Workspace界面模拟

>模拟WorkSpace界面的实现代码

>>onMeasure onLayout初始化界面

>>onInterceptTouchEvent() onTouchEvent()实现左右滑动

/** * @author Lean  @date:2014-10-30   */public class MyScrollLayout extends ViewGroup{private static final int TOUCH_STATE_SCROLLING = 0;private static final int TOUCH_STATE_REST = 1;private static final int SNAP_VELOCITY = 700;private Scroller mScroller;private int mTouchSlop;private int mTouchState;private VelocityTracker mVelocityTracker;private float mDownX;private int mCurrenScreen;public MyScrollLayout(Context context, AttributeSet attrs) {super(context, attrs);mScroller=new Scroller(context);mTouchSlop=ViewConfiguration.get(context).getScaledTouchSlop();}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);int widthMode=MeasureSpec.getMode(widthMeasureSpec);int heightMode=MeasureSpec.getMode(heightMeasureSpec);if (widthMode!=MeasureSpec.EXACTLY||heightMode!=MeasureSpec.EXACTLY) {throw new IllegalStateException("you must improve a exacty child view !");}int width=MeasureSpec.getSize(widthMeasureSpec);final int childCount=getChildCount();for (int i = 0; i <childCount; i++) {getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);}scrollTo(mCurrenScreen*width, 0);}@Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b) {if (changed) {int childLeft=0;final int childCount=getChildCount();for (int i = 0; i < childCount; i++) {View childView=getChildAt(i);getChildAt(i).layout(childLeft, 0, childLeft+getWidth(),childView.getMeasuredHeight());childLeft+=getWidth();}}}@Overridepublic boolean onInterceptTouchEvent(MotionEvent ev) {int action=ev.getAction();if (action==MotionEvent.ACTION_MOVE&&(mTouchState!=TOUCH_STATE_REST)) {return true;}switch (action) {case MotionEvent.ACTION_DOWN:mDownX=ev.getRawX();mTouchState=mScroller.isFinished()?TOUCH_STATE_REST:TOUCH_STATE_SCROLLING;break;case MotionEvent.ACTION_MOVE:float deltaX=Math.abs(mDownX-ev.getRawX());if (mTouchSlop<deltaX) {mTouchState=TOUCH_STATE_SCROLLING;}break;case MotionEvent.ACTION_UP:case MotionEvent.ACTION_CANCEL:mTouchState=TOUCH_STATE_REST;break;default:break;}return mTouchState!=TOUCH_STATE_REST;}@Overridepublic boolean onTouchEvent(MotionEvent event) {createVelocity(event);switch (event.getAction()) {case MotionEvent.ACTION_DOWN:if (!mScroller.isFinished()) {mScroller.abortAnimation();}mDownX=event.getRawX();break;case MotionEvent.ACTION_MOVE:int deltaX=(int) (mDownX-event.getRawX());mDownX=event.getRawX();scrollBy(deltaX, 0);break;case MotionEvent.ACTION_UP:mVelocityTracker.computeCurrentVelocity(1000);int velocityX=(int) mVelocityTracker.getXVelocity();if (velocityX>SNAP_VELOCITY&&mCurrenScreen>0) {snapToScreen(mCurrenScreen-1);}else if (velocityX<-SNAP_VELOCITY&&mCurrenScreen<getChildCount()-1) {snapToScreen(mCurrenScreen+1);}else {snapToDestination();}recycleVelocity();mTouchState=TOUCH_STATE_REST;break;case MotionEvent.ACTION_CANCEL:mTouchState=TOUCH_STATE_REST;break;default:break;}return true;}private void snapToScreen(int whichScreen) {whichScreen=Math.max(0, Math.min(whichScreen,getChildCount()-1));if (getScrollX()!=(whichScreen*getWidth())) {int deltaX=whichScreen*getWidth()-getScrollX();mScroller.startScroll(getScrollX(),0, deltaX, 0,Math.abs(deltaX)*2);mCurrenScreen=whichScreen;invalidate();}}private void snapToDestination() {int whichScreen=(getScrollX()+getWidth()/2)/getWidth();snapToScreen(whichScreen);}@Overridepublic void computeScroll() {if (mScroller.computeScrollOffset()) {scrollTo(mScroller.getCurrX(),mScroller.getCurrY());invalidate();}}private void recycleVelocity() {if (mVelocityTracker!=null) {mVelocityTracker.recycle();mVelocityTracker=null;}}private void createVelocity(MotionEvent event) {if (mVelocityTracker==null) {mVelocityTracker=VelocityTracker.obtain();}mVelocityTracker.addMovement(event);}}