Windows Phone 8.1 RT在C＃中更改圖像源

Question

我想在運行時使用C＃更改圖像源。 我試過了

在MainPage.xaml中，

<Image x:Name="myImage" HorizontalAlignment="Left"
               Height="125"
               Margin="86,76,0,0"
               VerticalAlignment="Top"
               Width="220" />
        <Button Content="Button"
                HorizontalAlignment="Left"
                Margin="134,230,0,0"
                VerticalAlignment="Top"
                Click="Button_Click"/>

並在MainPage.xaml.cs中

private void Button_Click(object sender, RoutedEventArgs e)
        {
            myImage.Source = new BitmapImage(new Uri("/Assets/WorldCupFlags/Sri_Lanka.png", UriKind.Relative));
        }

它沒有顯示編譯時錯誤，但是當我運行它並單擊Button時，它顯示了異常。 它說：“ mscorlib.ni.dll中發生了'System.ArgumentException'類型的異常，但未在用戶代碼中處理。”

Answer 1

提示是例外：

給定的System.Uri無法轉換為Windows.Foundation.Uri

您需要為Universal XAML應用程序使用絕對URI：

myImage.Source = new BitmapImage(new Uri(
  "ms-appx:///Assets/WorldCupFlags/Sri_Lanka.png", UriKind.Absolute));

Answer 2

在異步代碼塊中，執行以下操作：

imgMyImageControl.Source = await GetBitmapAsFile("Folder\\ImageFileName.png");

GetBimpageAsFile函數：

    /// <summary>
    /// Gets a bitmap image stored on the local file system
    /// </summary>
    /// <param name="strIFile">The input file path name</param>
    /// <returns>The requested bitmap image, if successful; else, null</returns>
    public static async Task<BitmapImage> GetBitmapAsFile(string strIFile)
    {
        try
        {
            StorageFile fOut = null;
            BitmapImage biOut = null;
            FileRandomAccessStream fasGet = null;

            if (!strIFile.Equals(""))
            {
                fOut = await Windows.Storage.ApplicationData.Current.LocalFolder.GetFileAsync(strIFile);
                if (fOut != null)
                {
                    fasGet = (FileRandomAccessStream)await fOut.OpenAsync(FileAccessMode.Read);
                    if (fasGet != null)
                    {
                        biOut = new BitmapImage();

                        if (biOut != null)
                        {
                            await biOut.SetSourceAsync(fasGet);

                            return biOut;
                        }
                        else
                            YourApp.App.ShowMessage(true, "Error", "GetBitmapAsFile", "Bitmap [" + strIFile + "] is not set.");
                    }
                    else
                        YourApp.App.ShowMessage(true, "Error", "GetBitmapAsFile", "File stream [" + strIFile + "] is not set.");
                }
            }
            else
                YourApp.App.ShowMessage(true, "Error", "GetBitmapAsFile", "Input file path name is empty.");
        }
        catch (Exception ex)
        {
            YourApp.App.ShowMessage(true, "Error", "GetBitmapAsFile", "[" + strIFile + "] " + ex.Message);
        }

        return null;
    }