Android原生文件分享

创建分享

1. 创建Intent并指定Action为Intent.ACTION_SEND。

val shareIntent = Intent(Intent.ACTION_SEND)

2. 指定需要发送的内容和类型。

//传输文件 采用流的方式
intent.putExtra(Intent.EXTRA_STREAM,Uri.fromFile(File(fileUrl))
intent.type = "*/*"

3. 发送隐式意图，打开系统分享选择器。

context.startActivity(shareIntent)

获取文件类型（MimeType）

文件分享时一般都要设置好文件类型，默认指定类型为*/*，已默认类型进行分享时有些App不支持这种类型，会导致我们分享失败，最好的方式是预先根据文件路径设置好文件类型。

常见文件的mimeType

{".3gp", "video/3gpp"},  
{".apk", "application/vnd.android.package-archive"},  
{".asf", "video/x-ms-asf"},  
{".avi", "video/x-msvideo"},  
{".bin", "application/octet-stream"},  
{".bmp", "image/bmp"},  
{".c", "text/plain"},  
{".class", "application/octet-stream"},  
{".conf", "text/plain"},  
{".cpp", "text/plain"},  
{".doc", "application/msword"},  
{".exe", "application/octet-stream"},  
{".gif", "image/gif"},  
{".gtar", "application/x-gtar"},  
{".gz", "application/x-gzip"},  
{".h", "text/plain"},  
{".htm", "text/html"},  
{".html", "text/html"},  
{".jar", "application/java-archive"},  
{".java", "text/plain"},  
{".jpeg", "image/jpeg"},  
{".jpg", "image/jpeg"},  
{".js", "application/x-javascript"},  
{".log", "text/plain"},  
{".m3u", "audio/x-mpegurl"},  
{".m4a", "audio/mp4a-latm"},  
{".m4b", "audio/mp4a-latm"},  
{".m4p", "audio/mp4a-latm"},  
{".m4u", "video/vnd.mpegurl"},  
{".m4v", "video/x-m4v"},  
{".mov", "video/quicktime"},  
{".mp2", "audio/x-mpeg"},  
{".mp3", "audio/x-mpeg"},  
{".mp4", "video/mp4"},  
{".mpc", "application/vnd.mpohun.certificate"},  
{".mpe", "video/mpeg"},  
{".mpeg", "video/mpeg"},  
{".mpg", "video/mpeg"},  
{".mpg4", "video/mp4"},  
{".mpga", "audio/mpeg"},  
{".msg", "application/vnd.ms-outlook"},  
{".ogg", "audio/ogg"},  
{".pdf", "application/pdf"},  
{".png", "image/png"},  
{".pps", "application/vnd.ms-powerpoint"},  
{".ppt", "application/vnd.ms-powerpoint"},  
{".prop", "text/plain"},  
{".rar", "application/x-rar-compressed"},  
{".rc", "text/plain"},  
{".rmvb", "audio/x-pn-realaudio"},  
{".rtf", "application/rtf"},  
{".sh", "text/plain"},  
{".tar", "application/x-tar"},  
{".tgz", "application/x-compressed"},  
{".txt", "text/plain"},  
{".wav", "audio/x-wav"},  
{".wma", "audio/x-ms-wma"},  
{".wmv", "audio/x-ms-wmv"},  
{".wps", "application/vnd.ms-works"},  
{".xml", "text/xml"},  
{".xml", "text/plain"},  
{".z", "application/x-compress"},  
{".zip", "application/zip"},  
{"", "*/*"}  

方式一：通过 ContentResolver 查询 Android 系统提供的 ContentProvider 获取（方便但不稳定）

当 targetSdkVersion >= 24 时，
使用 Uri.fromFile(File file) 获取文件 URI 会报android.os.FileUriExposedException 异常

1. 获取文件的 url

val shareFile = File(shareFilePath)
val fileUri = Uri.fromFile(shareFile)

2. 获取系统的提供的 ContentResolver

val contentResolver = context!!.contentResolver

3. 获取文件MimeType，如 image/png

val fileMimeType = contentResolver.getType(fileUri)

4. 获取文件Type，如 txt

val mime = MimeTypeMap.getSingleton()
val fileType = mime.getExtensionFromMimeType(fileMimeType)

