从JSON幻灯片图像

Question

我想创建一个图像幻灯片。这些照片是从json上的数据中获取的（如下所示）。 我尝试使用以下的代码：

DispatcherTimer playlistTimer1a = null; 
List<string> Images1a = new List<string>(); 

protected override void OnNavigatedTo(NavigationEventArgs e) 
{ 
    ImageSource1a(); 
} 

private async void ImageSource1a() 
     { 
      try 
      { 
       var httpClientHandler = new HttpClientHandler(); 
       httpClientHandler.Credentials = new System.Net.NetworkCredential("username", "password"); 
       var httpClient = new HttpClient(httpClientHandler); 
       string urlPath = "http://"; 
       var values = new List<KeyValuePair<string, string>> 
       { 
        new KeyValuePair<string, string>("platform","win"),  
       }; 
       HttpResponseMessage response = await httpClient.PostAsync(urlPath, new FormUrlEncodedContent(values)); 

       response.EnsureSuccessStatusCode(); 

       string jsonText = await response.Content.ReadAsStringAsync(); 
       JsonObject jsonObject = JsonObject.Parse(jsonText); 
       //JsonObject jsonData1 = jsonObject["data"].GetObject(); 

       JsonArray jsonData1 = jsonObject["data"].GetArray(); 

       foreach (JsonValue groupValue1 in jsonData1) 
       { 

        JsonObject groupObject1 = groupValue1.GetObject(); 

        string image = groupObject1["image"].GetString(); 
        string url = groupObject1["url"].GetString(); 

        Banner file1 = new Banner(); 
        file1.Image = image; 
        file1.URL = url; 
        Images1a.Add(file1.Image); 
        playlistTimer1a = new DispatcherTimer(); 
        playlistTimer1a.Interval = new TimeSpan(0, 0, 6); 
        playlistTimer1a.Tick += playlistTimer_Tick1a; 
        topBanner.Source = new BitmapImage(new Uri(file1.Image)); 
        playlistTimer1a.Start(); 
       } 
      } 
      catch (HttpRequestException ex) 
      { 
       RequestException(); 
      } 
     } 

int count1a = 0; 

void playlistTimer_Tick1a(object sender, object e) 
     { 
      if (Images1a != null) 
      { 
       if (count1a < Images1a.Count) 
        count1a++; 

       if (count1a >= Images1a.Count) 
        count1a = 0; 

       ImageRotation1a(); 
      } 
     } 

private async void ImageRotation1a() 
     { 
      OpacityTrans1.Begin(); 
     } 

而问题是只幻灯片放映显示图像索引为0只，不能改变图片。我怎样才能克服这个问题？

Answer 1

而问题是只有幻灯片显示图像索引只有0，不能更改图片。

的foreach环打破everything.If要进行幻灯片播放的图像，不包括DispatcherTimer在foreach循环，您可以通过以下步骤修改您的代码：

1. 修改您ImageSource1a方法如下图所示：

   private async void ImageSource1a() 
   { 
       try 
       { 
        ... 
        foreach (JsonValue groupValue1 in jsonData1) 
        { 
         JsonObject groupObject1 = groupValue1.GetObject(); 
         string image = groupObject1["image"].GetString(); 
         string url = groupObject1["url"].GetString(); 
         Images1a.Add(image); 
        } 
         //I don't know what is Banner object used for but for this piece of codes, a banner object is not necessary. 
         //Banner file1 = new Banner(); 
         //file1.Image = image; 
         //file1.URL = url; 
   
         playlistTimer1a = new DispatcherTimer(); 
         playlistTimer1a.Interval = new TimeSpan(0, 0, 6); 
         playlistTimer1a.Tick += playlistTimer_Tick1a; 
         topBanner.Source = new BitmapImage(new Uri(Images1a[0]));//set the current image to the first one 
         playlistTimer1a.Start(); 
       } 
       catch (HttpRequestException ex) 
       { 
        RequestException(); 
       } 
   } 
   

2. 修改您的playlistTimer_Tick1a方法如下图所示：

   private void playlistTimer_Tick1a(object sender, object e) 
   { 
       if (Images1a != null) 
       { 
   
        if (count1a < Images1a.Count) 
         count1a++; 
   
        if (count1a >= Images1a.Count) 
         count1a = 0; 
        topBanner.Source = new BitmapImage(new Uri(Images1a[count1a])); 
        ImageRotation1a(); 
       } 
   } 
   

更新：这里是我的基本演示：SlideShowSample。