背景
我想要创建一个RecyclerView，其中包含不同的视图类型，并具有拖放、单击和长按操作功能。
这与您在电话应用程序上所拥有的类似，您可以更改喜爱项目的顺序。 在电话应用程序上，当您长按一个项目时，上下文菜单会立即出现，如果继续拖动，则上下文菜单会消失。
然而，在这种情况下，我需要做相反的事情。长按后，如果用户短时间内没有拖动或者用户停止了长按而没有拖动，我们会在屏幕上显示一个对话框，并且我需要停止拖动过程。
问题
尽管我已经成功地处理了长按机制，并在这些特殊情况下显示了对话框，但我未能停止拖动。
这意味着，即使在对话框出现后，用户仍然可以继续触摸屏幕并继续拖动：
整个代码可在这里找到（没有长按行为的代码可在这里找到），以下是主要代码：
class MainActivity : AppCompatActivity() {
sealed class Item(val id: Long, val itemType: Int) {
class HeaderItem(id: Long) : Item(id, ITEM_TYPE_HEADER)
class NormalItem(id: Long, val data: Long) : Item(id, 1)
}
enum class ItemActionState {
IDLE, LONG_TOUCH_OR_SOMETHING_ELSE, DRAG, SWIPE, HANDLED_LONG_TOUCH
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setSupportActionBar(toolbar)
val items = ArrayList<Item>(100)
var itemDataCounter = 0L
items.add(Item.HeaderItem(0L))
for (i in 0 until 100) {
items.add(Item.NormalItem(itemDataCounter, itemDataCounter))
++itemDataCounter
}
val gridLayoutManager = recyclerView.layoutManager as GridLayoutManager
gridLayoutManager.spanSizeLookup = object : GridLayoutManager.SpanSizeLookup() {
override fun getSpanSize(position: Int): Int {
return when (recyclerView.adapter!!.getItemViewType(position)) {
ITEM_TYPE_HEADER -> gridLayoutManager.spanCount
ITEM_TYPE_NORMAL -> 1
else -> throw Exception("unknown item type")
}
}
}
recyclerView.adapter = object : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
init {
setHasStableIds(true)
}
override fun getItemViewType(position: Int): Int = items[position].itemType
override fun getItemId(position: Int): Long = items[position].id
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
val view = when (viewType) {
ITEM_TYPE_HEADER -> LayoutInflater.from(parent.context).inflate(R.layout.header_item, parent, false)
ITEM_TYPE_NORMAL -> LayoutInflater.from(parent.context).inflate(R.layout.grid_item, parent, false)
else -> throw Exception("unknown item type")
}
return object : RecyclerView.ViewHolder(view) {}
}
override fun getItemCount() = items.size
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
when (getItemViewType(position)) {
ITEM_TYPE_NORMAL -> {
val data = (items[position] as Item.NormalItem).data
holder.itemView.setBackgroundColor(when (data % 4L) {
0L -> 0xffff0000.toInt()
1L -> 0xffffff00.toInt()
2L -> 0xff00ff00.toInt()
else -> 0xff00ffff.toInt()
})
holder.itemView.textView.text = "item $data"
}
ITEM_TYPE_HEADER -> {
}
else -> throw Exception("unknown item type")
}
}
}
val itemTouchHelper = ItemTouchHelper(object : ItemTouchHelper.Callback() {
val touchSlop = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 1f, resources.displayMetrics)
// val touchSlop = ViewConfiguration.get(this@MainActivity).scaledTouchSlop
val longTouchTimeout = ViewConfiguration.getLongPressTimeout() * 2
var touchState: ItemActionState = ItemActionState.IDLE
var lastViewHolderPosHandled: Int? = null
val handler = Handler()
val longTouchRunnable = Runnable {
if (lastViewHolderPosHandled != null && touchState == ItemActionState.LONG_TOUCH_OR_SOMETHING_ELSE) {
// Log.d("AppLog", "timer timed out to trigger long touch")
onItemLongTouch(lastViewHolderPosHandled!!)
}
}
private fun onItemLongTouch(pos: Int) {
// Log.d("AppLog", "longTouchTimeout:$longTouchTimeout")
val item = items[pos] as Item.NormalItem
// Toast.makeText(this@MainActivity, "long touch on :$pos ", Toast.LENGTH_SHORT).show()
AlertDialog.Builder(this@MainActivity).setTitle("long touch").setMessage("long touch on pos: $pos - item ${item.data}").show()
touchState = ItemActionState.HANDLED_LONG_TOUCH
lastViewHolderPosHandled = null
handler.removeCallbacks(longTouchRunnable)
}
override fun onChildDrawOver(c: Canvas, recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder?, dX: Float, dY: Float, actionState: Int, isCurrentlyActive: Boolean) {
super.onChildDrawOver(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
// Log.d("AppLog", "onChildDrawOver $dX $dY pos:${viewHolder?.adapterPosition} actionState:$actionState isCurrentlyActive:$isCurrentlyActive")
if (touchState == ItemActionState.LONG_TOUCH_OR_SOMETHING_ELSE && (dX >= touchSlop || dY >= touchSlop)) {
lastViewHolderPosHandled = null
handler.removeCallbacks(longTouchRunnable)
touchState = if (actionState == ItemTouchHelper.ACTION_STATE_DRAG) ItemActionState.DRAG else ItemActionState.SWIPE
Log.d("AppLog", "decided it's not a long touch, but $touchState instead")
}
}
override fun onSelectedChanged(viewHolder: RecyclerView.ViewHolder?, actionState: Int) {
super.onSelectedChanged(viewHolder, actionState)
// Log.d("AppLog", "onSelectedChanged adapterPosition: ${viewHolder?.adapterPosition} actionState:$actionState")
when (actionState) {
ItemTouchHelper.ACTION_STATE_IDLE -> {
//user finished drag or long touch
if (touchState == ItemActionState.LONG_TOUCH_OR_SOMETHING_ELSE)
onItemLongTouch(lastViewHolderPosHandled!!)
touchState = ItemActionState.IDLE
handler.removeCallbacks(longTouchRunnable)
lastViewHolderPosHandled = null
}
ItemTouchHelper.ACTION_STATE_DRAG, ItemTouchHelper.ACTION_STATE_SWIPE -> {
if (touchState == ItemActionState.IDLE) {
lastViewHolderPosHandled = viewHolder!!.adapterPosition
// Log.d("AppLog", "setting timer to trigger long touch")
handler.removeCallbacks(longTouchRunnable)
//started as long touch, but could also be dragging or swiping ...
touchState = ItemActionState.LONG_TOUCH_OR_SOMETHING_ELSE
handler.postDelayed(longTouchRunnable, longTouchTimeout.toLong())
}
}
}
}
override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
// Log.d("AppLog", "onMove")
if (touchState == ItemActionState.LONG_TOUCH_OR_SOMETHING_ELSE) {
lastViewHolderPosHandled = null
handler.removeCallbacks(longTouchRunnable)
touchState = ItemActionState.DRAG
}
if (viewHolder.itemViewType != target.itemViewType)
return false
val fromPosition = viewHolder.adapterPosition
val toPosition = target.adapterPosition
// val item = items.removeAt(fromPosition)
// recyclerView.adapter!!.notifyItemRemoved(fromPosition)
// items.add(toPosition, item)
// recyclerView.adapter!!.notifyItemInserted(toPosition)
Collections.swap(items, fromPosition, toPosition)
recyclerView.adapter!!.notifyItemMoved(fromPosition, toPosition)
// recyclerView.adapter!!.notifyDataSetChanged()
return true
}
override fun isLongPressDragEnabled(): Boolean = true
override fun isItemViewSwipeEnabled(): Boolean = false
override fun getMovementFlags(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder): Int {
if (viewHolder.itemViewType == ITEM_TYPE_HEADER)
return makeMovementFlags(0, 0)
// Log.d("AppLog", "getMovementFlags")
val dragFlags = ItemTouchHelper.UP or ItemTouchHelper.DOWN or ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT
val swipeFlags = if (isItemViewSwipeEnabled) ItemTouchHelper.START or ItemTouchHelper.END else 0
return makeMovementFlags(dragFlags, swipeFlags)
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
if (touchState == ItemActionState.LONG_TOUCH_OR_SOMETHING_ELSE) {
lastViewHolderPosHandled = null
handler.removeCallbacks(longTouchRunnable)
touchState = ItemActionState.DRAG
}
val position = viewHolder.adapterPosition
items.removeAt(position)
recyclerView.adapter!!.notifyItemRemoved(position)
}
})
itemTouchHelper.attachToRecyclerView(recyclerView)
}
override fun onCreateOptionsMenu(menu: Menu): Boolean {
menuInflater.inflate(R.menu.menu_main, menu)
return true
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
var url: String? = null
when (item.itemId) {
R.id.menuItem_all_my_apps -> url = "https://play.google.com/store/apps/developer?id=AndroidDeveloperLB"
R.id.menuItem_all_my_repositories -> url = "https://github.com/AndroidDeveloperLB"
R.id.menuItem_current_repository_website -> url = "https://github.com/AndroidDeveloperLB/RecyclerViewDragAndDropTest"
}
if (url == null)
return true
val intent = Intent(Intent.ACTION_VIEW, Uri.parse(url))
@Suppress("DEPRECATION")
intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY or Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET)
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_MULTIPLE_TASK)
startActivity(intent)
return true
}
companion object {
const val ITEM_TYPE_HEADER = 0
const val ITEM_TYPE_NORMAL = 1
}
}
我尝试过的
我尝试查看RecyclerView和ItemTouchHelper的所有文档，并在这里和互联网上寻找类似的问题。
我无法找到任何方法来告诉拖动机制：“我已经完成拖动，取消拖动”。
问题
如何取消由ItemTouchHelper启动和维护的拖动？
getMovementFlags方法来覆盖状态。 在传递给该方法的viewHolder参数中，您可以使用viewHolder.getAdapterPostition()获取位置。 - Rahul KhuranaitemTouchHelper.attachToRecyclerView(null);可以取消触摸。 - Rahul Khurana