Half circle shape not work

curve_toolbar_bg.xml

<?xml version="1.0" encoding="utf-8"?><layer-list xmlns:android="http://schemas.android.com/apk/res/android">    <item>        <shape android:shape="rectangle"/>    </item>    <item        android:bottom="0dp"        android:left="-100dp"        android:right="-100dp"        android:top="-80dp">        <shape android:shape="oval">            <solid android:color="@color/colorPrimary" />        </shape>    </item></layer-list>

activity_main.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"    xmlns:tools="http://schemas.android.com/tools"    android:id="@+id/container"    android:layout_width="match_parent"    android:layout_height="match_parent">    <android.support.v7.widget.Toolbar        android:id="@+id/toolbar"        android:layout_width="0dp"        android:layout_height="?android:attr/actionBarSize"        android:background="@drawable/rounded_corner"        app:layout_constraintBottom_toBottomOf="parent"        app:layout_constraintEnd_toEndOf="parent"        app:layout_constraintStart_toStartOf="parent"        app:layout_constraintTop_toTopOf="parent"        app:layout_constraintVertical_bias="0.0">    </android.support.v7.widget.Toolbar></android.support.constraint.ConstraintLayout>

you can try this :

<?xml version="1.0" encoding="utf-8"?><shape    xmlns:android="http://schemas.android.com/apk/res/android"    android:shape="rectangle">    <solid android:color="#900021df"/>    <size        android:width="10dp"        android:height="5dp"/>    <corners        android:bottomLeftRadius="20dp"        android:bottomRightRadius="20dp"/></shape>

it gives this shape:

You cannot create a semicircle from xml. but you could achieve what you are looking for using a circle with appropriate margin & padding.

You can use a circle shape .xml file.Create a fixed sized circle like this:

Example:

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"       android:shape="oval"       android:useLevel="false" >   <solid android:color="#006AC5" />   <size    android:height="50dp"    android:width="50dp" /></shape>