Android中使用系统桌面背景作为应用背景，支持拖动

在Android应用开发中，使用系统桌面背景作为应用的背景，需要把应用的背景设置为透明背景，然后设置窗口的属性为FLAG_SHOW_WALLPAPER即可显示背景。

修改AndroidManifest.xml文件里面activity属性：

        <activity android:name=".WallPaperTest"

                  android:label="@string/app_name"

                  android:theme="@android:style/Theme.Translucent">

然后在使用的时候，在onCreate里面添加一个窗口属性

getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WALLPAPER);

在背景拖动的时候主要是使用了WallpaperManager这个类的两个方法

public void setWallpaperOffsetSteps (float xStep, float yStep)

Since: API Level 7

For applications that use multiple virtual screens showing a wallpaper, specify the step size between virtual screens. For example, if the launcher has 3 virtual screens, it would specify an xStep of 0.5, since the X offset for those screens are 0.0, 0.5 and 1.0

Parameters

xStep	The X offset delta from one screen to the next one
yStep	The Y offset delta from one screen to the next one

public void setWallpaperOffsets (IBinder windowToken, float xOffset, float yOffset)

Since: API Level 5

Set the position of the current wallpaper within any larger space, when that wallpaper is visible behind the given window. The X and Y offsets are floating point numbers ranging from 0 to 1, representing where the wallpaper should be positioned within the screen space. These only make sense when the wallpaper is larger than the screen.

Parameters

windowToken	The window who these offsets should be associated with, as returned by View.getWindowToken().
xOffset	The offset along the X dimension, from 0 to 1.
yOffset	The offset along the Y dimension, from 0 to 1. http://blog.csdn.net/yao_guet/article/details/6572739