windows 8 metro app 中 选中某个 item 弹出 appbar 的方法

最近写的程序想模拟win8中的右键单击某个磁贴就会弹出一个appbar来当作菜单设置的功能，就是类似如下的效果：



查了好久没弄好，最终让我试出来了，只需要更改一下属性即可。

以下是我的appbar的初始xaml代码：

<Page.BottomAppBar>
        <AppBar Background="#FF00B7EF" BorderBrush="#FF00B7EF" Name="myAppBar">
            <AppBar.Content>
                <Grid>
                    <StackPanel Orientation="Horizontal" HorizontalAlignment="Left">
                        <Button  Visibility="Collapsed" Name="remove" AutomationProperties.Name="删除该项目" Style="{StaticResource RemoveAppBarButtonStyle}" Click="remove_Click"/>
                        <Button Visibility="Collapsed" Name="removeAll" AutomationProperties.Name="删除所有项目" Style="{StaticResource RemoveAppBarButtonStyle}" Click="removeAll_Click"/>
                    </StackPanel>
                    <StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
                        <Button Name="about" AutomationProperties.Name="关于" Style="{StaticResource HomeAppBarButtonStyle}" Click="about_Click"></Button>
                        <Button Name="setting" AutomationProperties.Name="设置" Style="{StaticResource SettingsAppBarButtonStyle}" Click="setting_Click"></Button>
                        <Button Name="export" AutomationProperties.Name="导出为文本文件" Style="{StaticResource DownloadAppBarButtonStyle}" Click="export_Click"></Button>
                    </StackPanel>
                </Grid>
                
            </AppBar.Content>
        </AppBar>
    </Page.BottomAppBar>

代码中包含五个按钮，其中有两个是暂时不可见的，我要实现的功能是当右键单击（触发selectionchanged事件）某个Grid的某个item的时候，马上弹出appbar，进行相应的操作。

当触发selectionchanged事件的时候，如果选中了一个那么

indexNum = IndexView.SelectedIndex;
就会得到一个索引值，如果取消选中就会得到-1，所以在得到非-1值的时候，让remove和removeAll两个按钮可见，并让整个appbar可见（isOpen＝true）；在-1的时候，让其不可见，综上，只要加入这么几行代码：

if (indexNum != -1)
           {
               remove.Visibility = Windows.UI.Xaml.Visibility.Visible;
               removeAll.Visibility = Windows.UI.Xaml.Visibility.Visible;
               myAppBar.IsOpen = true;
           }
           else {
               remove.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
               removeAll.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
           }

相关c#代码如下：

        int indexNum = 0;
        private void remove_Click(object sender, RoutedEventArgs e)
        {

            myIndex.RemoveAt(indexNum);
            remove.Visibility = Windows.UI.Xaml.Visibility.Visible;
            removeAll.Visibility = Windows.UI.Xaml.Visibility.Visible;

        }

        private  void select(object sender, SelectionChangedEventArgs e)
        {
           indexNum = IndexView.SelectedIndex;
           

           if (indexNum != -1)
           {
               remove.Visibility = Windows.UI.Xaml.Visibility.Visible;
               removeAll.Visibility = Windows.UI.Xaml.Visibility.Visible;
               myAppBar.IsOpen = true;
           }
           else {
               remove.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
               removeAll.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
           }
           

        }

        private async void removeAll_Click(object sender, RoutedEventArgs e)
        {
            MessageDialog md = new MessageDialog("确定删除所有日记？");
            md.Commands.Add(new UICommand("确定", command =>
            {
                myIndex.Clear();

            }));
            md.Commands.Add(new UICommand("取消", command =>
            {
               //do nothing              
            }));

            await md.ShowAsync();

            
           
        }

最终效果：

在未选中之前：



选中Grid中的item之后：