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我有以下代碼來偵聽從WPF ListView啓動拖放事件。 這個想法是,一個鼠標向下的事件後,將鼠標移動。一旦鼠標移動超過最小距離,拖放操作將開始。使用無效擴展檢測MouseDown和MouseMove事件
var mouseDowns = Observable.FromEventPattern<MouseEventArgs>(this, "PreviewMouseDown");
var mouseMoves = Observable.FromEventPattern<MouseEventArgs>(this, "MouseMove").
Where(
x =>
x.EventArgs.LeftButton == MouseButtonState.Pressed ||
x.EventArgs.RightButton == MouseButtonState.Pressed);
var drag = from mouseDown in mouseDowns
from mouseMove in mouseMoves
let initialPosition = mouseDown.EventArgs.GetPosition(null)
let currentPosition = mouseMove.EventArgs.GetPosition(null)
let mouseDifference = initialPosition - currentPosition
//where
// (Math.Abs(mouseDifference.X) > MinimumDragDistance ||
// Math.Abs(mouseDifference.Y) > MinimumDragDistance)
select mouseDifference;
dragSubscription = drag.Subscribe(_ =>
{
Debug.WriteLine(string.Format("x: {0} y: {1}", _.X, _.Y));
var dataObject = GetDataObject();
DragDrop.DoDragDrop(this, dataObject, DragDropEffects.Move);
});
的問題是,在LINQ的,只要符合條件的PreviewMouseDown事件觸發,只有一個mouseMove事件被捕獲,這意味着,當我在列表中包括了where
說法,mouseDifference始終爲0,不符合條件。
有沒有辦法允許多鼠標移動事件發生,直到一個匹配條件發生?