Question

我正在尝试在Xamarin / Android中创建一个示例应用程序，它从Internet下载一个图像并在ImageView中显示它。但是在执行var imageContent = await httpClient.GetByteArrayAsync (ImageUrl);之后不久，UI /应用程序就会挂起。没有回电响应即将到来。我正在添加我的完整源代码供您参考。请帮我解决我的样本中的错误。

[Activity (Label = "ImageDownloadSample", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
    private const string ImageUrl = "http://www.olympusimage.com.sg/content/000006422.jpg";
    private ImageView imgView;
    protected override void OnCreate (Bundle bundle)
    {
        base.OnCreate (bundle);
        SetContentView (Resource.Layout.Main);


        var button = FindViewById<Button> (Resource.Id.downloadImage);
        imgView = FindViewById<ImageView>(Resource.Id.imageView);
        button.Click+=((sender, e) => 
             DownloadImageAsync());

    }

    private async void DownloadImageAsync()
    {
            var httpClient = new HttpClient ();
            imgView.SetImageResource (Android.Resource.Drawable.IcMenuGallery);

            var imageContent = await httpClient.GetByteArrayAsync (ImageUrl);
            var documentsPath = System.Environment.GetFolderPath (System.Environment.SpecialFolder.Personal);
            string localFilename = "mytestImage.jpg";
            string localPath = System.IO.Path.Combine (documentsPath, localFilename);
            File.WriteAllBytes (localPath, imageContent); 


            var localImage = new Java.IO.File (localFilename);
            if (localImage.Exists ()) {

                var bitmapImage = BitmapFactory.DecodeFile (localImage.AbsolutePath);
                imgView.SetImageBitmap (bitmapImage);


        }

    }
}

}

请帮助

Answer 1

他们有一个样本应用程序正是这样做的：https://github.com/xamarin/monodroid-samples/blob/master/AsyncImageAndroid/AsyncImageAndroid/MainActivity.cs

此外，您尝试下载的图片看起来非常庞大......我一定会得到一些更合理的东西，只是为了在尝试让事情发挥作用时将其视为错误。

Answer 2

我有同样的问题。检查异常！如果你有超时设置HttpClient.Timeout更大！

Answer 3

您可能需要设置事件处理程序：

button.Click+=(async (sender, e) => DownloadImageAsync());

表示它包含可以异步运行的代码

HttpClient无法在Xamarin / Android App中运行

3 个答案: