I think it is better to update to current Android configurations. What do you think?

app/build.gradle

@@ -8,13 +8,13 @@ repositories {
 }
 
 android {
-    compileSdkVersion 24
-    buildToolsVersion "24.0.1"
+    compileSdkVersion 27
+    buildToolsVersion '28.0.3'
 
     defaultConfig {
         applicationId "com.google.firebase.udacity.friendlychat"
-        minSdkVersion 16
-        targetSdkVersion 24
+        minSdkVersion 21
+        targetSdkVersion 27
         versionCode 1
         versionName "1.0"
     }
@@ -32,12 +32,12 @@ android {
 }
 
 dependencies {
-    compile fileTree(dir: 'libs', include: ['*.jar'])
-    testCompile 'junit:junit:4.12'
+    implementation fileTree(dir: 'libs', include: ['*.jar'])
+    testImplementation 'junit:junit:4.12'
 
-    compile 'com.android.support:design:24.2.0'
-    compile 'com.android.support:appcompat-v7:24.2.0'
+    implementation 'com.android.support:design:27.1.1'
+    implementation 'com.android.support:appcompat-v7:27.1.1'
 
     // Displaying images
-    compile 'com.github.bumptech.glide:glide:3.6.1'
+    implementation 'com.github.bumptech.glide:glide:4.8.0'
 }

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

@@ -25,22 +25,24 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_alignParentBottom="true"
-        android:layout_alignParentLeft="true"
         android:layout_alignParentStart="true"
         android:orientation="horizontal">
 
         <ImageButton
             android:id="@+id/photoPickerButton"
             android:layout_width="36dp"
             android:layout_height="36dp"
-            android:background="@android:drawable/ic_menu_gallery" />
+            android:background="@android:drawable/ic_menu_gallery"
+            android:contentDescription="@string/image_button"/>
 
         <EditText
             android:id="@+id/messageEditText"
             android:layout_width="0dp"
             android:layout_height="wrap_content"
             android:layout_gravity="center_vertical"
-            android:layout_weight="1" />
+            android:layout_weight="1"
+            android:inputType="text"
+            android:hint="@string/please_write_your_message_here"/>
 
         <Button
             android:id="@+id/sendButton"

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

@@ -3,15 +3,15 @@
               xmlns:tools="http://schemas.android.com/tools"
               android:layout_width="match_parent"
               android:layout_height="wrap_content"
-              android:layout_marginLeft="@dimen/activity_horizontal_margin"
               android:layout_marginStart="@dimen/activity_horizontal_margin"
               android:orientation="vertical">
 
     <ImageView
         android:id="@+id/photoImageView"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:adjustViewBounds="true" />
+        android:adjustViewBounds="true"
+        android:contentDescription="@string/photo_image_view"/>
 
     <TextView
         android:id="@+id/messageTextView"

app/src/main/res/values/strings.xml

@@ -2,4 +2,7 @@
     <string name="app_name">Friendly Chat</string>
     <string name="sign_out">Sign Out</string>
     <string name="send_button_label">Send</string>
+    <string name="please_write_your_message_here">Please Write Your Message Here.</string>
+    <string name="image_button">Image Button</string>
+    <string name="photo_image_view">Photo Image View</string>
 </resources>

build.gradle

@@ -4,9 +4,10 @@ buildscript {
     repositories {
         jcenter()
         mavenLocal()
+        google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.2.2'
+        classpath 'com.android.tools.build:gradle:3.2.1'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
@@ -17,6 +18,7 @@ allprojects {
     repositories {
         jcenter()
         mavenLocal()
+        google()
     }
 }
 

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Tue Aug 16 17:43:49 PDT 2016
+#Fri Oct 19 16:41:19 EET 2018
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-2.14.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.6-all.zip