hint not working

[Akash Agrawal]

Hint is not working in my edit text
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="25dp"

            android:orientation="vertical">

            <com.github.florent37.materialtextfield.MaterialTextField
                android:layout_width="300dp"
                android:layout_height="wrap_content"

                app:mtf_image="@drawable/man">

                <EditText
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:hint="@string/rollno"
                    android:textColor="#333"
                    android:textColorHint="#666"
                    android:textSize="15sp"
                    android:ellipsize="end"


                     />

            </com.github.florent37.materialtextfield.MaterialTextField>

            <com.github.florent37.materialtextfield.MaterialTextField
                android:layout_width="300dp"
                android:layout_height="wrap_content"

                app:mtf_image="@drawable/man">

                <EditText
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:hint="@string/rollno"

                    android:textColor="#333"
                    android:textColorHint="#666"
                    android:textSize="15sp"
                    android:ellipsize="end"

                     />

            </com.github.florent37.materialtextfield.MaterialTextField>
        </LinearLayout>