1. 先来看一下launcher activity view的架构图（hierarchyviewer.bat工具获取）：
2. 再来看layout/launcher.xml, layout-port/launcher.xml, layout-land/launcher.xml
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:launcher="http://schemas.android.com/apk/res/com.android.Launcher"
android:id="@+id/drag_layer"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#FFF">
android:id="@+id/workspace"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
launcher:defaultScreen="1">
android:id="@+id/drawer"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal"
android:bottomOffset="4dip"
android:handle="@+id/all_apps"
android:content="@+id/content">
android:id="@id/all_apps"
android:layout_width="56dip"
android:layout_height="56dip"
android:background="@drawable/handle"
android:focusable="true"
android:clickable="true"
android:scaleType="center"
android:src="@drawable/handle_icon"
launcher:direction="vertical" />
android:id="@id/content"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
launcher:texture="@drawable/pattern_carbon_fiber_dark"
android:scrollbarStyle="outsideInset"
android:drawSelectorOnTop="false"
android:listSelector="@drawable/grid_selector"
android:nextFocusLeft="@id/all_apps"
android:nextFocusDown="@id/content"
android:nextFocusUp="@id/content"
android:nextFocusRight="@id/content"
android:verticalSpacing="10dip"
android:numColumns="5" />
android:id="@+id/delete_zone"
android:layout_width="49dip"
android:layout_height="wrap_content"
android:scaleType="center"
android:src="@drawable/ic_delete"
android:background="@drawable/delete_zone_selector"
android:layout_marginBottom="-25dip"
android:layout_gravity="right|center_vertical"
android:visibility="gone"
launcher:direction="vertical" />
3. 呈现界面：()
其中Workspace可增加到任意多个cell，如7个：
launcher:defaultScreen="3">