Countdown Timer displaying remaining day, hours, minutes and seconds

In this blog, i am trying to display count down timer.

1. Xml code to display count down timer (main.xml)
    Take 4 textviews to display days, hours, minutes and seconds.
    And a button to start the timer.

 <Button

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:text="Start Countdown"

    android:onClick="startCountDown"/>

 <LinearLayout

    android:layout_width="match_parent"

    android:layout_height="wrap_content"

    android:orientation="horizontal"

    android:layout_marginTop="100dp">

    <LinearLayout

        android:layout_width="0dp"

        android:layout_height="match_parent"

        android:layout_weight="0.25">

        <TextView

            android:id="@+id/days"

            android:layout_width="match_parent"

            android:layout_height="match_parent"

            android:text="Days"

            android:gravity="center"/>

    </LinearLayout>

    <LinearLayout

        android:layout_width="0dp"

        android:layout_height="match_parent"

        android:layout_weight="0.25">

        <TextView

            android:id="@+id/hours"

            android:layout_width="match_parent"

            android:layout_height="match_parent"

            android:text="Hours"

            android:gravity="center"/>

    </LinearLayout>

    <LinearLayout

        android:layout_width="0dp"

        android:layout_height="match_parent"

        android:layout_weight="0.25">

        <TextView

            android:id="@+id/minutes"

            android:layout_width="match_parent"

            android:layout_height="match_parent"

            android:text="Minutes"

            android:gravity="center"/>

    </LinearLayout>

    <LinearLayout

        android:layout_width="0dp"

        android:layout_height="match_parent"

        android:layout_weight="0.25">

        <TextView

            android:id="@+id/seconds"

            android:layout_width="match_parent"

            android:layout_height="match_parent"

            android:text="Seconds"

            android:gravity="center"/>

    </LinearLayout>

</LinearLayout>