WPF C# - DataGrid select 用户按键上的项目

Question

我将此功能设为 select 用户按键时 DataGrid 上的项目。如果用户密钥是 "A"，它将 select 用户名以字母 "A" 开头的第一项。如果用户密钥再次为 "A"，它将 select 用户名以字母 "A" 开头的下一个项目，依此类推。该功能效果很好，但我想要的是当没有更多用户名以 "A" 开头的项目重新开始时（select 第一项），它目前保留在用户名开头的最后一个项目上字母 "A".

private static Key lastKey;
private static int lastFoundIndex = 0;

public static void AccountsDataGrid_SearchByKey(object sender, KeyEventArgs e)
{
    DataGrid dataGrid = sender as DataGrid;

    if ((dataGrid.Items.Count == 0) && !(e.Key >= Key.A && e.Key <= Key.Z))
    {
        return;
    }

    if ((lastKey != e.Key) || (lastFoundIndex == dataGrid.Items.Count - 1))
    {
        lastFoundIndex = 0;
    }

    for (int i = lastFoundIndex; i < dataGrid.Items.Count; i++)
    {
        if (dataGrid.SelectedIndex == i)
        {
            continue;
        }

        Account account = dataGrid.Items[i] as Account;

        if (account.Username.StartsWith(e.Key.ToString(), true, CultureInfo.CurrentCulture))
        {
            dataGrid.ScrollIntoView(account);
            dataGrid.SelectedItem = account;

            lastFoundIndex = i;

            break;
        }
    }

    lastKey = e.Key;
}

更新（含解决方案）：

受 Danielle 想法的启发，我修改了如下代码，效果非常好。

private static Key lastKey;
private static int lastFoundIndex = 0;

public static void AccountsDataGrid_SearchByKey(object sender, KeyEventArgs e)
{
    DataGrid dataGrid = sender as DataGrid;

    if ((dataGrid.Items.Count == 0) && !(e.Key >= Key.A && e.Key <= Key.Z))
    {
        return;
    }

    if ((lastKey != e.Key) || (lastFoundIndex == dataGrid.Items.Count - 1))
    {
        lastFoundIndex = 0;
    }

    Func<object, bool> itemCompareMethod = (item) =>
    {
        Account account = item as Account;

        if (account.Username.StartsWith(e.Key.ToString(), true, CultureInfo.CurrentCulture))
        {
            return true;
        }

        return false;
    };

    lastFoundIndex = FindDataGridRecordWithinRange(dataGrid, lastFoundIndex, dataGrid.Items.Count, itemCompareMethod);

    if (lastFoundIndex == -1)
    {
        lastFoundIndex = FindDataGridRecordWithinRange(dataGrid, 0, dataGrid.Items.Count, itemCompareMethod);
    }

    if (lastFoundIndex != -1)
    {
        dataGrid.ScrollIntoView(dataGrid.Items[lastFoundIndex]);
        dataGrid.SelectedIndex = lastFoundIndex;
    }

    if (lastFoundIndex == -1)
    {
        lastFoundIndex = 0;
        dataGrid.SelectedItem = null;
    }

    lastKey = e.Key;
}

private static int FindDataGridRecordWithinRange(DataGrid dataGrid, int min, int max, Func<object, bool> itemCompareMethod)
{
    for (int i = min; i < max; i++)
    {
        if (dataGrid.SelectedIndex == i)
        {
            continue;
        }

        if (itemCompareMethod(dataGrid.Items[i]))
        {
            return i;
        }
    }

    return -1;
}

Answer 1

您的代码表示要从头开始重新搜索，lastFoundIndex 应等于 dataGrid.Items.Count - 1（假设再次按下相同的键）。但是您最后找到的 Account 可能不在 Items 集合的末尾，因此在按下前一个键时 lastFoundIndex 未设置为 dataGrid.Items.Count - 1。这种情况下你重新开始的条件不满足。

尝试像这样更改最后发现的检查和 "for" 循环：

bool found = false; 
bool lastFound = true;

if (lastKey != e.Key || lastFound)
{
    lastFoundIndex = 0;
}

for (int i = lastFoundIndex; i < dataGrid.Items.Count; i++)
{
    if (dataGrid.SelectedIndex == i)
    {
        continue;
    }

    Account account = dataGrid.Items[i] as Account;

    if (account.Username.StartsWith(e.Key.ToString(), true, CultureInfo.CurrentCulture))
    {
        if (!found)
        {
            dataGrid.ScrollIntoView(account);
            dataGrid.SelectedItem = account;

            lastFoundIndex = i;
            found = true;
        }
        else
        {
            lastFound = false;
            break;
        }
    }
}

