java - Android 中的 “Could not find a part of the path” 错误

Question

在我们开始之前，我知道很多人都提出了类似的问题，但我无法解决我的问题。

我尝试将位图保存到 Android 设备的图库中，但无法到达该特定路径。

这是代码:

string root = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
Java.IO.File myDir = new Java.IO.File(root + "/Screenshots");
myDir.Mkdirs();

string fname = "test_picture.jpg";

Java.IO.File file = new Java.IO.File(myDir, fname);
if (file.Exists())
    file.Delete();
try
{
    FileStream outStream = new FileStream(file.Path, FileMode.OpenOrCreate); //Seems like the problem is here
    finalBitmap.Compress(Bitmap.CompressFormat.Jpeg, 100, outStream);
    outStream.Flush();
    outStream.Close();
}
catch (Exception e)
{
    Toast.MakeText(Activity, e.ToString(), ToastLength.Long).Show();
}

我收到此错误:

System.IO.DirectoryNotFoundException: Could not find a part of the path "/storage/emulated/0/Screenshots/test_picture.jpg"

路径有什么问题吗？错误的根源是什么？

P.S:我已经授予了所有需要的权限。

Answer 1

I get the next error: System.IO.DirectoryNotFoundException: Could not find a part of the path "/storage/emulated/0/Screenshots/test_picture.jpg".

测试您的代码后，以下代码中发生此错误:

FileStream outStream = new FileStream(file.Path, FileMode.OpenOrCreate);

如果使用此 string root = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath; ，您应该注意到这是一个 Public external files .

/storage/emulated/0/Documents

根据文档，Android 应用程序必须获得权限才能读取或写入任何公共(public)文件。因此，您需要在 AndroidManifest.xml 中添加权限:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

并且从android 6.0开始，还需要添加运行时权限。这里，建议可以为项目安装Plugin.Permissions NuGet包来请求权限。如下是一个示例:

OnCreate():

Plugin.CurrentActivity.CrossCurrentActivity.Current.Init(this,savedInstanceState);

按钮点击方法():

try
{
    var status = await CrossPermissions.Current.CheckPermissionStatusAsync(Permission.Storage);
    if (status != PermissionStatus.Granted)
    {
        if (await CrossPermissions.Current.ShouldShowRequestPermissionRationaleAsync(Permission.Storage))
        {
            //await DisplayAlert("Need location", "Gunna need that location", "OK");
            Console.WriteLine("OK");
        }

        var results = await CrossPermissions.Current.RequestPermissionsAsync(Permission.Storage);
        //Best practice to always check that the key exists
        if (results.ContainsKey(Permission.Storage))
            status = results[Permission.Storage];
    }

    if (status == PermissionStatus.Granted)
    {
        string root = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
        Java.IO.File myDir = new Java.IO.File(root + "/Screenshots");
        myDir.Mkdirs();

        string fname = "test_picture.jpg";

        Java.IO.File file = new Java.IO.File(myDir, fname);
        Console.WriteLine("------root-------" + file.Path);

        FileStream outStream = new FileStream(file.Path, FileMode.OpenOrCreate);
        ....
    }
    else if (status != PermissionStatus.Unknown)
    {
        Console.WriteLine("OK");
        //await DisplayAlert("Location Denied", "Can not continue, try again.", "OK");
    }
}
catch (Exception ex)
{
    Console.WriteLine("" + ex);
}

其他解决方案:

如果不使用公共(public)外部文件，您可以尝试使用 Private external files

/storage/emulated/0/Android/data/com.companyname.app/files/

这不需要运行时权限。但是，还需要 AndroidManifest.xml 中的静态权限。

string root = Application.Context.GetExternalFilesDir("DirectoryPictures").ToString();