android.graphics.PointF#length ( )源码实例Demo

@Override
public boolean onTouchEvent(MotionEvent evt) {
    switch (evt.getAction()) {
        case MotionEvent.ACTION_DOWN:
            // 记录按下时候的坐标
            downPoint.x = evt.getX();
            downPoint.y = evt.getY();
            if (this.getChildCount() > 1) {
                //有内容，多于1个时
                // 通知其父控件，现在进行的是本控件的操作，不允许拦截
                getParent().requestDisallowInterceptTouchEvent(true);
            }
            break;
        case MotionEvent.ACTION_MOVE:
            if (this.getChildCount() > 1) {
                //有内容，多于1个时
                // 通知其父控件，现在进行的是本控件的操作，不允许拦截
                getParent().requestDisallowInterceptTouchEvent(true);
            }
            break;
        case MotionEvent.ACTION_UP:
            // 在up时判断是否按下和松手的坐标为一个点
            if (PointF.length(evt.getX() - downPoint.x, evt.getY() - downPoint.y) < (float) 5.0) {
                onSingleTouch(this);
                return true;
            }
            break;
        default:
            break;
    }
    return super.onTouchEvent(evt);
}
 

/**
 * Handles the touch events that shows the workspace when clicking outside the bounds of the
 * touch delegate target view.
 */
private boolean handleTouchEvent(MotionEvent ev) {
    switch (ev.getAction()) {
        case MotionEvent.ACTION_DOWN:
            // Check if the touch is outside touch delegate target view
            View touchDelegateTargetView = getTouchDelegateTargetView();
            float leftBoundPx = touchDelegateTargetView.getLeft();
            if (ev.getX() < leftBoundPx ||
                    ev.getX() > (touchDelegateTargetView.getWidth() + leftBoundPx)) {
                mLastTouchDownPosPx.set((int) ev.getX(), (int) ev.getY());
            }
            break;
        case MotionEvent.ACTION_UP:
            if (mLastTouchDownPosPx.x > -1) {
                ViewConfiguration viewConfig = ViewConfiguration.get(getContext());
                float dx = ev.getX() - mLastTouchDownPosPx.x;
                float dy = ev.getY() - mLastTouchDownPosPx.y;
                float distance = PointF.length(dx, dy);
                if (distance < viewConfig.getScaledTouchSlop()) {
                    // The background was clicked, so just go home
                    Launcher.getLauncher(getContext()).showWorkspace(true);
                    return true;
                }
            }
            // Fall through
        case MotionEvent.ACTION_CANCEL:
            mLastTouchDownPosPx.set(-1, -1);
            break;
    }
    return false;
}
 

static Path createPath(PointF startPoint, PointF endPoint, PointF cp1, PointF cp2) {
  Path path = new Path();
  path.moveTo(startPoint.x, startPoint.y);

  if (cp1 != null && cp1.length() != 0 && cp2 != null && cp2.length() != 0) {
    path.cubicTo(
        startPoint.x + cp1.x, startPoint.y + cp1.y,
        endPoint.x + cp2.x, endPoint.y + cp2.y,
        endPoint.x, endPoint.y);
  } else {
    path.lineTo(endPoint.x, endPoint.y);
  }
  return path;
}
 

public static Path createPath(PointF startPoint, PointF endPoint, PointF cp1, PointF cp2) {
  Path path = new Path();
  path.moveTo(startPoint.x, startPoint.y);

  if (cp1 != null && cp2 != null && (cp1.length() != 0 || cp2.length() != 0)) {
    path.cubicTo(
        startPoint.x + cp1.x, startPoint.y + cp1.y,
        endPoint.x + cp2.x, endPoint.y + cp2.y,
        endPoint.x, endPoint.y);
  } else {
    path.lineTo(endPoint.x, endPoint.y);
  }
  return path;
}
 

/** Calculates the distance between the 2 current pointers */
private float distance(MotionEvent event) {
    if (event.getPointerCount() < 2) {
        return 0;
    }
    return PointF.length(event.getX(POINTER1) - event.getX(POINTER2), //
            event.getY(POINTER1) - event.getY(POINTER2));
}
 

private float xyToDegrees(float x, float y) {
    float distanceFromCenter = PointF.length((x - 0.5f), (y - 0.5f));
    if (distanceFromCenter < 0.15f
            || distanceFromCenter > 0.5f) { // ignore center and out of bounds events
        return Float.NaN;
    } else {
        return (float) Math.toDegrees(Math.atan2(x - 0.5f, y - 0.5f));
    }
}
 

private void normalizeVector(PointF point) {
    final float abs = point.length();
    point.set(point.x / abs, point.y / abs);
}
 

public boolean satisfyMoveDismissCondition(MotionEvent event) {
    return PointF.length(event.getRawX() - mDownPointF.x, event.getRawY() - mDownPointF.y) > mMoveHiddenThreshold;
}
 

private void normalizeVector(PointF point) {
    final float abs = point.length();
    point.set(point.x / abs, point.y / abs);
}
 

/**
 * Test if a MotionEvent with the given start and end offsets
 * can be considered as a "click".
 * @param upEvent The final finger-up event.
 * @param xDown   The x-offset of the down event.
 * @param yDown   The y-offset of the down event.
 * @param xUp     The x-offset of the up event.
 * @param yUp     The y-offset of the up event.
 * @return true if it's a click, false otherwise
 */
private boolean isClick(MotionEvent upEvent, float xDown, float yDown, float xUp, float yUp) {
    if (upEvent == null) return false;
    long time = upEvent.getEventTime() - upEvent.getDownTime();
    float distance = PointF.length( //
            xDown - xUp, //
            yDown - yUp);
    return time < MAX_CLICK_TIME && distance < MAX_CLICK_DISTANCE;
}
 

/**
 * Get the euclidean distance between two points
 *
 * @param firstPoint PointF object
 * @param secondPoint PointF object
 * @return float value representing the distance in a straight line between two points
 */
public static float euclideanDistance(PointF firstPoint, PointF secondPoint) {
    return PointF.length(secondPoint.x - firstPoint.x, secondPoint.y - firstPoint.y);
}