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[英]Why is the ValueChanged event not triggered on a NumericUpDown Control When the Value is Changed Manually?
[英]NumericUpDown Control should fire ValueChanged Event only on scroll finished
我有一个numericUpDown控件(Windows窗体)。
我想听ValueChanged
事件。
我在属性中设置它,它的工作原理。
但:
我希望我可以“向上或向下滚动”。 (如果我把它做得更久会更快)
当我完成“滚动”时,我希望事件xyz现在被激活而不是在滚动期间。
我怎样才能做到这一点?
尝试使用mouseup事件。 当你用手指离开鼠标左键时会触发它,所以理论上它应该可以解决你的问题。
[詹姆斯编辑]在你的表格上试试这个控件。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace Example.CustomControl
{
/// <summary>
/// Provides an extra event for the numericUpDown control that fires after the value stops scrolling.
/// </summary>
public class NumericDelayedChange : NumericUpDown
{
/// <summary>
/// Flag that the value has actually changed.
/// </summary>
/// <devdoc>
/// Just in case the control was clicked somewhere other than the up/down buttons.
/// </devdoc>
private bool valueHasChanged = false;
/// <summary>
/// Fires when the value has stopped being scrolled.
/// </summary>
public event EventHandler OnAfterScollValueChanged;
/// <summary>
/// Captures that value as having changed.
/// </summary>
/// <param name="e"></param>
protected override void OnValueChanged(EventArgs e)
{
valueHasChanged = true;
base.OnValueChanged(e);
}
/// <summary>
/// Captures the mouse up event to identify scrolling stopped when used in combination with the value changed flag.
/// </summary>
/// <param name="mevent"></param>
protected override void OnMouseUp(MouseEventArgs mevent)
{
base.OnMouseUp(mevent);
if (mevent.Button == System.Windows.Forms.MouseButtons.Left)
{
PerformOnAfterScollValueChanged();
}
}
/// <summary>
/// Captures the key up/down events to identify scrolling stopped when used in combination with the value changed flag.
/// </summary>
/// <param name="mevent"></param>
protected override void OnKeyUp(KeyEventArgs e)
{
if (e.KeyCode == Keys.Up || e.KeyCode == Keys.Down)
{
PerformOnAfterScollValueChanged();
}
base.OnKeyUp(e);
}
/// <summary>
/// Checks the value changed flag and fires the OnAfterScollValueChanged event.
/// </summary>
private void PerformOnAfterScollValueChanged()
{
if (valueHasChanged)
{
valueHasChanged = false;
if (OnAfterScollValueChanged != null) { OnAfterScollValueChanged(this, new EventArgs()); }
}
}
}
}
你需要定义I'm done with the scroll
什么。 这可能是从滚动按钮移除鼠标,或从最后一次点击后经过一定时间。 在任何情况下,我认为你不能导致事件不运行,但你可以在事件处理程序中做一些检查。 例如:
private DateTime? lastClickTime;
public void MyUpDown_ValueChanged(object sender, EventArgs e)
{
if (lastClickTime != null && DateTime.Now.Subtract(lastClickTime.Value).Seconds > someInterval)
{
// Do the work
}
lastClickTime = DateTime.Now
}
但是,正如我所说,你首先要确定I'm done
。 这段代码并不完美。
这是解决问题的直接方法:只需检查是否使用Control.MouseButtons
按下鼠标按钮,如下所示:
private void numericUpDown1_ValueChanged(object sender, EventArgs e)
{
//don't update until done scrolling
if (Control.MouseButtons == MouseButtons.None)
{
// Do the work
}
}
这是我解决这个问题的方法:
任务检查“valueIsChanging”标志。 此标志由ValueChanged事件设置。 通过ValueChanged事件将此标志设置为True后,while循环完成并执行您的代码。
Task waitForValueSettleTask;
volatile bool valueIsChanging; // marked volaltile since it is access by multiple threads (the GUI thread, and the task)
private void numericUpDown_ValueChanged(object sender, EventArgs e)
{
valueIsChanging = true;
if (waitForValueSettleTask == null || waitForValueSettleTask != null &&
(waitForValueSettleTask.IsCanceled || waitForValueSettleTask.IsCompleted || waitForValueSettleTask.IsFaulted))
{
waitForValueSettleTask = Task.Run(() =>
{
while (valueIsChanging)
{
valueIsChanging = false;
Thread.Sleep(1000); // Set this to whatever settling time you'd like
}
// Your code goes here
});
}
}
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