一次只能检查一个ListViewItem [英] Check only one ListViewItem at time

问题描述

我正在使用Compact Framework开发智能设备项目。

我有一个 ListView 可以查看 ListViewItem s：属性 CheckBoxes 是true。我只需要检查一个 ListViewItem ，所以我订阅了 ItemCheck 事件：

  //我需要知道最后一个项目
 private ListViewItem lastItemChecked; 
 
 private void listView_ItemCheck（object sender，ItemCheckEventArgs e）
 {
 if（lastItemChecked！= null&& lastItemChecked.Checked）
 {
 / *我需要执行以下操作来防止无限递归：
即订阅然后取消订阅ItemCheck事件。 * / 
 listView.ItemCheck  -  = listView_ItemCheck; 
 lastItemChecked.Checked = false; 
 listView.ItemCheck + = listView_ItemCheck; 
} 
 
 lastItemChecked = listView.Items [e.Index]; 
} 
  

有没有更好的方法来阻止无限递归，因此有$ code>堆栈溢出？

解决方案

嗯，我认为可能比玩杂耍EventHandler正在检查lastItemCheck是否是EventArgs中的当前项。像这样：

  //我需要知道最后一个项目
 private ListViewItem lastItemChecked; 
 
 private void listView_ItemCheck（object sender，ItemCheckEventArgs e）
 {
 //如果我们将lastItem设置为checked，并且它不同于
 // item than如果（lastItemChecked！= null&& lastItemChecked.Checked 
&& lastItemChecked！= listView.Items [e.Index]）
，则取消选中该事件
 {
 //取消选中最后一个项目并存储新的
 lastItemChecked.Checked = false; 
} 
 
 //存储当前项
 lastItemChecked = listView.Items [e.Index]; 
} 
  

我认为你会同意，重新分配EventHandlers有点比简单检查存储对象的引用更糟糕。

I'm developing a smart device project using the Compact Framework.

I have a ListView with several checkable ListViewItems: the property CheckBoxes is true. I need to check only one ListViewItem at time, so I subscribed the ItemCheck event:

// I need to know the last item checked
private ListViewItem lastItemChecked;

private void listView_ItemCheck(object sender, ItemCheckEventArgs e)
{
    if (lastItemChecked != null && lastItemChecked.Checked)
    {
        /* I need to do the following to prevent infinite recursion:
        i.e. subscribe and then unsubscribe the ItemCheck event. */
        listView.ItemCheck -= listView_ItemCheck;
        lastItemChecked.Checked = false;
        listView.ItemCheck += listView_ItemCheck;
    }

    lastItemChecked = listView.Items[e.Index];
}

Is there a better way to prevent the infinite recursion and thus the Stack Overflow?

解决方案

Well, I think what might be better than juggling with the EventHandlers is checking if the lastItemCheck is a current item from the EventArgs. Like this:

// I need to know the last item checked
private ListViewItem lastItemChecked;

private void listView_ItemCheck(object sender, ItemCheckEventArgs e)
{
    // if we have the lastItem set as checked, and it is different
    // item than the one that fired the event, uncheck it
    if (lastItemChecked != null && lastItemChecked.Checked
        && lastItemChecked != listView.Items[e.Index] )
    {
        // uncheck the last item and store the new one
        lastItemChecked.Checked = false;
    }

    // store current item
    lastItemChecked = listView.Items[e.Index];
}

I think that you'll agree, that re-assigning EventHandlers is a bit worse than simply checking the reference of the stored object.

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