仿android案頭左右滑動

public class ShortcutDock extends LinearLayout {

private static final int INVALID_SCREEN = -1;

private int mScrollingSpeed = 600;

private int mScrollingBounce = 50;

private boolean mFirstLayout = true;

private static final int SNAP_VELOCITY = 300;

private int mCurrentScreen;

private int mNextScreen = INVALID_SCREEN;

private Scroller mScroller;

private VelocityTracker mVelocityTracker;

private float mLastMotionX;

private float mLastMotionY;

private final static int TOUCH_STATE_REST = 0;

private final static int TOUCH_STATE_SCROLLING = 1;

private int mTouchState = TOUCH_STATE_REST;

private int mMaximumVelocity;

private int mTouchSlop;

public ShortcutDock(Context context, AttributeSet attrs) {super(context, attrs);setHapticFeedbackEnabled(false);initWorkspace();requestFocus();}private void initWorkspace() {mScroller = new Scroller(getContext());mCurrentScreen = 1;final ViewConfiguration configuration = ViewConfiguration.get(getContext());mTouchSlop = configuration.getScaledTouchSlop();mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();}int getCurrentScreen() {return mCurrentScreen;}protected Parcelable onSaveInstanceState() {final SavedState state = new SavedState(super.onSaveInstanceState());state.currentScreen = mCurrentScreen;return state;}@Overrideprotected void onRestoreInstanceState(Parcelable state) {SavedState savedState = (SavedState) state;super.onRestoreInstanceState(savedState.getSuperState());if (savedState.currentScreen != -1) {mCurrentScreen = savedState.currentScreen;}}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);final int width = MeasureSpec.getSize(widthMeasureSpec);final int widthMode = MeasureSpec.getMode(widthMeasureSpec);if (widthMode != MeasureSpec.EXACTLY) {throw new IllegalStateException("ShortcutDock can only be used in EXACTLY mode.");}final int heightMode = MeasureSpec.getMode(heightMeasureSpec);if (heightMode != MeasureSpec.EXACTLY) {throw new IllegalStateException("ShortcutDock can only be used in EXACTLY mode.");}final int count = getChildCount();for (int i = 0; i < count; i++) {getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);}if (mFirstLayout) {setHorizontalScrollBarEnabled(false);scrollTo(mCurrentScreen * width, 0);mScroller.startScroll(0, 0, mCurrentScreen * width, 0, 0);setHorizontalScrollBarEnabled(false);mFirstLayout = false;}}@Overrideprotected void onLayout(boolean changed, int left, int top, int right,int bottom) {int childLeft = 0;final int count = getChildCount();for (int i = 0; i < count; i++) {final View child = getChildAt(i);if (child.getVisibility() != View.GONE) {final int childWidth = child.getMeasuredWidth();child.layout(childLeft, 0, childLeft + childWidth, child.getMeasuredHeight());childLeft += childWidth;}}}@Overridepublic void computeScroll() {if (mScroller.computeScrollOffset()) {scrollTo(mScroller.getCurrX(), mScroller.getCurrY());postInvalidate();} else if (mNextScreen != INVALID_SCREEN) {mCurrentScreen = Math.max(0, Math.min(mNextScreen,getChildCount() - 1));mNextScreen = INVALID_SCREEN;}}@Overridepublic boolean onInterceptTouchEvent(MotionEvent ev) {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(x - mLastMotionX);final int yDiff = (int) Math.abs(y - mLastMotionY);final int touchSlop = mTouchSlop;boolean xMoved = xDiff > touchSlop;boolean yMoved = yDiff > touchSlop;if (xMoved || yMoved) {if (xDiff > yDiff) {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;}@Overridepublic boolean onTouchEvent(MotionEvent ev) {if (mVelocityTracker == null) {mVelocityTracker = VelocityTracker.obtain();}mVelocityTracker.addMovement(ev);final int action = ev.getAction();final float x = ev.getX();switch (action) {case MotionEvent.ACTION_DOWN:if (!mScroller.isFinished()) {mScroller.abortAnimation();}mLastMotionX = x;break;case MotionEvent.ACTION_MOVE:final int deltaX = (int) (mLastMotionX - x);mLastMotionX = x;int tScrollX = getScrollX();if (deltaX < 0) {if (tScrollX > -mScrollingBounce) {scrollBy(Math.min(deltaX, mScrollingBounce), 0);}} else if (deltaX > 0) {final int availableToScroll = getChildAt(getChildCount() - 1).getRight()- tScrollX - getWidth() + mScrollingBounce;if (availableToScroll > 0) {scrollBy(deltaX, 0);}}break;case MotionEvent.ACTION_UP:final VelocityTracker velocityTracker = mVelocityTracker;velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);int velocityX = (int) velocityTracker.getXVelocity();if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {snapToScreen(mCurrentScreen - 1);} else if (velocityX < -SNAP_VELOCITY&& mCurrentScreen < getChildCount() - 1) {snapToScreen(mCurrentScreen + 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;}private void snapToDestination() {final int screenWidth = getWidth();final int whichScreen = (getScrollX() + (screenWidth / 2))/ screenWidth;snapToScreen(whichScreen);}void snapToScreen(int whichScreen) {whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));boolean changingScreens = whichScreen != mCurrentScreen;mNextScreen = whichScreen;View focusedChild = getFocusedChild();if (focusedChild != null && changingScreens&& focusedChild == getChildAt(mCurrentScreen)) {focusedChild.clearFocus();}final int screenDelta = Math.abs(whichScreen - mCurrentScreen);int durationOffset = 1;if (screenDelta == 0) {durationOffset = 400;}final int duration = mScrollingSpeed + durationOffset;final int newX = whichScreen * getWidth();final int delta = newX - getScrollX();mScroller.startScroll(getScrollX(), 0, delta, 0, duration);invalidate();}public static class SavedState extends BaseSavedState {int currentScreen = -1;SavedState(Parcelable superState) {super(superState);}private SavedState(Parcel in) {super(in);currentScreen = in.readInt();}@Overridepublic void writeToParcel(Parcel out, int flags) {super.writeToParcel(out, flags);out.writeInt(currentScreen);}public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {public SavedState createFromParcel(Parcel in) {return new SavedState(in);}public SavedState[] newArray(int size) {return new SavedState[size];}};}}xml:<com.shortcutdock.demo.ShortcutDockxmlns:shortcut="http://schemas.android.com/apk/res/com.shortcutdock.demo"android:layout_gravity="right|center" android:orientation="horizontal"android:id="@+id/shortcut_bar" android:layout_width="fill_parent"android:layout_height="fill_parent"></com.shortcutdock.demo.ShortcutDock>