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[英]Android: Recyclerview with ItemTouchHelper.Callback flickering on lower items in list
[英]RecyclerView ItemTouchHelper.Callback: Dragging swap condition
我想以这样一种方式实现卡片的拖动,当我拖动的卡片没有完全重叠元素时,卡片的重新排列开始,但只有 50%。
看一个例子:
现在,要让右卡向左移动,我需要将它与我拖动的卡完全重叠。
我尝试从 ItemTouchHelper.Callback 覆盖此方法:
public float getMoveThreshold(@NonNull ViewHolder viewHolder) {
return .5f;
}
但这没有帮助。
那么我怎样才能使交换发生在 50% 而不是 100% 重叠?
经过多次尝试,我自己找到了解决方案:
您需要覆盖 ItemTouchHelper.Callback 中的 chooseDropTarget 方法。
我是这样做的:
// x ≥ 0.5 (if less than 0.5, it will shake due to constant overlap)
val DRAG_THRESHOLD_PERSENT = 0.5
override fun chooseDropTarget(
selected: ViewHolder,
targets: MutableList<ViewHolder>,
curX: Int, curY: Int
): ViewHolder? {
val verticalOffset = (selected.itemView.height * DRAG_THRESHOLD_PERSENT).toInt()
val horizontalOffset = (selected.itemView.width * DRAG_THRESHOLD_PERSENT).toInt()
val left = curX - horizontalOffset
val right = curX + selected.itemView.width + horizontalOffset
val top = curY - verticalOffset
val bottom = curY + selected.itemView.height + verticalOffset
var winner: ViewHolder? = null
var winnerScore = -1
val dx = curX - selected.itemView.left
val dy = curY - selected.itemView.top
val targetsSize = targets.size
for (i in 0 until targetsSize) {
val target = targets[i]
if (dx > 0) {
val diff = target.itemView.right - right
if (diff < 0 && target.itemView.right > selected.itemView.right) {
val score = abs(diff)
if (score > winnerScore) {
winnerScore = score
winner = target
}
}
}
if (dx < 0) {
val diff = target.itemView.left - left
if (diff > 0 && target.itemView.left < selected.itemView.left) {
val score = abs(diff)
if (score > winnerScore) {
winnerScore = score
winner = target
}
}
}
if (dy < 0) {
val diff = target.itemView.top - top
if (diff > 0 && target.itemView.top < selected.itemView.top) {
val score = abs(diff)
if (score > winnerScore) {
winnerScore = score
winner = target
}
}
}
if (dy > 0) {
val diff = target.itemView.bottom - bottom
if (diff < 0 && target.itemView.bottom > selected.itemView.bottom) {
val score = abs(diff)
if (score > winnerScore) {
winnerScore = score
winner = target
}
}
}
}
return winner
}
这个怎么运作:
我正在使用因子和宽度/高度计算所选视图的偏移量。 之后,我创建新边框(左、右、上、下),为所选视图的边框添加偏移量,然后在方法中使用它们而不是原始边框
重要的:
我没有解决方案,但我仍然想分享我的观察。 看起来您从 getMoveThreshold() 方法返回的任何低于 1 的值都不会改变默认行为,但是实际上高于 1 的值会改变。
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