Android Launcher View构架浅析

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

<com.Android.Launcher.DragLayer

    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">

    <!-- The workspace contains 3 screens of cells -->

    <com.android.Launcher.Workspace

        android:id="@+id/workspace"

        android:layout_width="fill_parent"

        android:layout_height="fill_parent"

        launcher:defaultScreen="1">

        <include android:id="@+id/cell1" layout="@layout/workspace_screen" />

        <include android:id="@+id/cell2" layout="@layout/workspace_screen" />

        <include android:id="@+id/cell3" layout="@layout/workspace_screen" />

    </com.android.Launcher.Workspace>

    <SlidingDrawer

        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">

        <com.android.Launcher.HandleView

            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" />

        <com.android.Launcher.AllAppsGridView

            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" />

    </SlidingDrawer>

    <com.android.Launcher.DeleteZone

        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" />

</com.android.Launcher.DragLayer>

3. 呈现界面：()

其中Workspace可增加到任意多个cell，如7个：

        launcher:defaultScreen="3">

        <include android:id="@+id/cell1" layout="@layout/workspace_screen" />

        <include android:id="@+id/cell2" layout="@layout/workspace_screen" />

        <include android:id="@+id/cell3" layout="@layout/workspace_screen" />

        <include android:id="@+id/cell4" layout="@layout/workspace_screen" />

        <include android:id="@+id/cell5" layout="@layout/workspace_screen" />

        <include android:id="@+id/cell6" layout="@layout/workspace_screen" />

        <include android:id="@+id/cell7" layout="@layout/workspace_screen" />