Android：以编程方式创建滑动手势事件

Question

我一直在尝试在Google上找到针对此特定案例的答案，但令人惊讶的是在任何地方都找不到它（只是关于检测而不是创建，滑动的答案）。我实际上想在屏幕上从右向左“模拟”滑动（无关紧要，但最好是从右边缘向左滑动）。我尝试过类似的方法，但得到了NPE：

final float viewWidth = view.getWidth();
    TouchUtils.drag(null,viewWidth,1f,0f,0f,1);

原因？我需要在没有实际引用页面位置的无限viewpager中强制滑动到下一页（所以我不能只使用setCurrentItem）。

有任何想法吗？

Answer 1

正如已经说过的TouchUtils.drag用途Instrumentation，只能用于androidTest。我编写了不需要的扩展函数Instrumentation，因此它们可以在发布版本中使用：

fun ViewGroup.performSwipeToLeft(target: View) {
    this.performSwipe(target, distanceX = -this.width * .5f, distanceY = 0f)
}
fun ViewGroup.performSwipeToRight(target: View) {
    this.performSwipe(target, distanceX = +this.width * .5f, distanceY = 0f)
}
fun ViewGroup.performSwipeToTop(target: View) {
    this.performSwipe(target, distanceX = 0f, distanceY = -this.height * .5f)
}
fun ViewGroup.performSwipeToBottom(target: View) {
    this.performSwipe(target, distanceX = 0f, distanceY = +this.width * .5f)
}

fun ViewGroup.performSwipe(target: View, distanceX: Float, distanceY: Float) {
    val parentCoords = intArrayOf(0, 0)
    this.getLocationInWindow(parentCoords)

    val childCoords = intArrayOf(0, 0)
    target.getLocationInWindow(childCoords)

    val initGlobalX = childCoords[0].toFloat() + 1f
    val initGlobalY = childCoords[1].toFloat() + 1f

    val initLocalX = (childCoords[0] - parentCoords[0]).toFloat() + 1f
    val initLocalY = (childCoords[1] - parentCoords[1]).toFloat() + 1f

    val downTime = SystemClock.uptimeMillis()
    var eventTime = SystemClock.uptimeMillis()

    this.dispatchTouchEvent(
        MotionEvent.obtain(
            downTime,
            eventTime,
            MotionEvent.ACTION_DOWN,
            initGlobalX,
            initGlobalY,
            0
        ).apply {
            setLocation(initLocalX, initLocalY)
            source = InputDevice.SOURCE_TOUCHSCREEN
        }
    )

    val steps = 20
    var i = 0
    while (i in 0..steps) {
        val globalX = initGlobalX + i * distanceX / steps
        val globalY = initGlobalY + i * distanceY / steps
        val localX = initLocalX + i * distanceX / steps
        val localY = initLocalY + i * distanceY / steps
        if (globalX <= 10f || globalY <= 10f) {
            break
        }
        this.dispatchTouchEvent(
            MotionEvent.obtain(
                downTime,
                ++eventTime,
                MotionEvent.ACTION_MOVE,
                globalX,
                globalY,
                0
            ).apply {
                setLocation(localX, localY)
                source = InputDevice.SOURCE_TOUCHSCREEN
            }
        )
        i++
    }

    this.dispatchTouchEvent(
        MotionEvent.obtain(
            downTime,
            ++eventTime,
            MotionEvent.ACTION_UP,
            initGlobalX + i * distanceX,
            initGlobalY + i * distanceY,
            0
        ).apply {
            setLocation(initLocalX + i * distanceX, initLocalY + i * distanceY)
            source = InputDevice.SOURCE_TOUCHSCREEN
        }
    )
}

要使用它，您需要将当前页面内容作为参数传递，并将 viewPager 作为此函数的接收者：

val viewPager = ...
viewPager.performSwipeToLeft(viewPager.getChildAt(viewPager.currentItem))