基本上它会尝试再找到一个项目，看看它是否是最后一场比赛。

Answer 2

您可以将 for 循环提取到一个单独的方法中，以确定是否找到了另一项。

public int FindRecordWithinRange(DataGrid dataGrid, int min, int max)
{
    for (int i = min; i < max; i++)
    {
        if (dataGrid.SelectedIndex == i)
            continue;

        Account account = dataGrid.Items[i] as Account;

        if (account.Username.StartsWith(e.Key.ToString(), true, CultureInfo.CurrentCulture))
        {
            dataGrid.ScrollIntoView(account);
            dataGrid.SelectedItem = account;

            return i;
        }
    }

    return -1;
}

然后使用类似这样的方式调用它：

lastFoundIndex = FindRecordWithinRange(dataGrid, lastFoundIndex, dataGrid.Items.Count);
if (lastFoundIndex == -1)
    lastFoundIndex = FindRecordWithinRange(dataGrid, 0, dataGrid.Items.Count);
if (lastFoundIndex == -1)
    dataGrid.SelectedItem = null;

这基本上会尝试从头开始搜索列表，并且还会通过清除选择来处理未找到任何项目的情况。在这种情况下，您可能还想滚动到开头，此时的处理取决于您要做什么。

你可能想在这里做的另一件事是提取你的 ScrollIntoView 和选择逻辑，并在索引确定后处理它。

Answer 3

如果我像下面这样更改我的功能，它将在字母 "A" 的最后一项停留 2 次，然后再转到字母 "A" 的第一项（假设用户键仍然是 "A").

    private static Key lastKey;
    private static int lastFoundIndex = 0;

    public static void AccountsDataGrid_SearchByKey(object sender, KeyEventArgs e)
    {
        DataGrid dataGrid = sender as DataGrid;

        if ((dataGrid.Items.Count == 0) && !(e.Key >= Key.A && e.Key <= Key.Z))
        {
            return;
        }

        if ((lastKey != e.Key) || (lastFoundIndex == dataGrid.Items.Count - 1))
        {
            lastFoundIndex = 0;
        }

        for (int i = lastFoundIndex; i < dataGrid.Items.Count; i++)
        {
            if ((lastFoundIndex > 0) && (lastFoundIndex == i))
            {
                lastFoundIndex = 0;
            }

            if (dataGrid.SelectedIndex == i)
            {
                continue;
            }

            Account account = dataGrid.Items[i] as Account;

            if (account.Username.StartsWith(e.Key.ToString(), true, CultureInfo.CurrentCulture))
            {
                dataGrid.ScrollIntoView(account);
                dataGrid.SelectedItem = account;

                lastFoundIndex = i;

                break;
            }
        }

        lastKey = e.Key;
    }

Answer 4

您最终采用的解决方案过于复杂，并且会检查不需要检查的行。也不需要维护状态的两个静态变量。试试这个：

    public void MainGrid_SearchByKey(object sender, KeyEventArgs e)
    {
        DataGrid dataGrid = sender as DataGrid;
        if (dataGrid.Items.Count == 0 || e.Key < Key.A || e.Key > Key.Z)
        {
            return;
        }

        Func<object, bool> doesItemStartWithChar = (item) =>
        {
            Account account = item as Account;
            return account.Username.StartsWith(e.Key.ToString(), true, CultureInfo.InvariantCulture);
        };

        int currentIndex = dataGrid.SelectedIndex;
        int foundIndex = currentIndex;

        // Search in following rows
        foundIndex = FindMatchingItemInRange(dataGrid, currentIndex, dataGrid.Items.Count - 1, doesItemStartWithChar);

        // If not found, search again in the previous rows
        if (foundIndex == -1)
        {
            foundIndex = FindMatchingItemInRange(dataGrid, 0, currentIndex - 1, doesItemStartWithChar);
        }

        if (foundIndex > -1) // Found
        {
            dataGrid.ScrollIntoView(dataGrid.Items[foundIndex]);
            dataGrid.SelectedIndex = foundIndex;
        }
    }

    private static int FindMatchingItemInRange(DataGrid dataGrid, int min, int max, Func<object, bool> doesItemStartWithChar)
    {
        for (int i = min; i <= max; i++)
        {
            if (dataGrid.SelectedIndex == i) // Skip the current selection
            {
                continue;
            }

            if (doesItemStartWithChar(dataGrid.Items[i])) // If current item matches the string, return index
            {
                return i;
            }
        }

        return -1;
    }

关于您的评论，只需添加此检查：

        if (Keyboard.Modifiers.HasFlag(ModifierKeys.Control))
        {
            return;
        }

WPF C# - DataGrid select 用户按键上的项目

WPF C# - DataGrid select item on user keypress

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