我一直在玩动作事件和拖拽（所以我不会把手指从屏幕上拿下来——这不是一次投掷）。问题是它只检测到第二个、第三个、第四个等等，当我的手指移动过上下拖动开始和结束的点时，拖动向下或向上移动。
见下面的代码。向上拖动时计数等于2，向下拖动时计数等于1。然而，它只在我向上移动手指（计数2）然后向下移动超过开始向上移动的点（计数1）时才起作用，而不是在等于2的点之前。当我向上移动时，它继续起作用。只有当我向下移动超过改变方向的点时，它才起作用。但它为什么不在这些点之前将其识别为阻力，因为在这些方向上的任何移动都应该是阻力。我该如何解决？
下面是我测试它的简单代码：
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
oldX = (int) event.getRawX();
oldY = (int) event.getRawY();
break;
case MotionEvent.ACTION_MOVE:
posY = (int) event.getRawY();
posX = (int) event.getRawX();
diffPosY = posY - oldY;
diffPosX = posX - oldX;
if (diffPosY > 0){//down
count = 1;
}
else//up
{
count = 2;
}
break;
最佳答案
如果我理解您试图正确执行的操作，我认为您需要在您的oldX中更新oldY和case MotionEvent.ACTION_MOVE:，在您使用它设置diffPosY和diffPosX之后，因为您当前仅在触摸开始时设置oldX和oldY。因此，在设置diffPosY和diffPosX之后，添加：
oldX = posX;
oldY = posY;
更新
因为动作事件是经常处理的，所以你可能想引入一些触控斜坡来解释这样一个事实：当你把手指放在屏幕上时，你可能会在你向上移动之前稍微向下移动一点而没有意识到，如果你慢慢刷卡，你可能会不经意地朝着你认为的方向轻轻刷卡。这看起来就像你在下面的评论里看到的一样。下面的代码应该有助于解决这个问题，但会使它对方向的变化反应稍微慢一点：
// Get the distance in pixels that a touch can move before we
// decide it's a drag rather than just a touch. This also prevents
// a slight movement in a different direction to the direction
// the user intended to move being considered a drag in that direction.
// Note that the touchSlop varies on each device because of different
// pixel densities.
ViewConfiguration vc = ViewConfiguration.get(context);
int touchSlop = vc.getScaledTouchSlop();
// So we can detect changes of direction. We need to
// keep moving oldY as we use that as the reference to see if we
// are dragging up or down.
if (posY - oldY > touchSlop) {
// The drag has moved far enough up the Y axis for us to
// decide it's a drag, so set oldY to a new position just below
// the current drag position. By setting oldY just below the
// current drag position we make sure that if while dragging the
// user stops their drag and accidentally moves down just by a
// pixel or two (which is easily done even when the user thinks
// their finger isn't moving), we don't count it as a change of
// direction, so we use half the touchSlop figure as a small
// buffer to allow a small movement down before we consider it
// a change of direction.
oldY = posY - (touchSlop / 2);
} else if (posY - oldY < -touchSlop) {
// The drag has moved far enough down the Y axis for us to
// decide it's a drag, so set oldY to a new position just above
// the current drag position. This time, we set oldY just above the
// current drag position.
oldY = posY + (touchSlop / 2);
}