update

app/build.gradle

@@ -1,4 +1,5 @@
 apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
 
 android {
     compileSdkVersion 26
@@ -30,5 +31,9 @@ dependencies {
     androidTestImplementation('com.android.support.test.espresso:espresso-core:3.0.1', {
         exclude group: 'com.android.support', module: 'support-annotations'
     })
+    compile "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
 
 }
+repositories {
+    mavenCentral()
+}

app/src/main/java/cloud/techstar/imageloader/FileCache.kt

@@ -0,0 +1,38 @@
+package cloud.techstar.imageloader
+
+import android.content.Context
+
+import java.io.File
+
+/**
+ * @author Turtuvshin Byambaa
+ * Copyright (C) 2018 Techstar, Inc.
+ * www.techstar.cloud
+ */
+
+class FileCache(context: Context) {
+
+    private var cacheDir: File? = null
+
+    init {
+
+        if (android.os.Environment.getExternalStorageState() == android.os.Environment.MEDIA_MOUNTED)
+            cacheDir = File(android.os.Environment.getExternalStorageDirectory(), "dir")
+        else
+            cacheDir = context.cacheDir
+        if (!cacheDir!!.exists())
+            cacheDir!!.mkdirs()
+    }
+
+    fun getFile(url: String): File {
+        val filename = url.hashCode().toString()
+        return File(cacheDir, filename)
+
+    }
+
+    fun clear() {
+        val files = cacheDir!!.listFiles() ?: return
+        for (f in files)
+            f.delete()
+    }
+}