diff --git a/apng_sample/build.gradle b/apng_sample/build.gradle
index d6e72565..7c52b339 100644
--- a/apng_sample/build.gradle
+++ b/apng_sample/build.gradle
@@ -37,7 +37,7 @@ dependencies {
 
     implementation project(':apng_android')
 
-    implementation 'com.android.support:appcompat-v7:27.0.2'
+    implementation 'com.android.support:appcompat-v7:27.1.0'
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'com.android.support.test:runner:1.0.1'
     androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
diff --git a/app/build.gradle b/app/build.gradle
index a84be9c7..6133e919 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -69,11 +69,11 @@ dependencies {
     implementation project(':emoji')
     implementation project(':apng_android')
 
-    compile 'com.android.support:support-v4:27.0.2'
-    compile 'com.android.support:appcompat-v7:27.0.2'
-    compile 'com.android.support:design:27.0.2'
-    compile 'com.android.support:customtabs:27.0.2'
-    compile 'com.android.support:support-v13:27.0.2'
+    compile 'com.android.support:support-v4:27.1.0'
+    compile 'com.android.support:appcompat-v7:27.1.0'
+    compile 'com.android.support:design:27.1.0'
+    compile 'com.android.support:customtabs:27.1.0'
+    compile 'com.android.support:support-v13:27.1.0'
 
     compile 'com.google.firebase:firebase-core:11.8.0'
     compile 'com.google.firebase:firebase-messaging:11.8.0'
diff --git a/app/src/main/java/jp/juggler/subwaytooter/ItemListAdapter.kt b/app/src/main/java/jp/juggler/subwaytooter/ItemListAdapter.kt
index ed4402a3..72d171d4 100644
--- a/app/src/main/java/jp/juggler/subwaytooter/ItemListAdapter.kt
+++ b/app/src/main/java/jp/juggler/subwaytooter/ItemListAdapter.kt
@@ -81,7 +81,7 @@ internal class ItemListAdapter(
 		return headerType.viewType
 	}
 	
-	override fun onCreateViewHolder(parent : ViewGroup?, viewType : Int) : RecyclerView.ViewHolder {
+	override fun onCreateViewHolder(parent : ViewGroup, viewType : Int) : RecyclerView.ViewHolder {
 		when(viewType) {
 			0 -> {
 				val holder = ItemViewHolder(activity)
diff --git a/app/src/main/java/jp/juggler/subwaytooter/ItemViewHolder.kt b/app/src/main/java/jp/juggler/subwaytooter/ItemViewHolder.kt
index d768b1e8..1c56aa4f 100644
--- a/app/src/main/java/jp/juggler/subwaytooter/ItemViewHolder.kt
+++ b/app/src/main/java/jp/juggler/subwaytooter/ItemViewHolder.kt
@@ -1453,9 +1453,10 @@ internal class ItemViewHolder(
 									
 									ivMedia1 = myNetworkImageView {
 										
+										
 										background = ContextCompat.getDrawable(
 											context,
-											R.drawable.btn_bg_ddd
+											R.drawable.bg_thumbnail
 										)
 										contentDescription = context.getString(R.string.thumbnail)
 										scaleType = ImageView.ScaleType.CENTER_CROP
@@ -1468,7 +1469,7 @@ internal class ItemViewHolder(
 										
 										background = ContextCompat.getDrawable(
 											context,
-											R.drawable.btn_bg_ddd
+											R.drawable.bg_thumbnail
 										)
 										contentDescription = context.getString(R.string.thumbnail)
 										scaleType = ImageView.ScaleType.CENTER_CROP
@@ -1482,7 +1483,7 @@ internal class ItemViewHolder(
 										
 										background = ContextCompat.getDrawable(
 											context,
-											R.drawable.btn_bg_ddd
+											R.drawable.bg_thumbnail
 										)
 										contentDescription = context.getString(R.string.thumbnail)
 										scaleType = ImageView.ScaleType.CENTER_CROP
@@ -1496,7 +1497,7 @@ internal class ItemViewHolder(
 										
 										background = ContextCompat.getDrawable(
 											context,
-											R.drawable.btn_bg_ddd
+											R.drawable.bg_thumbnail
 										)
 										contentDescription = context.getString(R.string.thumbnail)
 										scaleType = ImageView.ScaleType.CENTER_CROP
diff --git a/app/src/main/res/drawable/bg_thumbnail.xml b/app/src/main/res/drawable/bg_thumbnail.xml
new file mode 100644
index 00000000..ac59f2d3
--- /dev/null
+++ b/app/src/main/res/drawable/bg_thumbnail.xml
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ripple
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:color="?attr/colorRippleEffect"
+    >
+    <item android:drawable="?attr/colorThumbnailBackground"/>
+</ripple>
diff --git a/app/src/main/res/values/attrs.xml b/app/src/main/res/values/attrs.xml
index 5fe4df6b..30cebff1 100644
--- a/app/src/main/res/values/attrs.xml
+++ b/app/src/main/res/values/attrs.xml
@@ -70,6 +70,9 @@
     <!-- カラムストリップの背景色 -->
     <attr name="colorColumnStripBackground" format="color"/>
 
