Android中使用系统桌面背景作为应用背景，支持拖动

public void setWallpaperOffsetSteps (float xStep, float yStep)

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

View.getWindowToken()

package com.yao_guet;
import android.app.WallpaperManager;
import android.content.Context;
import android.os.IBinder;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;
/**
* 仿Launcher中的WorkSapce，可以左右滑动切换屏幕的类，支持显示系统背景和滑动
* @author Yao.GUET
* blog: http://blog.csdn.net/Yao_GUET * date: 2011-05-04
*/
public class ScrollLayout extends ViewGroup {
private static final String TAG = "ScrollLayout";
private Scroller mScroller;
private VelocityTracker mVelocityTracker;

private int mCurScreen;
private int mDefaultScreen = 0;

private static final int TOUCH_STATE_REST = 0;
private static final int TOUCH_STATE_SCROLLING = 1;

private static final int SNAP_VELOCITY = 600;

private int mTouchState = TOUCH_STATE_REST;
private int mTouchSlop;
private float mLastMotionX;
private float mLastMotionY;

private WallpaperManager mWallpaperManager;
private int mScrollX;
public ScrollLayout(Context context, AttributeSet attrs) {
this(context, attrs, 0);
// TODO Auto-generated constructor stub
}
public ScrollLayout(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub

mWallpaperManager = WallpaperManager.getInstance(context);
mScroller = new Scroller(context);

mCurScreen = mDefaultScreen;
mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
// TODO Auto-generated method stub
Log.e(TAG, "onLayout");
int childLeft = 0;
final int childCount = getChildCount();

for (int i=0; i<childCount; i++) {
final View childView = getChildAt(i);
if (childView.getVisibility() != View.GONE) {
final int childWidth = childView.getMeasuredWidth();
childView.layout(childLeft, 0,
childLeft+childWidth, childView.getMeasuredHeight());
childLeft += childWidth;
}
}
updateWallpaperOffset();
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
Log.e(TAG, "onMeasure");
super.onMeasure(widthMeasureSpec, heightMeasureSpec);

final int width = MeasureSpec.getSize(widthMeasureSpec);
final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
if (widthMode != MeasureSpec.EXACTLY) {
throw new IllegalStateException("ScrollLayout only canmCurScreen run at EXACTLY mode!");
}

final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
if (heightMode != MeasureSpec.EXACTLY) {
throw new IllegalStateException("ScrollLayout only can run at EXACTLY mode!");
}

// The children are given the same width and height as the scrollLayout
final int count = getChildCount();
for (int i = 0; i < count; i++) {
getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
}
// Log.e(TAG, "moving to screen "+mCurScreen);
scrollTo(mCurScreen * width, 0);
}

/**
* According to the position of current layout
* scroll to the destination page.
*/
public void snapToDestination() {
final int screenWidth = getWidth();
final int destScreen = (getScrollX()+ screenWidth/2)/screenWidth;
snapToScreen(destScreen);
}

public void snapToScreen(int whichScreen) {
// get the valid layout page
whichScreen = Math.max(0, Math.min(whichScreen, getChildCount()-1));
if (getScrollX() != (whichScreen*getWidth())) {

final int delta = whichScreen*getWidth()-getScrollX();
mScroller.startScroll(getScrollX(), 0,
delta, 0, Math.abs(delta)*2);
mCurScreen = whichScreen;
invalidate();		// Redraw the layout
}
}

public void setToScreen(int whichScreen) {
whichScreen = Math.max(0, Math.min(whichScreen, getChildCount()-1));
mCurScreen = whichScreen;
scrollTo(whichScreen*getWidth(), 0);
}

public int getCurScreen() {
return mCurScreen;
}

@Override
public void computeScroll() {
// TODO Auto-generated method stub
mScrollX = mScroller.getCurrX();
if (mScroller.computeScrollOffset()) {
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
updateWallpaperOffset();

postInvalidate();
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub

if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(event);

final int action = event.getAction();
final float x = event.getX();
final float y = event.getY();

switch (action) {
case MotionEvent.ACTION_DOWN:
Log.e(TAG, "event down!");
if (!mScroller.isFinished()){
mScroller.abortAnimation();
}
mLastMotionX = x;
break;

case MotionEvent.ACTION_MOVE:
int deltaX = (int)(mLastMotionX - x);
mLastMotionX = x;
scrollBy(deltaX, 0);
updateWallpaperOffset();
break;

case MotionEvent.ACTION_UP:
Log.e(TAG, "event : up");
// if (mTouchState == TOUCH_STATE_SCROLLING) {
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000);
int velocityX = (int) velocityTracker.getXVelocity();
Log.e(TAG, "velocityX:"+velocityX);

if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
// Fling enough to move left
Log.e(TAG, "snap left");
snapToScreen(mCurScreen - 1);
} else if (velocityX < -SNAP_VELOCITY
&& mCurScreen < getChildCount() - 1) {
// Fling enough to move right
Log.e(TAG, "snap right");
snapToScreen(mCurScreen + 1);
} else {
snapToDestination();
}
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
// }
mTouchState = TOUCH_STATE_REST;
break;
case MotionEvent.ACTION_CANCEL:
mTouchState = TOUCH_STATE_REST;
break;
}

return true;
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
// TODO Auto-generated method stub
Log.e(TAG, "onInterceptTouchEvent-slop:"+mTouchSlop);

final int action = ev.getAction();
if ((action == MotionEvent.ACTION_MOVE) &&
(mTouchState != TOUCH_STATE_REST)) {
return true;
}

final float x = ev.getX();
final float y = ev.getY();

switch (action) {
case MotionEvent.ACTION_MOVE:
final int xDiff = (int)Math.abs(mLastMotionX-x);
if (xDiff>mTouchSlop) {
mTouchState = TOUCH_STATE_SCROLLING;

}
break;

case MotionEvent.ACTION_DOWN:
mLastMotionX = x;
mLastMotionY = y;
mTouchState = mScroller.isFinished()? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;
break;

case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
mTouchState = TOUCH_STATE_REST;
break;
}

return mTouchState != TOUCH_STATE_REST;
}

private void updateWallpaperOffset() {
int scrollRange = getChildAt(getChildCount() - 1).getRight() - getWidth();
IBinder token = getWindowToken();
if (token != null) {
mWallpaperManager.setWallpaperOffsetSteps(1.0f / (getChildCount() - 1), 0 );
mWallpaperManager.setWallpaperOffsets(getWindowToken(),
Math.max(0.f, Math.min(getScrollX()/(float)scrollRange, 1.f)), 0);
}
}
}

package com.yao_guet;
import android.app.Activity;
import android.app.WallpaperManager;
import android.content.Context;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.Window;
import android.view.WindowManager;
public class WallPaperTest extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.wallpaper_test);
getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WALLPAPER);
}
@Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
// TODO Auto-generated method stub
return super.onKeyDown(keyCode, event);
}
}

<?xml version="1.0" encoding="utf-8"?>
<com.sf.test.ScrollLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/WallPaperTest"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="This is page 1" />
</LinearLayout>

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="This is page 2" />
</LinearLayout>

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="This is page 3" />
</LinearLayout>

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="This is page 4" />
</LinearLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="This is page 5" />
</LinearLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="This is page 6" />
</LinearLayout>

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="This is page 7" />
</LinearLayout>
</com.sf.test.ScrollLayout>