我正在使用 UWP 開發(fā) Microsoft Store 應(yīng)用程序，并且使用 XAML 和 C#。我想用不透明動(dòng)畫隨機(jī)更改背景圖像。我的代碼在下面。該函數(shù)執(zhí)行與Task.Run(InitializeWorks); private async void InitializeWorks() { await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, async () => { BackgroundImage.Opacity = 0; try { while (true) { var backgroundImageFolder = await Windows.ApplicationModel.Package.Current.InstalledLocation.GetFolderAsync(@"Assets\BackgroundImages"); var backgroundImageFiles = await backgroundImageFolder.GetFilesAsync(); BackgroundImage.Source = new BitmapImage(new Uri(backgroundImageFiles[new Random().Next(0, backgroundImageFiles.Count)].Path)); for (double i = BackgroundImage.Opacity; i <= 0.1; i += 0.001) { BackgroundImage.Opacity = i; await Task.Delay(10); } await Task.Delay(5000); for (double i = BackgroundImage.Opacity; i >= 0; i -= 0.001) { BackgroundImage.Opacity = i; await Task.Delay(10); } } } catch (Exception e) { // } }); }我可以使用這段代碼的性能如何？這個(gè)異步任務(wù)有什么不便嗎？會(huì)出現(xiàn)什么錯(cuò)誤嗎？如何用XAML制作變化的動(dòng)畫？
3 回答
蕭十郎
TA貢獻(xiàn)1815條經(jīng)驗(yàn) 獲得超13個(gè)贊
帶有故事板的 XML 動(dòng)畫；
? ? <Storyboard x:Name="BackgroundImageStoryboardIncrease">
? ? ? ? <DoubleAnimation
? ? ? ? ? ? Storyboard.TargetName="BackgroundImage"
? ? ? ? ? ? Storyboard.TargetProperty="Opacity"
? ? ? ? ? ? From="0"
? ? ? ? ? ? To="0.15"
? ? ? ? ? ? Duration="0:0:2" />
? ? </Storyboard>
? ? <Storyboard x:Name="BackgroundImageStoryboardDecrease">
? ? ? ? <DoubleAnimation
? ? ? ? ? ? Storyboard.TargetName="BackgroundImage"
? ? ? ? ? ? Storyboard.TargetProperty="Opacity"
? ? ? ? ? ? From="0.15"
? ? ? ? ? ? To="0"
? ? ? ? ? ? Duration="0:0:2" />
? ? </Storyboard>
C# 更改事件并等待 10 秒：
? ? private async void InitializeFrontWorks()
? ? {
? ? ? ? // Animations
? ? ? ? DispatcherTimer dispatcherTimer = new DispatcherTimer
? ? ? ? {
? ? ? ? ? ? Interval = TimeSpan.FromSeconds(10)
? ? ? ? };
? ? ? ? var backgroundImageFolder = await Windows.ApplicationModel.Package.Current.InstalledLocation.GetFolderAsync(@"Assets\BackgroundImages");
? ? ? ? var backgroundImageFiles = await backgroundImageFolder.GetFilesAsync();
? ? ? ? AnimationBackgroundImage(backgroundImageFiles);
? ? ? ? dispatcherTimer.Tick += delegate
? ? ? ? {
? ? ? ? ? ? AnimationBackgroundImage(backgroundImageFiles);
? ? ? ? };
? ? ? ? dispatcherTimer.Start();
? ? }
? ? private void AnimationBackgroundImage(IReadOnlyList<StorageFile> backgroundImageFiles)
? ? {
? ? ? ? BackgroundImageStoryboardDecrease.Begin();
? ? ? ? BackgroundImageStoryboardDecrease.Completed += delegate
? ? ? ? {
? ? ? ? ? ? BackgroundImage.Source = new BitmapImage(new Uri(backgroundImageFiles[new Random().Next(0, backgroundImageFiles.Count)].Path));
? ? ? ? ? ? BackgroundImageStoryboardIncrease.Begin();
? ? ? ? };
? ? }
HUX布斯
TA貢獻(xiàn)1876條經(jīng)驗(yàn) 獲得超6個(gè)贊
您可以在 XAML 中設(shè)置以下動(dòng)畫：
<Page.Resources>
<Storyboard x:Name="MyStoryboard">
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="BackgroundImage">
<EasingDoubleKeyFrame KeyTime="0" Value="0"/>
<EasingDoubleKeyFrame KeyTime="0:0:3" Value="0.1"/>
<EasingDoubleKeyFrame KeyTime="0:0:6" Value="0"/>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</Page.Resources>
隱藏代碼：
可以使用StoryBoard.Begin來啟動(dòng)Opacity動(dòng)畫，動(dòng)畫有Completed事件?？梢杂嗛喫鼇肀O(jiān)聽動(dòng)畫是否完成。當(dāng)動(dòng)畫完成后，可以調(diào)用InitializeWorks()方法再次更改BackgroundImage。這種寫法替換您的While方法。
private async void InitializeWorks()
{
await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, async () =>
{
BackgroundImage.Opacity = 0;
try
{
var backgroundImageFolder = await Windows.ApplicationModel.Package.Current.InstalledLocation.GetFolderAsync(@"Assets\BackgroundImages");
var backgroundImageFiles = await backgroundImageFolder.GetFilesAsync();
BackgroundImage.Source = new BitmapImage(new Uri(backgroundImageFiles[new Random().Next(0, backgroundImageFiles.Count)].Path));
MyStoryboard.Begin();
MyStoryboard.Completed += MyStoryboard_Completed;
}
catch (Exception e)
{
//
}
});
}
private void MyStoryboard_Completed(object sender, object e)
{
InitializeWorks();
}
至尊寶的傳說
TA貢獻(xiàn)1789條經(jīng)驗(yàn) 獲得超10個(gè)贊
您無法在 XAML 中調(diào)用GetFolderAsync或GetFilesAsync，但我建議您將循環(huán)替換while為定期更改背景的DispatcherTimer 。
該Tick事件將在 UI 線程上引發(fā)，這意味著可以安全地在事件處理程序中訪問 UI 元素。異步方法不會(huì)阻塞。
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