapter.swipeRefreshLayoutCallback
             arguments = Bundle().apply {
                 putInt("date", items[position].value)
                 putInt("startHour", startHour)

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

@@ -1,7 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <layout xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
-    xmlns:tools="http://schemas.android.com/tools">
 
     <pl.szczodrzynski.edziennik.utils.SwipeRefreshLayoutNoIndicator
         android:id="@+id/refreshLayout"
@@ -23,7 +22,7 @@
                 app:tabSelectedTextColor="?colorPrimary"
                 app:tabTextColor="?android:textColorPrimary" />
 
-            <androidx.viewpager.widget.ViewPager
+            <pl.szczodrzynski.edziennik.ui.modules.base.lazypager.LazyViewPager
                 android:id="@+id/viewPager"
                 android:layout_width="match_parent"
                 android:layout_height="match_parent"

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

@@ -21,7 +21,7 @@
                 app:tabSelectedTextColor="?colorPrimary"
                 app:tabTextColor="?android:textColorPrimary"/>
 
-            <androidx.viewpager.widget.ViewPager
+            <pl.szczodrzynski.edziennik.ui.modules.base.lazypager.LazyViewPager
                 android:id="@+id/viewPager"
                 android:layout_width="match_parent"
                 android:layout_height="match_parent"
@@ -29,4 +29,4 @@
         </LinearLayout>
 
     </pl.szczodrzynski.edziennik.utils.SwipeRefreshLayoutNoIndicator>
-</layout>
+</layout>

app/src/main/res/layout/fragment_timetable_v2.xml

@@ -28,7 +28,7 @@
                         android:id="@+id/tabLayout"
                         android:layout_width="match_parent"
                         android:layout_height="48dp"
-                        android:background="@color/colorSurface_6dp"
+                        android:background="@color/colorSurface_1dp"
                         app:rtl_tabIndicatorColor="?colorPrimary"
                         app:rtl_tabMaxWidth="300dp"
                         app:rtl_tabMinWidth="90dp"
@@ -40,7 +40,7 @@
                         app:rtl_tabTextAppearance="@style/rtl_RecyclerTabLayout.Tab" />
                 </com.google.android.material.appbar.AppBarLayout>
 
-                <androidx.viewpager.widget.ViewPager
+                <pl.szczodrzynski.edziennik.ui.modules.base.lazypager.LazyViewPager
                     android:id="@+id/viewPager"
                     android:layout_width="match_parent"
                     android:layout_height="match_parent"
@@ -94,4 +94,4 @@
 
         </FrameLayout>
     <!--</pl.szczodrzynski.edziennik.utils.SwipeRefreshLayoutNoIndicator>-->
-</layout>
+</layout>