切换视图模式后，ListView控件不显示图片 [英] ListView does not show images after switching view mode

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问题描述

当我加入项目（S）的的ListView 在任何其他比 LargeIcon 视图模式下，的ListView 停止显示来自 LargeImageList 当它切换回 LargeIcon 。这种情况一直持续到新的项目加入到 LargeIcon 模式的的ListView 。

When I add item(s) to the ListView in any other than LargeIcon view mode, the ListView stops showing the images from LargeImageList when it is switched back to LargeIcon. This situation lasts until new item is added to the ListView in the LargeIcon mode.

所以，按以下顺序说明了这个问题：

So the following sequence illustrates the problem:

  1. 创建的ListView ，添加列，设置查看到详细信息
  2. 创建的ImageList ，设置 IMAGESIZE ，将其分配给 ListView.LargeImageList
  3. 创建新的的ListViewItem ，设置其 ImageKey
  4. 创建新的形象，它与给定的密钥添加到的ImageList
  5. 添加的ListViewItem 到的ListView
  6. 切换的ListView 模式 LargeIcon
    • 无图像显示
  1. create ListView, add column, set View to Details
  2. create ImageList, set ImageSize, assign it to ListView.LargeImageList
  3. create new ListViewItem, set its ImageKey
  4. create new image, add it to the ImageList with given key
  5. add the ListViewItem to the ListView
  6. switch the ListView mode to LargeIcon
    • no images are shown
  • 所有图像都显示为预期

有什么意思，我仍然失踪？

我曾尝试以下操作：

  • 无效的ListView
  • 重新分配 LargeImageList 前/添加项目之后（甚至通过空）
  • Invalidate the ListView
  • Re-assign the LargeImageList before/after adding the item (even through null)

测试code对于那些谁喜欢话多的：

The test code for those who like it more than words:

public partial class Form1 : Form
{
    int       counter = 0;
    ImageList iList   = new ImageList();

    private string GetNewKey()
    {
        return counter++.ToString();
    }

    private Image GetNewImage(Size size)
    {
        var bmp = new Bitmap(size.Width, size.Height);

        using (var gra = Graphics.FromImage(bmp))
        {
            var rnd = new Random();

            var lines = rnd.Next(1000);

            for (int l = 0; l < lines; ++l)
            {
                var pen = new Pen(Color.FromArgb(rnd.Next(256), rnd.Next(256), rnd.Next(256)));
                var p1  = new Point(rnd.Next(size.Width), rnd.Next(size.Height)); 
                var p2  = new Point(rnd.Next(size.Width), rnd.Next(size.Height));
                gra.DrawLine(pen, p1, p2);
            }
        }

        return bmp;
    }

    public Form1()
    {
        InitializeComponent();

        iList.ImageSize         = new Size(100, 100);
        listView.LargeImageList = iList;
        listView.Columns.Add("name");
    }

    private void buttonAdd_Click(object sender, EventArgs e)
    {
        var key = GetNewKey();
        var lvi = new ListViewItem()
        {
            Name     = key,
            Text     = "blabla",
            ImageKey = key,
        };

        iList.Images.Add(key, GetNewImage(new Size(100, 100)));
        listView.Items.Add(lvi);
    }

    private void buttonClear_Click(object sender, EventArgs e)
    {
        listView.Items.Clear();
    }

    private void buttonLarge_Click(object sender, EventArgs e)
    {
        listView.View = View.LargeIcon;
    }

    private void buttonDetails_Click(object sender, EventArgs e)
    {
        listView.View = View.Details;
    }
}

编辑：

对于任何人谁也遭受了同样的问题。一些实验后，至少有愚蠢的可怜人的解决方法：

For anyone who would suffer the same problem. After some experiments, there is at least stupid poor man's workaround:

修改的ImageList 的的ListView 不知何故检测其变化并重新载入图片为 LargeIcon 模式。这些问题是如何它检测到的变化和为什么它忽略的ImageList 模式改变后...

