爲什麼Android Softkeyboard隱藏最底層的TextView？

這是我的Fragment的佈局文件。爲什麼Android Softkeyboard隱藏最底層的TextView？

<?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="match_parent" > 

    <!-- android:fillViewport="true" --> 

    <EditText 
     android:id="@+id/chatDispWindow" 
     android:layout_width="fill_parent" 
     android:layout_height="match_parent" 
     android:layout_above="@+id/chatTypeWindow" 
     android:layout_alignParentTop="true" 
     android:layout_marginLeft="9dp" 
     android:layout_marginRight="6dp" 
     android:background="@color/background_color" 
     android:clickable="false" 
     android:cursorVisible="false" 
     android:focusable="false" 
     android:focusableInTouchMode="false" 
     android:gravity="bottom" 
     android:inputType="textMultiLine|textLongMessage|textNoSuggestions" 
     android:scrollHorizontally="true" /> 
    <!-- android:hint="@string/groupChatDispMsg" --> 

    <ImageButton 
     android:id="@+id/sendBtn" 
     android:layout_width="52dp" 
     android:layout_height="46dp" 
     android:layout_above="@+id/chatStatusWindow" 
     android:layout_alignBottom="@+id/chatTypeWindow" 
     android:layout_alignParentRight="true" 
     android:layout_marginBottom="-3dp" 
     android:layout_marginLeft="4dp" 
     android:background="@drawable/send_chatbtn_selector" 
     android:contentDescription="@string/sendLbl" /> 

    <EditText 
     android:id="@+id/chatTypeWindow" 
     android:layout_width="match_parent" 
     android:layout_height="45dp" 
     android:layout_above="@+id/chatStatusWindow" 
     android:layout_alignParentLeft="true" 
     android:layout_marginLeft="6dp" 
     android:layout_toLeftOf="@+id/sendBtn" 
     android:background="@drawable/editbox_selector" 
     android:imeActionId="@+id/sendChatImeBtn" 
     android:imeActionLabel="@string/sendLbl" 
     android:imeOptions="actionSend" 
     android:inputType="textMultiLine" 
     android:minHeight="45dp" /> 
    <!-- android:hint="@string/chatWindowMsg" --> 

    <TextView 
     android:id="@+id/chatStatusWindow" 
     android:layout_width="match_parent" 
     android:layout_height="15dp" 
     android:layout_alignParentBottom="true" 
     android:layout_marginBottom="3dp" 
     android:layout_marginLeft="9dp" /> 
    <!-- android:text="@string/chatStatusMsg" --> 

</RelativeLayout>

這是現在應用的行爲......

Default View Ui When User clicks on the EditText