问题
The only way to show current time updating regularly I found is to use timer. Of course, I can implement INotifyPropertyChanged
and some special property to be used on UI but this implementation AFAIK also needs Timer
. For example like here. Are there any better way to display current time?
Edit
To clarify: are there any declarative way to make it work in real time without timer using XAML syntax like this?
<Label Content="{x:Static s:DateTime.Now}" ContentStringFormat="G" />
Nothing stops me from using timer here. I just want to know if there are more elegant and compact way of implementing this.
回答1:
Using Task.Delay can produce an high CPU usage!
In the XAML code write this:
<Label Name="LiveTimeLabel" Content="%TIME%" HorizontalAlignment="Left" Margin="557,248,0,0" VerticalAlignment="Top" Height="55" Width="186" FontSize="36" FontWeight="Bold" Foreground="Red" />
Next in the xaml.cs write this:
[...]
public MainWindow()
{
InitializeComponent();
DispatcherTimer LiveTime = new DispatcherTimer();
LiveTime.Interval = TimeSpan.FromSeconds(1);
LiveTime.Tick += timer_Tick;
LiveTime.Start();
}
void timer_Tick(object sender, EventArgs e)
{
LiveTimeLabel.Content = DateTime.Now.ToString("HH:mm:ss");
}
[...]
回答2:
WPF is a static markup language. As far as I am aware there is not a mechanism available in pure XAML to provide the functionally you are looking for.
If you want to avoid using a timer directly you can abstract it away using Tasks.
MainWindow XAML:
<Window x:Class="AsyncTimer.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:AsyncTimer"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Label Content="{Binding CurrentTime}"></Label>
</Grid>
</Window>
Code behind:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new CurrentTimeViewModel();
}
}
public class CurrentTimeViewModel : INotifyPropertyChanged
{
private string _currentTime;
public CurrentTimeViewModel()
{
UpdateTime();
}
private async void UpdateTime()
{
CurrentTime = DateTime.Now.ToString("G");
await Task.Delay(1000);
UpdateTime();
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public string CurrentTime
{
get { return _currentTime; }
set { _currentTime = value; OnPropertyChanged(); }
}
}
This is probably one of the more succinct and certainly as "Modern" WPF you are going to get.
来源:https://stackoverflow.com/questions/51039348/show-current-time-wpf