Question

我有两个按钮，一个是向后，另一个是向前。两个按钮都会逐个显示文本块中的“收藏”项。前进按钮正常工作，但后退按钮始终跳过收藏列表中的第一项。

示例 - 我在收藏夹列表中有5个项目。如果我在第二项，如果我按向后按钮然后它直接跳转到最后一项并跳过收藏列表中的第一项

XAML

 <Button Name="BackwardButton" FontFamily="Segoe MDL2 Assets" Content="&#xE26C;" />
 <Button Name="ForwardButton" FontFamily="Segoe MDL2 Assets" Content="&#xE26B;" />
 <TextBlock Name="DisplayTextBlock" />

C＃

private int _displayedFavoriteIndex = -1;

private void BackwardButton_Tapped(object sender, TappedRoutedEventArgs e)
{
    if (FavoriteListBox.Items.Count > 1)
    {
        //move to the previous item
        _displayedFavoriteIndex--;
        if (_displayedFavoriteIndex <= 0)
        {
            //we have reached the end of the list
            _displayedFavoriteIndex = listobj.Count - 1;
        }
        //show the item            
        DisplayTextBlock.Text = listobj[ _displayedFavoriteIndex ].AnswerName;
    }
}

private void ForwardButton_Tapped(object sender, TappedRoutedEventArgs e)
{
    if (FavoriteListBox.Items.Count > 1)
    {
        //move to the next item
        _displayedFavoriteIndex++;
        if (_displayedFavoriteIndex >= listobj.Count)
        {
            //we have reached the end of the list
            _displayedFavoriteIndex = 0;
        }
        //show the item            
        DisplayTextBlock.Text = listobj[ _displayedFavoriteIndex ].AnswerName;
    }
}

Answer 1

在检查到达列表的开头时，请换取position <= 0。这包括第一项的情况，其中position == 0。

将条件更改为position < 0，它将按预期工作。

Answer 2

如果是条件，你需要更新你，它应该是 _displayedFavoriteIndex＆lt; 0 而不是 _displayedFavoriteIndex＆lt; = 0

private void BackwardButton_Tapped(object sender, TappedRoutedEventArgs e)
{
    if (FavoriteListBox.Items.Count > 1)
    {
        //move to the previous item
        _displayedFavoriteIndex--;
        if (_displayedFavoriteIndex < 0) // Change here
        {
            //we have reached the end of the list
            _displayedFavoriteIndex = listobj.Count - 1;
        }
        //show the item            
        DisplayTextBlock.Text = listobj[ _displayedFavoriteIndex ].AnswerName;
    }
}

后退按钮从收藏夹跳过第一项

2 个答案: