Java VelocityTracker類代碼示例

import android.view.VelocityTracker; //導入依賴的package包/類
/**
 * Start a fake drag of the pager.
 *
 * <p>A fake drag can be useful if you want to synchronize the motion of the ViewPager
 * with the touch scrolling of another view, while still letting the ViewPager
 * control the snapping motion and fling behavior. (e.g. parallax-scrolling tabs.)
 * Call {@link #fakeDragBy(float)} to simulate the actual drag motion. Call
 * {@link #endFakeDrag()} to complete the fake drag and fling as necessary.
 *
 * <p>During a fake drag the ViewPager will ignore all touch events. If a real drag
 * is already in progress, this method will return false.
 *
 * @return true if the fake drag began successfully, false if it could not be started.
 *
 * @see #fakeDragBy(float)
 * @see #endFakeDrag()
 */
public boolean beginFakeDrag() {
    if (mIsBeingDragged) {
        return false;
    }
    mFakeDragging = true;
    setScrollState(SCROLL_STATE_DRAGGING);
    mInitialMotionX = mLastMotionX = 0;
    if (mVelocityTracker == null) {
        mVelocityTracker = VelocityTracker.obtain();
    } else {
        mVelocityTracker.clear();
    }
    final long time = SystemClock.uptimeMillis();
    final MotionEvent ev = MotionEvent.obtain(time, time, MotionEvent.ACTION_DOWN, 0, 0, 0);
    mVelocityTracker.addMovement(ev);
    ev.recycle();
    mFakeDragBeginTime = time;
    return true;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
public static void velocityTrackerPointerUpCleanUpIfNecessary(MotionEvent ev,
                                                              VelocityTracker tracker) {

    // Check the dot product of current velocities.
    // If the pointer that left was opposing another velocity vector, clear.
    tracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
    final int upIndex = ev.getActionIndex();
    final int id1 = ev.getPointerId(upIndex);
    final float x1 = tracker.getXVelocity(id1);
    final float y1 = tracker.getYVelocity(id1);
    for (int i = 0, count = ev.getPointerCount(); i < count; i++) {
        if (i == upIndex)
            continue;

        final int id2 = ev.getPointerId(i);
        final float x = x1 * tracker.getXVelocity(id2);
        final float y = y1 * tracker.getYVelocity(id2);

        final float dot = x + y;
        if (dot < 0) {
            tracker.clear();
            break;
        }
    }
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
/**
 * Start a fake drag of the pager.
 *
 * @return true if the fake drag began successfully, false if it could not be started.
 */
public boolean beginFakeDrag() {
    if (mIsBeingDragged) {
        return false;
    }
    mFakeDragging = true;
    setScrollState(SCROLL_STATE_DRAGGING);
    if (isHorizontal()) {
        mInitialMotionX = mLastMotionX = 0;
    } else {
        mInitialMotionY = mLastMotionY = 0;
    }
    if (mVelocityTracker == null) {
        mVelocityTracker = VelocityTracker.obtain();
    } else {
        mVelocityTracker.clear();
    }
    final long time = SystemClock.uptimeMillis();
    final MotionEvent ev = MotionEvent.obtain(time, time, MotionEvent.ACTION_DOWN, 0, 0, 0);
    mVelocityTracker.addMovement(ev);
    ev.recycle();
    mFakeDragBeginTime = time;
    return true;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
/**
 * Start a fake drag of the pager.
 * <p/>
 * <p>A fake drag can be useful if you want to synchronize the motion of the ViewPager
 * with the touch scrolling of another view, while still letting the ViewPager
 * control the snapping motion and fling behavior. (e.g. parallax-scrolling tabs.)
 * Call {@link #fakeDragBy(float)} to simulate the actual drag motion. Call
 * {@link #endFakeDrag()} to complete the fake drag and fling as necessary.
 * <p/>
 * <p>During a fake drag the ViewPager will ignore all touch events. If a real drag
 * is already in progress, this method will return false.
 *
 * @return true if the fake drag began successfully, false if it could not be started.
 * @see #fakeDragBy(float)
 * @see #endFakeDrag()
 */
public boolean beginFakeDrag() {
    if (mIsBeingDragged) {
        return false;
    }
    mFakeDragging = true;
    setScrollState(SCROLL_STATE_DRAGGING);
    mInitialMotionY = mLastMotionY = 0;
    if (mVelocityTracker == null) {
        mVelocityTracker = VelocityTracker.obtain();
    } else {
        mVelocityTracker.clear();
    }
    final long time = SystemClock.uptimeMillis();
    final MotionEvent ev = MotionEvent.obtain(time, time, MotionEvent.ACTION_DOWN, 0, 0, 0);
    mVelocityTracker.addMovement(ev);
    ev.recycle();
    mFakeDragBeginTime = time;
    return true;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
/**
 * End a fake drag of the pager.
 *
 * @see #beginFakeDrag()
 * @see #fakeDragBy(float)
 */
public void endFakeDrag() {
    if (!mFakeDragging) {
        throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");
    }

