ScrollLayout.xml檔案
package com.teleca.robin;import android.content.Context;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，可以左右滑動切換畫面的類 * * @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;}}}}@Overrideprotected 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 scrollLayoutfinal 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 pagewhichScreen = 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 leftLog.e(TAG, "snap left");snapToScreen(mCurScreen - 1);} else if (velocityX < -SNAP_VELOCITY&& mCurScreen < getChildCount() - 1) {// Fling enough to move rightLog.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;}}
