Feature: pagination

.idea/deploymentTargetDropDown.xml

@@ -7,11 +7,11 @@
         <deviceKey>
           <Key>
             <type value="VIRTUAL_DEVICE_PATH" />
-            <value value="C:\Users\Admin\.android\avd\Pixel_2_API_30.avd" />
+            <value value="C:\Users\Admin\.android\avd\Pixel_7_Pro_API_30.avd" />
           </Key>
         </deviceKey>
       </Target>
     </targetSelectedWithDropDown>
-    <timeTargetWasSelectedWithDropDown value="2023-10-29T18:24:53.426357Z" />
+    <timeTargetWasSelectedWithDropDown value="2023-11-10T15:46:58.753378100Z" />
   </component>
 </project>

app/build.gradle.kts

@@ -83,4 +83,8 @@ dependencies {
     kapt("androidx.room:room-compiler:$room_version")
     implementation("androidx.room:room-ktx:$room_version")
     implementation("androidx.room:room-paging:$room_version")
+
+    //Paging
+    implementation ("androidx.paging:paging-compose:3.2.1")
+    implementation ("androidx.paging:paging-runtime:3.2.1")
 }

app/src/main/java/com/example/android_programming/composeui/Screens/AdminPanel/ChangePanel.kt

@@ -1,41 +1,62 @@
 package com.example.android_programming.composeui.Screens.AdminPanel
 
 import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.layout.wrapContentHeight
+import androidx.compose.foundation.layout.wrapContentSize
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.itemsIndexed
+import androidx.compose.material.CircularProgressIndicator
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import androidx.lifecycle.viewmodel.compose.viewModel
 import androidx.navigation.NavHostController
+import androidx.paging.LoadState
+import androidx.paging.compose.collectAsLazyPagingItems
+import androidx.paging.compose.itemKey
+import com.example.android_programming.model.Sneaker
 import com.example.android_programming.vmodel.AppViewModelProvider
 import com.example.android_programming.vmodel.SneakerViewModel
+import kotlinx.coroutines.delay
 
 @Composable
 fun ChangePanel(navHostController: NavHostController, sneakerViewModel: SneakerViewModel = viewModel(factory = AppViewModelProvider.Factory)) {
-    val list = sneakerViewModel.SneakerList.collectAsState(initial = emptyList()).value
+    val list = sneakerViewModel.sneakerList.collectAsLazyPagingItems()
+
     Column(
         modifier = Modifier
             .fillMaxSize()
             .background(Color.White)
-            .padding(16.dp)
+            .padding(16.dp, 80.dp)
     ) {
         Row {
             LazyColumn(
                 modifier = Modifier
                     .fillMaxSize()
             ) {
-                itemsIndexed(list
+                items(list.itemCount) { index ->
-                ){_, item->
+                    list[index]?.let { sneaker ->
-                    CardSneakerForChange(item = item, navHostController)
+                        CardSneakerForChange(item = sneaker, navController = navHostController)
                     }
                 }
             }
         }
     }
+}
+
+

app/src/main/java/com/example/android_programming/composeui/Screens/HomeScreen/HomeScreen.kt

@@ -28,13 +28,11 @@ import com.example.android_programming.vmodel.OrderViewModel
 
 @Composable
 fun HomeScreen(navHostController: NavHostController, orderViewModel: OrderViewModel) {
-    val context = LocalContext.current
-    val sneakers = remember { mutableStateListOf<Sneaker>() }
     Column(
         modifier = Modifier
             .fillMaxSize()
             .background(Color.White)
-            .verticalScroll(rememberScrollState())
+            /*.verticalScroll(rememberScrollState())*/
     ) {
         Row {
             // Поле для поиска

app/src/main/java/com/example/android_programming/composeui/Screens/HomeScreen/SneakerRecyclerView/RecyclerView.kt

@@ -1,17 +1,18 @@
 package com.example.android_programming.composeui.Screens.HomeScreen.SneakerRecyclerView
 
-import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxSize
-import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.grid.GridCells
+import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.collectAsState
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.dp
 import androidx.lifecycle.viewmodel.compose.viewModel
 import androidx.navigation.NavHostController
+import androidx.paging.compose.collectAsLazyPagingItems
+import androidx.paging.compose.itemKey
+import com.example.android_programming.model.Sneaker
 import com.example.android_programming.vmodel.AppViewModelProvider
 import com.example.android_programming.vmodel.OrderViewModel
 import com.example.android_programming.vmodel.SneakerViewModel
@@ -23,17 +24,18 @@ fun RecyclerView(navHostController : NavHostController, orderViewModel: OrderVie
             .fillMaxSize()
             .padding(bottom = 60.dp)
     ) {
-        val list = sneakerViewModel.SneakerList.collectAsState(initial = emptyList()).value
+        val sneakerLazyPagingItems = sneakerViewModel.sneakerList.collectAsLazyPagingItems()
-        val numColumns = 2
-        val chunkedList = list.chunked(numColumns)
 
