Add the layout fragment_authentication_log_in.xml

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

+<?xml version="1.0" encoding="utf-8"?>
+<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <TextView
+        android:id="@+id/text_headline"
+        style="@style/HeadlineTextView"
+        android:text="@string/title_log_in"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintRight_toRightOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <EditText
+        android:id="@+id/text_username"
+        style="@style/AuthenticationEditText"
+        android:layout_marginTop="32dp"
+        android:drawableStart="@drawable/ic_person_black_24dp"
+        android:hint="@string/msg_username"
+        android:imeOptions="actionNext"
+        android:inputType="text"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintRight_toRightOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/text_headline" />
+
+    <EditText
+        android:id="@+id/text_password"
+        style="@style/AuthenticationEditText"
+        android:layout_marginTop="20dp"
+        android:drawableStart="@drawable/ic_lock_black_24dp"
+        android:hint="@string/msg_password"
+        android:imeOptions="actionDone"
+        android:inputType="textPassword"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintRight_toRightOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/text_username" />
+
+    <LinearLayout
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="16dp"
+        android:gravity="center"
+        android:orientation="horizontal"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintRight_toRightOf="parent">
+
+        <TextView
+            android:id="@+id/text_new_in_rocket_chat"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="@string/msg_new_in_rocket_chat" />
+
+        <TextView
+            android:id="@+id/text_sign_up"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="5dp"
+            android:text="@string/title_sign_up"
+            android:textColor="@color/colorAccent" />
+    </LinearLayout>
+
+    <Button
+        android:id="@+id/button_log_in"
+        style="@style/AuthenticationButton"
+        android:text="@string/title_log_in"
+        android:visibility="gone"
+        app:layout_constraintBottom_toBottomOf="parent" />
+
+</android.support.constraint.ConstraintLayout>
\ No newline at end of file