android中控件的遮蓋問題

如下：會造成imagebutton被遮蓋

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#ffffff"
    >
    <ImageButton
     android:id="@+id/proper_scan_result_refresh"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/refresh"
        android:layout_marginTop="3dip"
        android:layout_marginRight="5dip"
        android:layout_alignParentRight="true"
    />
    <TextView
    android:id="@+id/proper_scan_result_title"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="請您選擇要連接的網絡"
        style="?android:attr/textAppearanceLarge"
        android:textColor="#3a3a3a"
        android:paddingLeft="10dip"
        android:gravity="left|center_vertical"
        android:background="@drawable/system_title_bg"
    />

</RelativeLayout>

 

 

但如果這樣寫，則imagebutton會浮在textview之上

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#ffffff"
    >
    <TextView
    android:id="@+id/proper_scan_result_title"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="請您選擇要連接的網絡"
        style="?android:attr/textAppearanceLarge"
        android:textColor="#3a3a3a"
        android:paddingLeft="10dip"
        android:gravity="left|center_vertical"
        android:background="@drawable/system_title_bg"
    />
    <ImageButton
     android:id="@+id/proper_scan_result_refresh"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/refresh"
        android:layout_marginTop="3dip"
        android:layout_marginRight="5dip"
        android:layout_alignParentRight="true"
    />

</RelativeLayout>