Android drawable tooltip arrow box

I tried the below code to create a popup window with a tooltip-like arrow on top. picture attached. But I am getting something different as a result.
popup inflater :

LayoutInflater inflater = (LayoutInflater)
                        getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
              View  view = inflater.inflate(R.layout.popup, null);
              mypopupWindow = new PopupWindow(view,500, RelativeLayout.LayoutParams.WRAP_CONTENT, true);            
              mypopupWindow.setBackgroundDrawable(new ColorDrawable(Color.WHITE));
              mypopupWindow.showAsDropDown(v,-153,0);

popup layout :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
<LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="50dp"
        android:layout_marginTop="50dp"
        android:background="@drawable/shadow_recta"
        android:orientation="vertical"
        android:gravity="center">
     <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:text="text long text" />
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Button"/>
</LinearLayout>

drawable file :

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:gravity="top|center_horizontal" >
        <rotate android:fromDegrees="0" android:toDegrees="-45"
            android:pivotX="0%" android:pivotY="50%" >
            <shape android:shape="rectangle">
                <size android:width="24dp" android:height="24dp" />
                <stroke android:color="@android:color/holo_blue_bright" android:width="1dp"/>
            </shape>
        </rotate>
    </item>
    <item>
        <shape android:shape="rectangle">
            <size android:width="206dp" android:height="76dp" />
            <solid android:color="@android:color/white" />
            <stroke android:color="@android:color/holo_blue_bright"  android:width="1dp"/>
            <corners android:radius="2dp" />
        </shape>
    </item>

    <item android:gravity="top|center_horizontal">
        <rotate
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fromDegrees="-45"
            android:pivotX="-50%"
            android:pivotY="60%"
            android:toDegrees="35">
            <shape android:shape="rectangle">
                <solid android:color="@android:color/white" />
                <size
                    android:width="24dp"
                    android:height="24dp" />
                <stroke
                    android:width="1dp"
                    android:color="@android:color/holo_blue_bright" />
            </shape>
        </rotate>
    </item>
</layer-list>

Expected image :

Output i am getting :

Please help me to create a box as in the expected image.

It's not that difficult, key points are three to make this layer-list Drawable:

• The tooltip (triangle) must be fixed size.

• The background must NOT be fixed size, since the content size is unknown.

• Adjust the margin and padding (inside the Drawable).

1. Create the layer-list Drawable:

<layer-list
    xmlns:android="http://schemas.android.com/apk/res/android">

    <item                      //background part
        android:top="17dp">    //margin top, half of the 【rotated】 rectangle height

        <shape
            android:shape="rectangle">

            <solid 
                android:color="@color/purple_200" />

            <corners 
                android:radius="8dp" />

            <padding                    //important part
                android:top="17dp" />   //offset the margin top, shows up the tooltip perfectly

        </shape>

    </item>

    <item                       //tooltip part
        android:width="24dp"    //size must be fixed
        android:height="24dp"
        android:end="32dp"     //margin end (right)
        android:gravity="end"  //place wherever you want 
        android:top="-12dp">   //margin top, negative half of its height, display half of this rotated rectangle

        <rotate 
            android:fromDegrees="45">

            <shape 
                android:shape="rectangle">

                <solid 
                    android:color="@color/purple_500" />    //change back to background part color after your experiment and testing

            </shape>

        </rotate>

    </item>

</layer-list>

2. Apply to View:

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hi, I'm Sam"
    android:textColor="@color/black"
    android:textSize="40sp"
    android:background="@drawable/chat_background"    //here
    android:paddingHorizontal="16dp"/>                //apply padding bottom in Drawable, not in here

<TextView                                             //just for comparison
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="16dp"
    android:text="Hi, I'm Sam"
    android:textColor="@color/black"
    android:textSize="40sp"
    android:background="@color/purple_200"
    android:paddingHorizontal="16dp"/>

Result:

Little Math:

• Un-rotated rectangle height is 24dp.
• Rotated rectangle height is square root of (24^2)*2 = 33.9411.
• Half of the Rotated rectangle height is 16.9706, so we take 17.

Tips For applying vertical padding:

• Modify the padding top of Background part (ex: 17dp + 8dp = 25dp).

• Modify the margin top of Tooltip (rotated rectangle) part to cancel out (ex: -12dp - 8dp = -20dp).