从 url/http [Android Xamarin App]

问题描述

你好，你们中的任何人都可以发送一个工作代码来从 android Xamarin c # 上的给定 http 地址下载照片吗？ 首先，我需要为我的应用程序文件创建一个新文件夹。 我的目标是将文件从 Internet 下载到我的 Android 文件夹（最好使用原始名称保存此文件）。 下一步是在“ImageView”中显示该文件夹中的图像。 android中有权限也很重要，我不完全理解。 你们中的任何人都可以将其发送给我或帮助我理解并解释主题吗？

*实际上我有这个代码：

string address = "https://i.stack.imgur.com/X3V3w.png";
using (WebClient webClient = new WebClient())
{
     webClient.DownloadFileCompleted += WebClient_DownloadFileCompleted;
     webClient.DownloadFile(address,Path.Combine(pathDire,"MyNewImage1.png"));
     //System.Net.WebException: 'An exception occurred during a WebClient request.'
}

解决方法

从 url 加载图片并在 imageview 中显示。

 private void Btn1_Click(object sender,System.EventArgs e)
    {
        var imageBitmap = GetImageBitmapFromUrl("http://xamarin.com/resources/design/home/devices.png");
        imagen.SetImageBitmap(imageBitmap);
    }

    private Bitmap GetImageBitmapFromUrl(string url)
    {
        Bitmap imageBitmap = null;

        using (var webClient = new WebClient())
        {
            var imageBytes = webClient.DownloadData(url);
            if (imageBytes != null && imageBytes.Length > 0)
            {

                SavePicture("ImageName.jpg",imageBytes,"imagesFolder");
                imageBitmap = BitmapFactory.DecodeByteArray(imageBytes,imageBytes.Length);
            }
        }

        return imageBitmap;
    }

下载图片并保存到本地。

 private void SavePicture(string name,byte[] data,string location = "temp")
    {
        
        var documentsPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
        documentsPath = System.IO.Path.Combine(documentsPath,"Orders",location);
        Directory.CreateDirectory(documentsPath);

        string filePath = System.IO.Path.Combine(documentsPath,name);      
        using (FileStream fs = new FileStream(filePath,FileMode.OpenOrCreate))
        {             
            int length = data.Length;
            fs.Write(data,length);
        }
    }

您需要在WRITE_EXTERNAL_STORAGE中添加权限READ_EXTERNAL_STORAGE和AndroidMainfeast.xml，然后在Android 6.0中还需要运行时权限检查。

  private void checkpermission()
    {
        if (ContextCompat.CheckSelfPermission(this,Manifest.Permission.WriteExternalStorage) == (int)Permission.Granted)
        {
            // We have permission,go ahead and use the writeexternalstorage.
        }
        else
        {
            // writeexternalstorage permission is not granted. If necessary display rationale & request.
        }
        if (ContextCompat.CheckSelfPermission(this,Manifest.Permission.ReadExternalStorage) == (int)Permission.Granted)
        {
            // We have permission,go ahead and use the ReadExternalStorage.
        }
        else
        {
            // ReadExternalStorage permission is not granted. If necessary display rationale & request.
        }
    }