Make editText to fullscreen

Question

I want to make editText become fullscreen when I want to type something on it.

something like this:

at first I was able to do this without doing anything, but then I tried to use external keyboard - because using soft keyboard block some of my editText - and it wont come out like this again.

I tried make my editText bigger and use scrollView, but my app have a capture signature using Canvas and it wont work if I put scrollView on it.

My XML code:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".myActivity" >

    <EditText
        android:id="@+id/edtText1"
        android:layout_width="300dip"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_weight="1"
        android:ems="10"
        android:gravity="top"
        android:inputType="textShortMessage|textAutoCorrect|textCapSentences|textMultiLine"
        android:windowSoftInputMode="stateVisible|adjustResize"
        android:imeOptions="actionSend|flagNoEnterAction"
        android:maxLines="1" />

    <LinearLayout
        android:id="@+id/linearLayout1"
        android:layout_width="350dp"
        android:layout_height="150dp">
    </LinearLayout>

</RelativeLayout>

I'm not putting everything here, only the one I think I need to show you.

I want to make edtText1 to become like as an example that I have given above.

And linearLayout1 is canvas for capture signature, if I put scrollview, my linearLayout1 won't work. (scrollview is working)