+    <!-- サムネイルの背景色 -->
+    <attr name="colorThumbnailBackground" format="color"/>
+
     <attr name="btn_attachment" format="reference" />
     <attr name="btn_boost" format="reference" />
     <attr name="btn_close" format="reference" />
diff --git a/app/src/main/res/values/colors.xml b/app/src/main/res/values/colors.xml
index d1da0141..a6a5b14e 100644
--- a/app/src/main/res/values/colors.xml
+++ b/app/src/main/res/values/colors.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
+    <color name="Light_colorThumbnailBackground">#20000000</color>
     <color name="Light_colorColumnListItemText">#80000000</color>
     <color name="Light_colorTimeSmall">#80000000</color>
     <color name="Light_colorColumnHeaderAcct">#80000000</color>
@@ -30,7 +31,6 @@
 
     <color name="Light_colorBackground">#fff</color>
     <color name="Light_colorColumnStripBackground">#fff</color>
-
     <color name="Light_colorPrimaryDark">#303030</color> <!-- ステータスバー背景 -->
 
     <!-- 以下は白テーマでも黒テーマでもだいたい同じ -->
@@ -46,6 +46,7 @@
 
     <!-- Dark theme -->
 
+    <color name="Dark_colorThumbnailBackground">#20ffffff</color>
     <color name="Dark_colorColumnListItemText">#66FFFFFF</color>
     <color name="Dark_colorTimeSmall">#66FFFFFF</color>
     <color name="Dark_colorColumnHeaderAcct">#66FFFFFF</color>
diff --git a/app/src/main/res/values/styles.xml b/app/src/main/res/values/styles.xml
index 5566a7b6..0feea2b6 100644
--- a/app/src/main/res/values/styles.xml
+++ b/app/src/main/res/values/styles.xml
@@ -26,6 +26,7 @@
         <item name="colorColumnListDragHandleBackground">
             @color/Light_colorColumnListDragHandleBackground
         </item>
+        <item name="colorThumbnailBackground">@color/Light_colorThumbnailBackground</item>
         <item name="colorColumnListItemText">@color/Light_colorColumnListItemText</item>
         <item name="colorTimeSmall">@color/Light_colorTimeSmall</item>
         <item name="colorProfileBackgroundMask">@color/Light_colorProfileBackgroundMask</item>
@@ -140,6 +141,8 @@
         <item name="colorColumnListDragHandleBackground">
             @color/Dark_colorColumnListDragHandleBackground
         </item>
+        <item name="colorThumbnailBackground">@color/Dark_colorThumbnailBackground</item>
+
         <item name="colorColumnListItemText">@color/Dark_colorColumnListItemText</item>
         <item name="colorTimeSmall">@color/Dark_colorTimeSmall</item>
         <item name="colorProfileBackgroundMask">@color/Dark_colorProfileBackgroundMask</item>
@@ -219,6 +222,7 @@
         <item name="ic_right">@drawable/ic_right_dark</item>
         <item name="ic_volume_up">@drawable/ic_volume_up_dark</item>
         <item name="ic_face">@drawable/ic_face_dark</item>
+
     </style>
 
     <style name="AppTheme.Dark.NoActionBar" parent="AppTheme.Dark">
diff --git a/build.gradle b/build.gradle
index ea4233a2..8d48c357 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,6 +1,6 @@
 buildscript {
 
-    ext.kotlin_version = '1.2.21'
+    ext.kotlin_version = '1.2.30'
     ext.kotlin_coroutines_version = '0.21.2'
     ext.anko_version='0.10.4'
 
diff --git a/colorpicker/build.gradle b/colorpicker/build.gradle
index 69177375..ac8b2ebe 100644
--- a/colorpicker/build.gradle
+++ b/colorpicker/build.gradle
@@ -16,7 +16,7 @@ android {
 }
 
 dependencies {
-  compile 'com.android.support:appcompat-v7:27.0.2'
+  compile 'com.android.support:appcompat-v7:27.1.0'
 }
 
 //apply plugin: 'com.getkeepsafe.dexcount'
diff --git a/emoji/build.gradle b/emoji/build.gradle
index b85da2cd..6e88fa0a 100644
--- a/emoji/build.gradle
+++ b/emoji/build.gradle
@@ -27,7 +27,7 @@ android {
 dependencies {
     implementation fileTree(dir: 'libs', include: ['*.jar'])
 
-    implementation 'com.android.support:appcompat-v7:27.0.2'
+    implementation 'com.android.support:appcompat-v7:27.1.0'
 //    testImplementation 'junit:junit:4.12'
 //    androidTestImplementation 'com.android.support.test:runner:1.0.1'
 //    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'