自定义组件：ScrollLayout

import android.content.Context;import android.graphics.Canvas;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 * @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;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 stubmScroller = 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 stubif (changed) {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;}}}}    @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;    }    @Overridepublic void computeScroll() {// TODO Auto-generated method stubif (mScroller.computeScrollOffset()) {scrollTo(mScroller.getCurrX(), mScroller.getCurrY());postInvalidate();}}@Overridepublic boolean onTouchEvent(MotionEvent event) {// TODO Auto-generated method stubif (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);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;}@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;}}

import android.app.Activity;import android.os.Bundle;public class ScrollLayoutTest extends Activity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);    }}

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  android:layout_width="fill_parent"  android:layout_height="fill_parent"  android:orientation="vertical"  >  <TextView android:layout_width="fill_parent"  android:layout_height="wrap_content"  android:text="text text"  android:textColor="@android:color/white"  />  <LinearLayout  android:layout_width="fill_parent"  android:layout_height="fill_parent"  android:orientation="horizontal"  >  <TextView android:layout_width="fill_parent"  android:layout_height="fill_parent"  android:text="ScrollLayout"  android:textColor="@android:color/white"  android:layout_weight="1"  />  <com.yao_guet.test.ScrollLayout  android:id="@+id/ScrollLayoutTest"  android:layout_width="fill_parent"  android:layout_height="fill_parent"  android:layout_weight="1"  ><LinearLayout  android:background="#FF00"  android:layout_width="fill_parent"  android:layout_height="fill_parent"></LinearLayout>  <FrameLayout  android:background="#F0F0"  android:layout_width="fill_parent"  android:layout_height="fill_parent"></FrameLayout>  <FrameLayout  android:background="#F00F"  android:layout_width="fill_parent"  android:layout_height="fill_parent">  </FrameLayout>  <LinearLayout  android:background="#FF00"  android:layout_width="fill_parent"  android:layout_height="fill_parent">  <Button  android:layout_width="wrap_content"  android:layout_height="wrap_content"  android:text="Button1" />  </LinearLayout><LinearLayout  android:layout_width="wrap_content"  android:layout_height="wrap_content">  <Button  android:layout_width="wrap_content"  android:layout_height="wrap_content"  android:text="Button2" />  </LinearLayout></com.yao_guet.test.ScrollLayout></LinearLayout></LinearLayout>

Android中使用GridView分页显示系统所安装的应用，支持拖动与手势滑动
http://blog.csdn.net/Yao_GUET/archive/2011/05/05/6397197.aspx
提取Launcher中的WorkSapce，可以左右滑动切换屏幕页面的类
http://blog.csdn.net/yao_guet/article/details/6393962