在 WPF 中实现暂停

Question

这里有一个简单的WPF程序：

<!-- Updater.xaml -->
<Window x:Class="Update.Updater"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525"
        DataContext="{Binding RelativeSource={RelativeSource Self}}">
    <Grid>
        <StackPanel>
            <Button Click="Button_Click" Height="50"></Button>
            <Label Content="{Binding Label1Text}" Height="50"></Label>
            <Label Content="{Binding Label2Text}" Height="50"></Label>
        </StackPanel>
    </Grid>
</Window>
// Updater.xaml.cs
using System.Threading;
using System.Windows;
namespace Update
{
    public partial class Updater : Window
    {
        public Updater()
        {
            InitializeComponent();
        }
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Label1Text = "It is coming...";
            Thread.Sleep(3000);
            Label2Text = "It is here!";
        }
        public string Label1Text
        {
            get { return (string)GetValue(CategoryProperty); }
            set { SetValue(CategoryProperty, value); }
        }
        static readonly DependencyProperty CategoryProperty = DependencyProperty.Register("Label1Text", typeof(string), typeof(Updater));
        public string Label2Text
        {
            get { return (string)GetValue(Label2TextProperty); }
            set { SetValue(Label2TextProperty, value); }
        }
        static readonly DependencyProperty Label2TextProperty = DependencyProperty.Register("Label2Text", typeof(string), typeof(Updater));
    }
}

目的是当您单击该按钮时，第一个标签将显示 It is coming... 。然后程序休眠 3 秒钟，最后第二个标签显示 It is here! 。但是，下面的幼稚实现不起作用。如果运行它并单击按钮，则会发生以下情况：程序休眠 3 秒钟，然后同时显示两个标签文本。您知道如何更正程序以使其按预期运行吗？

Answer 1

Button_Click 由

UI 线程调用，您不应在其中执行任何需要超过几毫秒的操作，更不用说睡眠 3 秒了。在此期间不会处理消息，您的接口无响应，并且您的应用程序被系统视为"挂起"。

因此，该长处理任务应由另一个线程处理。

类似的东西（未经测试）：

private void Button_Click(object sender, RoutedEventArgs e)
{
    Label1Text = "It is coming...";
    var backgroundWorker = new BackgroundWorker();
    backgroundWorker.DoWork += (s,e) => { Thread.Sleep(3000); }
    backgroundWorker.RunWorkerCompleted += (s,e) => { Label2Text = "It is here!"; }
    backgroundWorker.RunWorkerAsync();
}

链接：

后台工作者

使用调度程序构建响应速度更快的应用程序

Answer 2

试试这个：

label1.Content = "waiting...";
label1.Dispatcher.Invoke(DispatcherPriority.Background, new Action(delegate()
   {
        label1.UpdateLayout();
    }));
System.Threading.Thread.Sleep(3000);
label1.Content = "done!";

Answer 3

您可以使用情节提要和关键帧动画来执行此操作。

http://msdn.microsoft.com/en-us/library/ms742868.aspx

这里有一个很好的例子——

http://msdn.microsoft.com/en-us/library/system.windows.media.animation.stringanimationusingkeyframes.aspx

<Button Name="myAnimatedButton" Margin="200"
  FontSize="16pt" FontFamily="Verdana">Some Text
  <Button.Triggers>
    <EventTrigger RoutedEvent="Button.Click">
      <BeginStoryboard>
        <Storyboard>
          <StringAnimationUsingKeyFrames 
            Storyboard.TargetName="myAnimatedButton" Storyboard.TargetProperty="(Button.Content)"
            Duration="0:0:8" FillBehavior="HoldEnd">
            <!-- All the key frames below are DiscreteStringKeyFrames. Discrete key frames create 
            sudden "jumps" between values (no interpolation). Only discrete key frames can be used 
            for String key frame animations. -->
            <DiscreteStringKeyFrame Value="" KeyTime="0:0:0" />
            <DiscreteStringKeyFrame Value="A" KeyTime="0:0:1" />
            <DiscreteStringKeyFrame Value="An" KeyTime="0:0:1.5" />
            <DiscreteStringKeyFrame Value="Ani" KeyTime="0:0:2" />
            <DiscreteStringKeyFrame Value="Anim" KeyTime="0:0:2.5" />
            <DiscreteStringKeyFrame Value="Anima" KeyTime="0:0:3" />
            <DiscreteStringKeyFrame Value="Animat" KeyTime="0:0:3.5" />
            <DiscreteStringKeyFrame Value="Animate" KeyTime="0:0:4" />
            <DiscreteStringKeyFrame Value="Animated" KeyTime="0:0:4.5" />
            <DiscreteStringKeyFrame Value="Animated " KeyTime="0:0:5" />
            <DiscreteStringKeyFrame Value="Animated T" KeyTime="0:0:5.5" />
            <DiscreteStringKeyFrame Value="Animated Te" KeyTime="0:0:6" />
            <DiscreteStringKeyFrame Value="Animated Tex" KeyTime="0:0:6.5" />
            <DiscreteStringKeyFrame Value="Animated Text" KeyTime="0:0:7" />
          </StringAnimationUsingKeyFrames>              
        </Storyboard>
      </BeginStoryboard>
    </EventTrigger> 
  </Button.Triggers>
</Button>