布局问题新手

<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=".MainActivity" >
    <TextView
        android:name="@+id/label"
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
       android:text="@string/mobile" />
<EditText 
    android:name="@+id/text"
    android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:inputType="phone"
        android:layout_below="@id/label"
    />
<Button
    android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/text"
        android:text="@string/button" />
    
</RelativeLayout>
为什么三个控件还是重叠到一起了啊Android布局控件