ImageViewer: Use Ktor and expect/actual to make common source set pure Kotlin (#51)

* Add IDE resolution warning for examples sharing JVM & Android code.

* Use Ktor to remove JVM-specific networking code from common source set
Fix resolution for Picture class via expect/actual mechanism

Co-authored-by: Sebastian Aigner <sebastian.aigner@jetbrains.com>

examples/imageviewer/common/build.gradle.kts

@@ -9,24 +9,26 @@ plugins {
 kotlin {
     android()
     jvm("desktop")
-
     sourceSets {
         named("commonMain") {
             dependencies {
                 api(compose.runtime)
                 api(compose.foundation)
                 api(compose.material)
+                implementation("io.ktor:ktor-client-core:1.4.1")
             }
         }
         named("androidMain") {
             dependencies {
                 api("androidx.appcompat:appcompat:1.1.0")
                 api("androidx.core:core-ktx:1.3.1")
+                implementation("io.ktor:ktor-client-cio:1.4.1")
             }
         }
         named("desktopMain") {
             dependencies {
                 api(compose.desktop.common)
+                implementation("io.ktor:ktor-client-cio:1.4.1")
             }
         }
     }

examples/imageviewer/common/src/androidMain/kotlin/example/imageviewer/model/Picture.kt

@@ -2,7 +2,7 @@ package example.imageviewer.model
 
 import android.graphics.Bitmap
 
-data class Picture(
+actual data class Picture(
     var source: String = "",
     var name: String = "",
     var image: Bitmap,

examples/imageviewer/common/src/androidMain/kotlin/example/imageviewer/utils/Coroutines.kt

@@ -0,0 +1,9 @@
+package example.imageviewer.utils
+
+import kotlinx.coroutines.CoroutineScope
+import kotlin.coroutines.CoroutineContext
+
+actual fun <T> runBlocking(
+    context: CoroutineContext,
+    block: suspend CoroutineScope.() -> T
+): T = kotlinx.coroutines.runBlocking(context, block)

examples/imageviewer/common/src/commonMain/kotlin/example/imageviewer/model/ImageRepository.kt

@@ -16,36 +16,18 @@
 package example.imageviewer.model
 
 import example.imageviewer.core.Repository
-import java.io.BufferedReader
+import example.imageviewer.utils.ktorHttpClient
-import java.io.InputStreamReader
+import example.imageviewer.utils.runBlocking
-import java.net.HttpURLConnection
+import io.ktor.client.request.*
-import java.net.URL
 
 class ImageRepository(
     private val httpsURL: String
 ) : Repository<MutableList<String>> {
 
     override fun get(): MutableList<String> {
-        val list: MutableList<String> = ArrayList()
+        return runBlocking {
-        try {
+            val content = ktorHttpClient.get<String>(httpsURL)
-            val url = URL(httpsURL)
+            content.lines().toMutableList()
-            val connection: HttpURLConnection = url.openConnection() as HttpURLConnection
-            connection.connectTimeout = 5000
-            connection.connect()
-
-            val read = BufferedReader(InputStreamReader(connection.inputStream))
-
-            var line: String? = read.readLine()
-            while (line != null) {
-                list.add(line)
-                line = read.readLine()
-            }
-            read.close()
-            return list
-        } catch (e: Exception) {
-            e.printStackTrace()
         }
-
-        return list
     }
 }

examples/imageviewer/common/src/commonMain/kotlin/example/imageviewer/model/Miniatures.kt

@@ -14,20 +14,21 @@
 
 package example.imageviewer.model
 
+expect class Picture
 
 class Miniatures(
-    private var list: MutableList<Picture> = ArrayList()
+    private var list: List<Picture> = emptyList()
 ) {
     fun get(index: Int): Picture {
         return list[index]
     }
 
     fun getMiniatures(): List<Picture> {
-        return ArrayList(list)
+        return list.toList()
     }
 
     fun setMiniatures(list: List<Picture>) {
-        this.list = ArrayList(list)
+        this.list = list.toList()
     }
 
     fun size(): Int {
@@ -35,6 +36,6 @@ class Miniatures(
     }
 
     fun clear() {
-        list = ArrayList()
+        list = emptyList()
     }
 }

examples/imageviewer/common/src/commonMain/kotlin/example/imageviewer/utils/Coroutines.kt

@@ -0,0 +1,7 @@
+package example.imageviewer.utils
+
+import kotlinx.coroutines.CoroutineScope
+import kotlin.coroutines.CoroutineContext
+import kotlin.coroutines.EmptyCoroutineContext
+
+expect fun <T> runBlocking(context: CoroutineContext = EmptyCoroutineContext, block: suspend CoroutineScope.() -> T): T

examples/imageviewer/common/src/commonMain/kotlin/example/imageviewer/utils/Network.kt

@@ -14,13 +14,24 @@
 
 package example.imageviewer.utils
 
-import java.net.InetAddress
+import io.ktor.client.*
+import io.ktor.client.request.*
+import kotlinx.coroutines.Deferred
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.async
+
+//import java.net.InetAddress
 
 fun isInternetAvailable(): Boolean {
-    return try {
+    return runBlocking {
-        val ipAddress: InetAddress = InetAddress.getByName("google.com")
+        try {
-        !ipAddress.equals("")
+            ktorHttpClient.head<String>("http://google.com")
-    } catch (e: Exception) {
+            true
-        false
+        } catch (e: Exception) {
+            println(e.message)
+            false
+        }
     }
-}
+}
+
+val ktorHttpClient = HttpClient {}

examples/imageviewer/common/src/desktopMain/kotlin/example/imageviewer/model/Picture.kt

@@ -2,7 +2,7 @@ package example.imageviewer.model
 
 import java.awt.image.BufferedImage
 
-data class Picture(
+actual data class Picture(
     var source: String = "",
     var name: String = "",
     var image: BufferedImage,

examples/imageviewer/common/src/desktopMain/kotlin/example/imageviewer/utils/Coroutines.kt

@@ -0,0 +1,9 @@
+package example.imageviewer.utils
+
+import kotlinx.coroutines.CoroutineScope
+import kotlin.coroutines.CoroutineContext
+
+actual fun <T> runBlocking(
+    context: CoroutineContext,
+    block: suspend CoroutineScope.() -> T
+): T = kotlinx.coroutines.runBlocking(context, block)