    final VelocityTracker velocityTracker = mVelocityTracker;
    velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
    int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(
            velocityTracker, mActivePointerId);
    mPopulatePending = true;
    final int height = getClientHeight();
    final int scrollY = getScrollY();
    final ItemInfo ii = infoForCurrentScrollPosition();
    final int currentPage = ii.position;
    final float pageOffset = (((float) scrollY / height) - ii.offset) / ii.heightFactor;
    final int totalDelta = (int) (mLastMotionY - mInitialMotionY);
    int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity,
            totalDelta);
    setCurrentItemInternal(nextPage, true, true, initialVelocity);
    endDrag();

    mFakeDragging = false;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
/**
 * Start a fake drag of the pager.
 * <p/>
 * <p>A fake drag can be useful if you want to synchronize the motion of the ViewPager
 * with the touch scrolling of another view, while still letting the ViewPager
 * control the snapping motion and fling behavior. (e.g. parallax-scrolling tabs.)
 * Call {@link #fakeDragBy(float)} to simulate the actual drag motion. Call
 * {@link #endFakeDrag()} to complete the fake drag and fling as necessary.
 * <p/>
 * <p>During a fake drag the ViewPager will ignore all touch events. If a real drag
 * is already in progress, this method will return false.
 *
 * @return true if the fake drag began successfully, false if it could not be started.
 * @see #fakeDragBy(float)
 * @see #endFakeDrag()
 */
public boolean beginFakeDrag() {
    if (mIsBeingDragged) {
        return false;
    }
    mFakeDragging = true;
    setScrollState(SCROLL_STATE_DRAGGING);
    if (isHorizontalDirection()) {
        mInitialMotionX = mLastMotionX = 0;
    } else if (isVerticalDirection()) {
        mInitialMotionY = mLastMotionY = 0;
    }
    if (mVelocityTracker == null) {
        mVelocityTracker = VelocityTracker.obtain();
    } else {
        mVelocityTracker.clear();
    }
    final long time = SystemClock.uptimeMillis();
    final MotionEvent ev = MotionEvent.obtain(time, time, MotionEvent.ACTION_DOWN, 0, 0, 0);
    mVelocityTracker.addMovement(ev);
    ev.recycle();
    mFakeDragBeginTime = time;
    return true;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
private void endFakeDragHorizontally() {
    if (mAdapter != null) {
        final VelocityTracker velocityTracker = mVelocityTracker;
        velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
        int initialVelocity = (int) VelocityTrackerCompat.getXVelocity(
                velocityTracker, mActivePointerId);
        mPopulatePending = true;
        final int width = getClientWidth();
        final int scrollX = getScrollX();
        final ItemInfo ii = infoForCurrentScrollPosition();
        final int currentPage = ii.position;
        final float pageOffset = (((float) scrollX / width) - ii.offset) / ii.widthFactor;
        final int totalDelta = (int) (mLastMotionX - mInitialMotionX);
        int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity,
                totalDelta);
        setCurrentItemInternal(nextPage, true, true, initialVelocity);
    }
    endDrag();

    mFakeDragging = false;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
private void endFakeDragVertically() {
    if (mAdapter != null) {
        final VelocityTracker velocityTracker = mVelocityTracker;
        velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
        int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(
                velocityTracker, mActivePointerId);
        mPopulatePending = true;
        final int height = getClientHeight();
        final int scrollY = getScrollY();
        final ItemInfo ii = infoForCurrentScrollPosition();
        final int currentPage = ii.position;
        final float pageOffset = (((float) scrollY / height) - ii.offset) / ii.heightFactor;
        final int totalDelta = (int) (mLastMotionY - mInitialMotionY);
        int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity,
                totalDelta);
        setCurrentItemInternal(nextPage, true, true, initialVelocity);
    }
    endDrag();

    mFakeDragging = false;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
public ResolverDrawerLayout(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);

    final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ResolverDrawerLayout,
            defStyleAttr, 0);
    mMaxWidth = a.getDimensionPixelSize(R.styleable.ResolverDrawerLayout_android_maxWidth, -1);
    mMaxCollapsedHeight = a.getDimensionPixelSize(
            R.styleable.ResolverDrawerLayout_maxCollapsedHeight, 0);
    mMaxCollapsedHeightSmall = a.getDimensionPixelSize(
            R.styleable.ResolverDrawerLayout_maxCollapsedHeightSmall,
            mMaxCollapsedHeight);
    a.recycle();

    mScrollIndicatorDrawable = context.getDrawable(R.drawable.scroll_indicator_material);

    mScroller = new OverScroller(context, AnimationUtils.loadInterpolator(context,
            android.R.interpolator.decelerate_quint));
    mVelocityTracker = VelocityTracker.obtain();

    final ViewConfiguration vc = ViewConfiguration.get(context);
    mTouchSlop = vc.getScaledTouchSlop();
    mMinFlingVelocity = vc.getScaledMinimumFlingVelocity();

    setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
private float getXVelocity() {
    float xVelocity = 0;
    Class viewpagerClass = ViewPager.class;
    try {
        Field velocityTrackerField = viewpagerClass.getDeclaredField("mVelocityTracker");
        velocityTrackerField.setAccessible(true);
        VelocityTracker velocityTracker = (VelocityTracker) velocityTrackerField.get(this);

