仿android桌面左右滑动

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; } @Override protected void onRestoreInstanceState(Parcelable state) { SavedState savedState = (SavedState) state; super.onRestoreInstanceState(savedState.getSuperState()); if (savedState.currentScreen != -1) { mCurrentScreen = savedState.currentScreen; } } @Override protected 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; } } @Override protected 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; } } } @Override public 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; } } @Override public 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; } @Override public 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(); } @Override public 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.ShortcutDock xmlns: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>

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