How to make a dynamic component in interface layout

i have a problem when i try to develop app calculator, my app is complete successfull run, but the problem is my app just fill a half of screen gadget, i want this app dynamics on all screen size gadget, i want my app fill full the layout screen gadget

this my code of XML

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://ift.tt/nIICcg"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
>

//linear layout textview  
<LinearLayout android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="wrap_content">

<EditText android:layout_width="fill_parent"
android:layout_height = "wrap_content"
android:id="@+id/txtDisplay"
></EditText>

</LinearLayout>
//akhir


//linear layout pertama
<LinearLayout android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1">
<Button android:text="1"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="3"
android:id="@+id/btnSatu"></Button>

<Button android:text="2"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="3"
android:id="@+id/btnDua"></Button>

<Button android:text="3"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="3"
android:id="@+id/btnTiga"></Button>

<Button android:text=":"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="3"
android:id="@+id/btnBagi"></Button>
</LinearLayout>
//akhir

//linear layout ke 2
<LinearLayout android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1">

<Button android:text="4"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnEmpat"></Button>

<Button android:text="5"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnLima"></Button>

<Button android:text="6"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnEnam"></Button>

<Button android:text="x"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnKali"></Button>

</LinearLayout>
//akhir

//linear layout ke 3
<LinearLayout android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1">

<Button android:text="7"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnTujuh"></Button>

<Button android:text="8"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnDelapan"></Button>

<Button android:text="9"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnSembilan"></Button>

<Button android:text="+"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnTambah"></Button>

</LinearLayout>
//akhir

//linear layout ke 4
<LinearLayout android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1">

<Button android:text="0"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnNol"></Button>

<Button android:text="="
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnSamadengan"></Button>

<Button android:text="C"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnReset"></Button>

<Button android:text="-"
android:gravity="center_horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/btnKurang"></Button>

</LinearLayout>
//akhir

</LinearLayout>

Please, your help is my hope, thankyou