方式二：解析文件信息，通过匹配识别判断：

1. 识别文件后缀，根据后缀名来判断文件类型。
2. 获取文件头信息，转成十六进制字符串后判断文件类型。

object FileUtil {
    /**
     * 根据文件后缀回去MIME类型
     *
     * @param file file
     * @return string
     */
    public fun getMIMEType(file: File): String {
        var type = "*/*"
        val fName = file.name

        //获取后缀名前的分隔符"."在fName中的位置。
        val dotIndex = fName.lastIndexOf(".")
        if (dotIndex < 0) {
            return type
        }

        /* 获取文件的后缀名*/
        val end = fName.substring(dotIndex, fName.length).toLowerCase()
        if (TextUtils.isEmpty(end)) {
            return type
        }

        //在MIME和文件类型的匹配表中找到对应的MIME类型。
        for (i in MIME_MapTable.indices) {
            if (end == MIME_MapTable[i][0]) {
                type = MIME_MapTable[i][1]
                break
            }
        }
        return type
    }

    private val MIME_MapTable = arrayOf(
            // {后缀名，MIME类型}
            arrayOf(".3gp", "video/3gpp"),
            arrayOf(".apk", "application/vnd.android.package-archive"),
            arrayOf(".asf", "video/x-ms-asf"),
            arrayOf(".avi", "video/x-msvideo"),
            arrayOf(".bin", "application/octet-stream"),
            arrayOf(".bmp", "image/bmp"),
            arrayOf(".c", "text/plain"),
            arrayOf(".class", "application/octet-stream"),
            arrayOf(".conf", "text/plain"),
            arrayOf(".cpp", "text/plain"),
            arrayOf(".doc", "application/msword"),
            arrayOf(".docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document"),
            arrayOf(".xls", "application/vnd.ms-excel"),
            arrayOf(".xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"),
            arrayOf(".exe", "application/octet-stream"),
            arrayOf(".gif", "image/gif"),
            arrayOf(".gtar", "application/x-gtar"),
            arrayOf(".gz", "application/x-gzip"),
            arrayOf(".h", "text/plain"),
            arrayOf(".htm", "text/html"),
            arrayOf(".html", "text/html"),
            arrayOf(".jar", "application/java-archive"),
            arrayOf(".java", "text/plain"),
            arrayOf(".jpeg", "image/jpeg"),
            arrayOf(".jpg", "image/jpeg"), arrayOf(".js", "application/x-javascript"), arrayOf(".log", "text/plain"),
            arrayOf(".m3u", "audio/x-mpegurl"), arrayOf(".m4a", "audio/mp4a-latm"), arrayOf(".m4b", "audio/mp4a-latm"),
            arrayOf(".m4p", "audio/mp4a-latm"), arrayOf(".m4u", "video/vnd.mpegurl"), arrayOf(".m4v", "video/x-m4v"), arrayOf(".mov", "video/quicktime"),
            arrayOf(".mp2", "audio/x-mpeg"), arrayOf(".mp3", "audio/x-mpeg"), arrayOf(".mp4", "video/mp4"),
            arrayOf(".mpc", "application/vnd.mpohun.certificate"), arrayOf(".mpe", "video/mpeg"), arrayOf(".mpeg", "video/mpeg"),
            arrayOf(".mpg", "video/mpeg"), arrayOf(".mpg4", "video/mp4"), arrayOf(".mpga", "audio/mpeg"), arrayOf(".msg", "application/vnd.ms-outlook"),
            arrayOf(".ogg", "audio/ogg"),
            arrayOf(".pdf", "application/pdf"), arrayOf(".png", "image/png"), arrayOf(".pps", "application/vnd.ms-powerpoint"),
            arrayOf(".ppt", "application/vnd.ms-powerpoint"), arrayOf(".pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation"),
            arrayOf(".prop", "text/plain"),
            arrayOf(".rc", "text/plain"), arrayOf(".rmvb", "audio/x-pn-realaudio"), arrayOf(".rtf", "application/rtf"),
            arrayOf(".sh", "text/plain"),
            arrayOf(".tar", "application/x-tar"), arrayOf(".tgz", "application/x-compressed"), arrayOf(".txt", "text/plain"),
            arrayOf(".wav", "audio/x-wav"),
            arrayOf(".wma", "audio/x-ms-wma"), arrayOf(".wmv", "audio/x-ms-wmv"), arrayOf(".wps", "application/vnd.ms-works"),
            arrayOf(".xml", "text/plain"), arrayOf(".z", "application/x-compress"), arrayOf(".zip", "application/x-zip-compressed"), arrayOf("", "*/*"))
}