Modify the ImageList, the ListView somehow detects its change and reloads the images for LargeIcon mode. The questions are how it detects the change and why does it ignore the ImageList after mode change...

    private void FixIt()
    {
        // Trigger a reload of the ListView.LargeImageList
        if (listView.View == View.LargeIcon)
        {
            var key = "Dummy image to be deleted right after its insertion...";
            iList.Images.Add(key, new Bitmap(1, 1));
            iList.Images.RemoveByKey(key);            
        }
    }

编辑＃2： 我还发现了其他一些有趣的功能的ListView 和相关的组件有。您可能要检查他们的答案<一href="http://stackoverflow.com/questions/4097912/why-does-subitems-clear-also-delete-the-name-attribute">question 4097912 和<一href="http://stackoverflow.com/questions/23059678/imagelist-strange-behaviour-ater-changing-imagesize">question 23059678

EDIT #2: I have also discovered some other funny features the ListView and associated components have. You might want to check them in answers of question 4097912 and question 23059678

推荐答案

解决你的问题

您可以通过期运用避免这种的ImageIndex 而不是 ImageKey 来连接你的的ListView 与的ImageList 。因此，在你的 buttonAdd_Click 事件中使用：

You could avoid this by useing ImageIndex instead of ImageKey to connect your ListView with the ImageList. So in your buttonAdd_Click event use:

  var lvi = new ListViewItem()
        {
            Name     = key,
            Text     = "blabla",
            //ImageKey = key,
            //Use ImageIndex and don't set both
            ImageIndex= Convert.ToInt32(key) //you could just use count++ 
        };

这背后的问题，究其原因：

这背后的原因是我也不清楚，但我认为这可能是一个错误，从详细信息更改为 LargeIcon ，它只是在默认检查的ImageIndex 如果设置 ImageKey 的的ImageIndex 将被设置为 1 。或者可能是这是由设计，我不知道（见下文 ImageKey 部分），因为你没有一个 SmallImageList ，所以改为 LargeIcon 视图，的ImageIndex 是空或 1 和 ImageKey 被忽略。

The reason behind this is not clear to me, but I assume this may be a bug that when changing from Details to LargeIcon, it only checks ImageIndex in default and if you set ImageKey the ImageIndex will be set to -1. Or may be this is by design, I don't know (see ImageKey section below), since you don't have a SmallImageList, so when changing to LargeIcon view, ImageIndex is null or -1 and the ImageKey is ignored.

关于<一个href="http://msdn.microsoft.com/en-us/library/system.windows.forms.listviewitem.imageindex%28v=vs.110%29.aspx"相对=nofollow> ListViewItem.ImageIndex物业

About ListViewItem.ImageIndex Property

在ImageKey和图像索引的属性是相互排斥的，这意味着如果已设置，另一个被忽略。此外，如果你设置ImageKey属性，ImageIndex属性被自动设置为-1。另外，如果设置了ImageIndex属性，该ImageKey被自动设置为空字符串（）。

The ImageKey and ImageIndex properties are mutually exclusive, meaning if one is set, the other is ignored. Furthermore, if you set the ImageKey property, the ImageIndex property is automatically set to -1. Alternatively, if you set the ImageIndex property, the ImageKey is automatically set to an empty string ("").

关于<一个href="http://msdn.microsoft.com/en-us/library/system.windows.forms.listviewitem.imagekey%28v=vs.110%29.aspx"相对=nofollow> ListViewItem.ImageKey物业

About ListViewItem.ImageKey Property

如果您正在使用多个图像列表，为小型和大型图标视图，具有ListView控件，你应该把大大小小的版本的形象在他们各自的图像列表相同的索引位置。的的当视图之间切换时，图像的一个列表中的索引位置被用来定位图像中的其他列表，而不管指定的密钥值的的

If you are using multiple image lists, for small and large icon view, with a ListView control, you should place small and large versions of the image at the same index location in their respective image lists. When switching between views, the index location of the image in one list is used to locate the image in the other list, regardless of the key value specified.

这能以某种方式进行验证：

And this can somehow be verified:

  • 在使用现有的code（使用 ImageKey ）
  • 设置的ImageIndex 任何项的的ListView 在 buttonLarge_Click 事件处理程序会告诉你该项目的形象。
  • 设置 ImageKey 任何项目在 buttonLarge_Click 事件处理程序将不会显示，纺织机械展览会的形象。
  • using your existing code (use ImageKey)
  • set ImageIndex for any Item in your listView within the buttonLarge_Click event handler will show you that item's image.
  • set ImageKey for any Item within the buttonLarge_Click event handler will not show that itme's image.

例如：

 private void buttonLarge_Click(object sender, EventArgs e)
        {
            listView.View = View.LargeIcon;
            //Set ImageIndex of Item 0 you could see its Icon.
            listView.Items[0].ImageIndex= 0 ;

            //set ImageKey will change nothing 
            //listView.Items[0].ImageKey= "0" ; 
        }

这篇关于切换视图模式后，ListView控件不显示图片的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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