        Field activePointerIdField = viewpagerClass.getDeclaredField("mActivePointerId");
        activePointerIdField.setAccessible(true);

        Field maximumVelocityField = viewpagerClass.getDeclaredField("mMaximumVelocity");
        maximumVelocityField.setAccessible(true);
        int maximumVelocity = maximumVelocityField.getInt(this);

        velocityTracker.computeCurrentVelocity(1000, maximumVelocity);
        xVelocity = VelocityTrackerCompat.getXVelocity(velocityTracker, activePointerIdField.getInt(this));
    } catch (Exception e) {
    }
    return xVelocity;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
private void onTouchRelease() {
    final StackCardsView.LayoutParams lp = (StackCardsView.LayoutParams) mTouchChild.getLayoutParams();
    if (lp.fastDismissAllowed) {
        final VelocityTracker velocityTracker2 = mVelocityTracker;
        velocityTracker2.computeCurrentVelocity(1000, mMaxVelocity);
        float xv = velocityTracker2.getXVelocity(mActivePointerId);
        float yv = velocityTracker2.getYVelocity(mActivePointerId);
        if (doFastDisappear(xv, yv)) {
            resetTouch();
            return;
        }
    }
    if (isDistanceAllowDismiss() && isDirectionAllowDismiss()) {
        doSlowDisappear();
    } else {
        animateToInitPos();
    }
    resetTouch();
    mSwipeView.onCoverStatusChanged(isCoverIdle());
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
@Override
public boolean onTouchEvent(MotionEvent event) {
    if (mVirtualCount == 0 || !isEnabled()) {
        return super.onTouchEvent(event);
    }
    if (event.getAction() == MotionEvent.ACTION_DOWN && event.getEdgeFlags() != 0) {
        return false;
    }
    if (mVelocityTracker == null) {
        mVelocityTracker = VelocityTracker.obtain();
    }
    mVelocityTracker.addMovement(event);
    final int action = event.getAction() & MotionEventCompat.ACTION_MASK;
    if (action == MotionEvent.ACTION_MOVE) {
        handleTouchActionMove(event);
    } else {
        if (action == MotionEvent.ACTION_DOWN) {
            handleTouchActionDown(event);
        }
        if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
            handleTouchActionUp(event);
        }
    }
    return true;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
@Override
public boolean onTouchEvent(MotionEvent event) {

    if (mVelocityTracker == null) {
        mVelocityTracker = VelocityTracker.obtain();
    }
    mVelocityTracker.addMovement(event);
    switch (event.getAction()) {
        case MotionEvent.ACTION_CANCEL:
            actionCancel(event);
            break;
        case MotionEvent.ACTION_DOWN:
            actionDown(event);
            break;
        case MotionEvent.ACTION_MOVE:
            actionMove(event);
            break;
        case MotionEvent.ACTION_UP:
            actionUp(event);
            break;
        default:
            break;
    }
    invalidateView();
    return true;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
/**
 * End a fake drag of the pager.
 *
 * @see #beginFakeDrag()
 * @see #fakeDragBy(float)
 */
public void endFakeDrag() {
    if (!mFakeDragging) {
        throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");
    }

    final VelocityTracker velocityTracker = mVelocityTracker;
    velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
    int initialVelocity = (int) VelocityTrackerCompat.getXVelocity(
            velocityTracker, mActivePointerId);
    mPopulatePending = true;
    final int width = getClientWidth();
    final int scrollX = getScrollX();
    final ItemInfo ii = infoForCurrentScrollPosition();
    final int currentPage = ii.position;
    final float pageOffset = (((float) scrollX / width) - ii.offset) / ii.widthFactor;
    final int totalDelta = (int) (mLastMotionX - mInitialMotionX);
    int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity,
            totalDelta);
    setCurrentItemInternal(nextPage, true, true, initialVelocity);
    endDrag();

    mFakeDragging = false;
}
 

import android.view.VelocityTracker; //導入依賴的package包/類
public boolean beginFakeDrag() {
    if (mIsBeingDragged) {
        return false;
    }
    mFakeDragging = true;
    setScrollState(SCROLL_STATE_DRAGGING);
    mInitialMotionX = mLastMotionX = 0;
    if (mVelocityTracker == null) {
        mVelocityTracker = VelocityTracker.obtain();
    } else {
        mVelocityTracker.clear();
    }
    final long time = SystemClock.uptimeMillis();
    final MotionEvent ev = MotionEvent.obtain(time, time, MotionEvent.ACTION_DOWN, 0, 0, 0);
    mVelocityTracker.addMovement(ev);
    ev.recycle();
    mFakeDragBeginTime = time;
    return true;
}