为什么我在eclipse中看不到图形化android-layout预览？

Question

我有这个xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/settingsSwitchMainLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:clickable="true" >

    <ImageView
        android:id="@+id/switch_bg"
        android:layout_width="50dp"
        android:layout_height="40dp"
        android:layout_alignParentRight="true"
        android:layout_centerInParent="true"
        android:layout_centerVertical="true"
        android:layout_marginRight="7dp"
        android:src="@drawable/switch_bg_on" />

    <RelativeLayout
        android:id="@+id/switch_handle"
        android:layout_width="38dp"
        android:layout_height="38dp"
        android:layout_alignParentRight="true"
        android:layout_marginRight="4dp"
        android:layout_marginTop="6dp"
        android:background="@drawable/switch_handle"
        android:padding="0dp" >

        <ImageView
            android:id="@+id/switch_v"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="12dp"
            android:layout_marginTop="9dp"
            android:src="@drawable/switch_v"
            android:visibility="visible" />
    </RelativeLayout>

     <com.me.view.text.MyTextView
        android:id="@+id/switch_text"
        style="@style/settingsText"
        android:layout_centerVertical="true"
        android:layout_toLeftOf="@id/switch_bg"
        android:layout_alignParentLeft="true"
        android:layout_marginLeft="10dp"
        android:gravity="center_vertical"
        android:text="Text long Text long Text long Text long Text long Text long " />


</RelativeLayout>

当我切换到graphical preview时，看不到预览并且

我第一次遇到这个错误：

The project target is not set. Right click project, choose Properties | Android.

然后我将目标视图更改为Android 4.2.1

并得到了这个新错误

No resources match the configuration

    default

Change the configuration or create:

    res/layout/settings_switch.xml

You can also click the 'Create New...' item in the configuration dropdown menu above.