Xamarin 形式的文件下载 [英] File Download in Xamarin forms

问题描述

在 Xamarin.Forms 项目中，我试图从 blob 存储下载文件，我还需要将其保存在设备本地文件夹中并需要立即打开它.

In Xamarin.Forms project, I'm trying to download the file from the blob storage, also I need to save it in a device local folder and need to open it immediately.

我在打开文件时遇到此异常Fil:///LocalFolderUrlOfTheFile 通过 Intent.getData() 暴露在应用程序之外

I'm getting this exception while opening the file Fil:///LocalFolderUrlOfTheFile exposed beyond app through Intent.getData()

我仅在大于 Marshmallow 的 android 版本中遇到此异常.

I'm getting this exception only in android versions which are greater than Marshmallow.

这是我用来打开文件的代码:

Here are codes which i'm using to opening the file:

public void SaveandOpenFile(byte[] data, string fileName)
    {
        string externalStorageState = global::Android.OS.Environment.ExternalStorageState;
        var externalPath = global::Android.OS.Environment.ExternalStorageDirectory.Path + "/" + global::Android.OS.Environment.DirectoryDownloads + "/" + fileName;
        File.WriteAllBytes(externalPath, data);

        Java.IO.File file = new Java.IO.File(externalPath);
        file.SetReadable(true);

        string application = "";
        string extension = Path.GetExtension(externalPath);

        // get mimeTye
        switch (extension.ToLower())
        {
            case ".txt":
                application = "text/plain";
                break;
            case ".doc":
            case ".docx":
                application = "application/msword";
                break;
            case ".pdf":
                application = "application/pdf";
                break;
            case ".xls":
            case ".xlsx":
                application = "application/vnd.ms-excel";
                break;
            case ".jpg":
            case ".jpeg":
            case ".png":
                application = "image/jpeg";
                break;
            default:
                application = "*/*";
                break;
        }

        //Android.Net.Uri uri = Android.Net.Uri.Parse("file://" + filePath);
        Android.Net.Uri uri = Android.Net.Uri.FromFile(file);
        Intent intent = new Intent(Intent.ActionView);
        intent.SetDataAndType(uri, application);
        intent.SetFlags(ActivityFlags.ClearWhenTaskReset | ActivityFlags.NewTask);

        Forms.Context.StartActivity(intent);
    }

如果我遗漏了什么，请告诉我.提前致谢！

Please let me know if i'm missing something. Thanks in advance!

推荐答案

在新版本中，您不能在应用程序之外公开文件.你应该设置几件事情来做到这一点.请按照以下步骤操作:

You can't expose the File outside of your app in new versions. You should setup couple of things to do that. Follow these steps:

第 1 步: 转到您的 android 清单文件并在 application 标签内定义文件提供程序.

Step 1: Goto your android's manifest file and define file providers inside application tags.

<provider android:name="android.support.v4.content.FileProvider" 
android:authorities="${applicationId}.provider" android:exported="false" 
android:grantUriPermissions="true">
    <meta-data android:name="android.support.FILE_PROVIDER_PATHS" android:resource="@xml/provider_paths" />
</provider>

第 2 步:在 XML 中定义提供程序路径

Step 2: Define the Provider path in XML

1. 如果您的 Resources 文件夹中不存在 XML 文件夹，则创建该文件夹.
2. 创建一个 XML 文件(如果您完全按照上一步操作，则该文件的名称将为provider_paths.xml"

第 3 步:在您在第 2 步中创建的提供者路径 XML 文件中定义提供者文件路径

Step 3: Define the Provider file path in Provider Path XML file you created in Step 2

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="files" path="."/>
    <internal-path name="files" path="."/>
    <files-path name="files" path="."/>
</paths>

第 4 步:当您下载文件时，您应该将它们保存在您在第 3 步中定义的位置.我将文件保存在 android 中的以下根目录:

Step 4: When you download your file you should save them in location that you defined in Step 3. I save the file in android at root directory below:

root = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);

第五步: 打开文件，下面是我用来分享的方法.希望您理解并相应地进行更改:

Step 5: Opening the File, Following is the method that I'm using to share. Hope you understand and make changes on yours accordingly :

    public Task Share(string title, string message, string filePath)
    {
        var extension = filePath.Substring(filePath.LastIndexOf(".",StringComparison.InvariantCultureIgnoreCase) + 1).ToLower();
        var contentType = string.Empty;

        Java.IO.File file=new  Java.IO.File(filePath);
        var apkURI = FileProvider.GetUriForFile(context, context.ApplicationContext.PackageName+ ".provider", file);

        switch (extension)
        {
            case "pdf":
                contentType = "application/pdf";
                break;
            case "png":
                contentType = "image/png";
                break;
            default:
                contentType = "application/octetstream";
                break;
        }

        var intent = new Intent(Intent.ActionSend);

        intent.SetFlags(ActivityFlags.GrantReadUriPermission);

        intent.SetType(contentType);
        intent.PutExtra(Intent.ExtraStream, apkURI);
        intent.PutExtra(Intent.ExtraText, string.Empty);
        intent.PutExtra(Intent.ExtraSubject, message ?? string.Empty);


        var chooserIntent = Intent.CreateChooser(intent, title ?? string.Empty);
        chooserIntent.SetFlags(ActivityFlags.ClearTop);
        chooserIntent.SetFlags(ActivityFlags.NewTask);

        context.StartActivity(chooserIntent);

        return Task.FromResult(true);
    }

如果您需要任何帮助，请告诉我.

Let me know if you need any help.

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