-        for (chunkedListItem in chunkedList) {
+        LazyVerticalGrid(
-            Row(
+            columns = GridCells.Fixed(2)
-                horizontalArrangement = Arrangement.Center,
-                modifier = Modifier.fillMaxWidth()
         ) {
-                for (item in chunkedListItem) {
+            items(
-                    CardSneaker(item, navHostController, orderViewModel.selectedItems) { selectedItem ->
+                count = sneakerLazyPagingItems.itemCount,
+                key = sneakerLazyPagingItems.itemKey { sneaker -> sneaker.sneakerId!! }
+            ) { index: Int ->
+                val sneaker: Sneaker? = sneakerLazyPagingItems[index]
+                if (sneaker != null) {
+                    CardSneaker(sneaker, navHostController, orderViewModel.selectedItems) { selectedItem ->
                         orderViewModel.addSelectedItem(selectedItem)
                     }
                 }
@@ -42,3 +44,5 @@ fun RecyclerView(navHostController : NavHostController, orderViewModel: OrderVie
     }
 }
 
+
+

app/src/main/java/com/example/android_programming/dao/SneakerDao.kt

@@ -1,5 +1,6 @@
 package com.example.android_programming.dao
 
+import androidx.paging.PagingSource
 import androidx.room.Dao
 import androidx.room.Delete
 import androidx.room.Insert
@@ -20,7 +21,7 @@ interface SneakerDao {
     suspend fun delete(sneaker: Sneaker)
 
     @Query("SELECT*FROM Sneaker")
-    fun getAllSneakers(): Flow<List<Sneaker>>
+    fun getAllSneakersPaged(): PagingSource<Int, Sneaker>
 
     @Query("SELECT * FROM Sneaker WHERE sneakerId = :id")
     suspend fun getSneakerById(id: Int): Sneaker

app/src/main/java/com/example/android_programming/repository/SneakerRepoImpl.kt

@@ -1,5 +1,10 @@
 package com.example.android_programming.repository
 
+import androidx.paging.Pager
+import androidx.paging.PagingConfig
+import androidx.paging.PagingData
+import androidx.paging.PagingSource
+import androidx.paging.cachedIn
 import com.example.android_programming.dao.SneakerDao
 import com.example.android_programming.model.Sneaker
 import kotlinx.coroutines.flow.Flow
@@ -13,6 +18,12 @@ class SneakerRepoImpl(private val sneakerDao: SneakerDao) : SneakerRepository {
     override suspend fun deleteSneaker(sneaker: Sneaker) = sneakerDao.delete(sneaker)
 
     override suspend fun getSneakerById(id: Int): Sneaker = sneakerDao.getSneakerById(id)
-
+    override fun getAllSneakersPaged(): PagingSource<Int, Sneaker> = sneakerDao.getAllSneakersPaged()
-    override fun getAllSneakers(): Flow<List<Sneaker>> = sneakerDao.getAllSneakers()
+    override fun call(): Flow<PagingData<Sneaker>> {
+        return Pager(
+            PagingConfig(pageSize = 5)
+        ) {
+            sneakerDao.getAllSneakersPaged()
+        }.flow
+    }
 }

app/src/main/java/com/example/android_programming/repository/SneakerRepository.kt

@@ -1,5 +1,7 @@
 package com.example.android_programming.repository
 
+import androidx.paging.PagingData
+import androidx.paging.PagingSource
 import com.example.android_programming.model.Sneaker
 import kotlinx.coroutines.flow.Flow
 
@@ -8,5 +10,6 @@ interface SneakerRepository {
     suspend fun updateSneaker(sneaker: Sneaker)
     suspend fun deleteSneaker(sneaker: Sneaker)
     suspend fun getSneakerById(id: Int): Sneaker
-    fun getAllSneakers(): Flow<List<Sneaker>>
+    fun getAllSneakersPaged(): PagingSource<Int, Sneaker>
+    fun call(): Flow<PagingData<Sneaker>>
 }

app/src/main/java/com/example/android_programming/vmodel/SneakerViewModel.kt

@@ -1,16 +1,24 @@
 package com.example.android_programming.vmodel
 
+import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.ViewModelProvider.AndroidViewModelFactory.Companion.APPLICATION_KEY
 import androidx.lifecycle.viewModelScope
 import androidx.lifecycle.viewmodel.CreationExtras
+import androidx.paging.Pager
+import androidx.paging.PagingConfig
+import androidx.paging.PagingData
+import androidx.paging.cachedIn
+import androidx.paging.map
 import com.example.android_programming.App
 import com.example.android_programming.R
 import com.example.android_programming.database.AppDatabase
 import com.example.android_programming.model.Sneaker
 import com.example.android_programming.repository.SneakerRepository
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.launch
 
 class SneakerViewModel(private val sneakerRepository: SneakerRepository): ViewModel() {
@@ -18,8 +26,8 @@ class SneakerViewModel(private val sneakerRepository: SneakerRepository): ViewMo
     val model = mutableStateOf("")
     val description = mutableStateOf("")
     val price = mutableStateOf("")
-    val photo = mutableStateOf(R.drawable.img)
+    val photo = mutableIntStateOf(R.drawable.img)
-    val SneakerList = sneakerRepository.getAllSneakers()
+    val sneakerList = sneakerRepository.call().cachedIn(viewModelScope)
     var sneaker: Sneaker? = null
 
     fun insertSneaker() = viewModelScope.launch {