activity_task.xml

<android.support.design.widget.CoordinatorLayout
    android:id="@+id/main_content"
    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">

    <ListView

        android:id="@+id/taskList"
        android:layout_width="match_parent"
        android:layout_height="match_parent"></ListView>


    <android.support.design.widget.FloatingActionButton
        android:id="@+id/myFab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:layout_margin="16dp"
        android:src="@mipmap/add1"
        app:layout_anchor="@id/taskList"
        app:layout_anchorGravity="bottom|right" />


</android.support.design.widget.CoordinatorLayout>