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：

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

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.

The offset along the Y dimension, from 0 to 1.

修改了之前ScrollLayout的类，让它支持显示系统背景，并且拖动的时候背景也跟着拖动，跟Launcher中的效果一致。。。基本类文件ScrollLayout.java

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 stubmWallpaperManager = WallpaperManager.getInstance(context);mScroller = new Scroller(context);mCurScreen = mDefaultScreen;mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();}@Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b) {// TODO Auto-generated method stubLog.e(TAG, "onLayout");int childLeft = 0;final int childCount = getChildCount();for (int i=0; i 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;}@Overridepublic boolean onInterceptTouchEvent(MotionEvent ev) {// TODO Auto-generated method stubLog.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);        }    }}

测试代码WallPaperTest.java：

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 {@Overrideprotected void onCreate(Bundle savedInstanceState) {// TODO Auto-generated method stubsuper.onCreate(savedInstanceState);this.requestWindowFeature(Window.FEATURE_NO_TITLE);setContentView(R.layout.wallpaper_test);getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WALLPAPER);}@Overrideprotected void onDestroy() {// TODO Auto-generated method stubsuper.onDestroy();}@Overridepublic boolean onKeyDown(int keyCode, KeyEvent event) {// TODO Auto-generated method stubreturn super.onKeyDown(keyCode, event);}}

layout布局文件wallpaper_test.xml：

<?xml version="1.0" encoding="utf-8"?>

然后记得修改AndroidManifest.xml文件。。。

android:label="@string/app_name"

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

public void setWallpaperOffsetSteps (float xStep, float yStep)

Parameters

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

Parameters

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