Question

我想捕捉Android触控手机上的手指移动方向。如果用户向上/向下/向左/向右滑动手指，我想捕获此方向。我怎么能找到这个？感谢。

Answer 1

实现onTouchEvent（），并根据用户按下并抬起的位置计算dx和dy。您可以使用这些值来确定移动的方向。

float x1, x2, y1, y2, dx, dy;
String direction;
switch(event.getAction()) {
    case(MotionEvent.ACTION_DOWN):
        x1 = event.getX();
        y1 = event.getY();
        break;

    case(MotionEvent.ACTION_UP): {
        x2 = event.getX();
        y2 = event.getY();
        dx = x2-x1;
        dy = y2-y1;

        // Use dx and dy to determine the direction of the move
        if(Math.abs(dx) > Math.abs(dy)) {
            if(dx>0)
              direction = "right";
            else
              direction = "left";
        } else {
            if(dy>0)
              direction = "down";
            else
              direction = "up";
        }
    }
}

Answer 2

最好的办法是处理从View.OnTouchListener（）回调中获得的MotionEvent。运动事件会跟踪您当前如何通过其动作属性与View进行交互。

我想你可以通过检查MotionEvents的动作属性和动作事件发生位置的x / y值来计算某人滑动手指的方向。

switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            oldX= event.getX();
            oldY= event.getY();
            break;
        case MotionEvent.ACTION_MOVE:
            int newX = motionEvent.getX();
            int newY = motionEvent.getY();

            int deltaX = oldX - newX;
            int deltaY = oldY - newY;

            if(Math.abs(deltaY)>Math.abs(deltaX))
              //Motion in Y direction.
            else
              // Motion in X direction.
            break;
         }

MotionEvent对象上还有许多其他方法可供使用： http://developer.android.com/reference/android/view/MotionEvent.html

Answer 3

我认为最好使用VelocityTracker

这里是Developer Android

的修改示例

private var mVelocityTracker: VelocityTracker? = null

override fun onTouchEvent(event: MotionEvent): Boolean {

    when (event.actionMasked) {
        MotionEvent.ACTION_DOWN -> {
            // Reset the velocity tracker back to its initial state.
            mVelocityTracker?.clear()
            // If necessary retrieve a new VelocityTracker object to watch the
            // velocity of a motion.
            mVelocityTracker = mVelocityTracker ?: VelocityTracker.obtain()
            // Add a user's movement to the tracker.
            mVelocityTracker?.addMovement(event)
        }
        MotionEvent.ACTION_MOVE -> {
            mVelocityTracker?.run {
                val pointerId: Int = event.getPointerId(event.actionIndex)
                addMovement(event)
                // When you want to determine the velocity, call
                // computeCurrentVelocity(). Then call getXVelocity()
                // and getYVelocity() to retrieve the velocity for each pointer ID.
                computeCurrentVelocity(1000)

                val xVelocity = getXVelocity(pointerId)
                val yVelocity = getYVelocity(pointerId)

                if (abs(xVelocity) > abs(yVelocity))
                    if (xVelocity > 0)
                        // right
                    else
                        // left 
                else
                    if (yVelocity > 0)
                       // down
                    else
                       // up
            }
        }
        MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> {
            // Return a VelocityTracker object back to be re-used by others.
            mVelocityTracker?.recycle()
            mVelocityTracker = null
        }
    }
    return true
}

如何在Android手机中捕捉手指运动方向？

3 个答案: