对于Xamarin Android(来自@HoaLe的回答)

public String getMimeType(Uri uri) {
    String mimeType = null;
    if (uri.Scheme.Equals(ContentResolver.SchemeContent))
    {
        ContentResolver cr = Application.Context.ContentResolver;
        mimeType = cr.GetType(uri);
    }
    else
    {
        String fileExtension = MimeTypeMap.GetFileExtensionFromUrl(uri.ToString());
        mimeType = MimeTypeMap.Singleton.GetMimeTypeFromExtension(
        fileExtension.ToLower());
    }
    return mimeType;
}

EDIT

我为此创建了一个小型库。 但是底层代码几乎是一样的。

它在GitHub上可用

MimeMagic-Android

2020年9月

使用芬兰湾的科特林

fun File.getMimeType(context: Context): String? {
    if (this.isDirectory) {
        return null
    }

    fun fallbackMimeType(uri: Uri): String? {
        return if (uri.scheme == ContentResolver.SCHEME_CONTENT) {
            context.contentResolver.getType(uri)
        } else {
            val extension = MimeTypeMap.getFileExtensionFromUrl(uri.toString())
            MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension.toLowerCase(Locale.getDefault()))
        }
    }

    fun catchUrlMimeType(): String? {
        val uri = Uri.fromFile(this)

        return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val path = Paths.get(uri.toString())
            try {
                Files.probeContentType(path) ?: fallbackMimeType(uri)
            } catch (ignored: IOException) {
                fallbackMimeType(uri)
            }
        } else {
            fallbackMimeType(uri)
        }
    }

    val stream = this.inputStream()
    return try {
        URLConnection.guessContentTypeFromStream(stream) ?: catchUrlMimeType()
    } catch (ignored: IOException) {
        catchUrlMimeType()
    } finally {
        stream.close()
    }
}

这似乎是最好的选择，因为它结合了前面的答案。

首先，它尝试使用URLConnection获取类型。guessContentTypeFromStream，但如果这个失败或返回null，它会尝试在Android O和以上使用mimetype

java.nio.file.Files
java.nio.file.Paths

否则，如果Android版本低于O或方法失败，它将使用ContentResolver和MimeTypeMap返回类型

I don't realize why MimeTypeMap.getFileExtensionFromUrl() has problems with spaces and some other characters, that returns "", but I just wrote this method to change the file name to an admit-able one. It's just playing with Strings. However, It kind of works. Through the method, the spaces existing in the file name is turned into a desirable character (which, here, is "x") via replaceAll(" ", "x") and other unsuitable characters are turned into a suitable one via URLEncoder. so the usage (according to the codes presented in the question and the selected answer) should be something like getMimeType(reviseUrl(url)).

private String reviseUrl(String url) {

        String revisedUrl = "";
        int fileNameBeginning = url.lastIndexOf("/");
        int fileNameEnding = url.lastIndexOf(".");

        String cutFileNameFromUrl = url.substring(fileNameBeginning + 1, fileNameEnding).replaceAll(" ", "x");

        revisedUrl = url.
                substring(0, fileNameBeginning + 1) +
                java.net.URLEncoder.encode(cutFileNameFromUrl) +
                url.substring(fileNameEnding, url.length());

        return revisedUrl;
    }

Intent myIntent = new Intent(android.content.Intent.ACTION_VIEW);
                        File file = new File(filePatch); 
                        Uri uris = Uri.fromFile(file);
                        String mimetype = null;
                        if 
(uris.getScheme().equals(ContentResolver.SCHEME_CONTENT)) {
                            ContentResolver cr = 
getApplicationContext().getContentResolver();
                            mimetype = cr.getType(uris);
                        } else {
                            String fileExtension = 
MimeTypeMap.getFileExtensionFromUrl(uris.toString());
mimetype =  MimeTypeMap.getSingleton().getMimeTypeFromExtension(fileExtension.toLowerCase());
                        }

// new processing the mime type out of Uri which may return null in some cases
String mimeType = getContentResolver().getType(uri);
// old processing the mime type out of path using the extension part if new way returned null
if (mimeType == null){mimeType URLConnection.guessContentTypeFromName(path);}

以下是我在我的Android应用程序中使用的解决方案:

public static String getMimeType(String url)
    {
        String extension = url.substring(url.lastIndexOf("."));
        String mimeTypeMap = MimeTypeMap.getFileExtensionFromUrl(extension);
        String mimeType = MimeTypeMap.getSingleton().getMimeTypeFromExtension(mimeTypeMap);
        return mimeType;
    }