android Q 使用 ACTION_OPEN_DOCUMENT_TREE 选择目录进行遍历文件夹下文件

前期准备-图片选择
- 获取
  我们都知道如何获取图片使用,使用如下代码即可打开一个系统的图片选择器
```
val intent = Intent(Intent.ACTION_OPEN_DOCUMENT)intent.addCategory(Intent.CATEGORY_OPENABLE)intent.type = "image/*"startActivityForResult(intent, PICK_PIC_REQUEST_CODE)
```
  然后在onActivityResult(requestCode: Int, resultCode: Int, data: Intent?)方法中使用val uri=data?.data获取到图片到uri
- 读取
  拿到图片uri后通过以下代码转化为bitmap对象(请注意如果选取到uri不是应用自身创建到文件,是需要读写权限的),拿到bitmap以后你就可以为所欲为了
```
//通过流转化成bitmap对象  val inputStream: InputStream? = contentResolver.openInputStream(uri)  val bitmap= BitmapFactory.decodeStream(inputStream)
```

如何获取文件夹

选择文件夹
我们知道了如何选择文件,那么选择文件夹呢?查找api可以发现android 为我们提供一个 Intent.ACTION_OPEN_DOCUMENT_TREE字面意思就知道是选择文件夹的,直接上代码
```
 val intent = Intent(Intent.ACTION_OPEN_DOCUMENT_TREE) startActivityForResult(intent, PICK_DIR_REQUEST_CODE)
```
获取文件夹uri
同文件获取一样,在onActivityResult(requestCode: Int, resultCode: Int, data: Intent?)方法中使用val uri=data?.data获取到文件夹uri,他可能长这样
```
   content://com.android.providers.downloads.documents/tree/downloads
```

读文件夹下内容
拿到文件夹的uri后就要进行遍历了,这时需要了解另一个类 DocumentFile,下面一起看如何根据uri获取文件夹下的文件,如有疑问请看注释

//获取onActivityResult中获取文件夹uri val uri = data?.data       val listUri = mutableListOf<Uri>()         uri?.let {  //content://com.android.providers.downloads.documents/tree/downloads    //基于文件夹uri构造DocumentFile,val documentFile = DocumentFile.fromTreeUri(this, it)//拿到文件夹下文件列表val list= documentFile?.listFiles()//遍历list?.forEach {  //文件名              it.name              //文件类型              it.type              //获取文件夹下的图片,并将图片uri保存              if (it.isFile&&it.canRead()&& MimeType.isImage(it.type))   {                    listUri.add(it.uri)                    println("${it.uri} ${it.name} ${it.type} " )                   }              }       }```* 拿到文件夹下uri列表以后怎么操作,都很容易了.

最后提供一个常用的文件类型判断类

 enum class MimeType(val value: String) {    _png("image/png"),    _jpeg("image/jpeg"),    _jpg("image/jpeg"),    _webp("image/webp"),    _gif("image/gif"),    _bmp("image/bmp"),    _3gp("video/3gpp"),    _apk("application/vnd.android.package-archive"),    _asf("video/x-ms-asf"),    _avi("video/x-msvideo"),    _bin("application/octet-stream"),    _c("text/plain"),    _class("application/octet-stream"),    _conf("text/plain"),    _cpp("text/plain"),    _doc("application/msword"),    _docx("application/vnd.openxmlformats-officedocument.wordprocessingml.document"),    _xls("application/vnd.ms-excel"),    _xlsx("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"),    _exe("application/octet-stream"),    _gtar("application/x-gtar"),    _gz("application/x-gzip"),    _h("text/plain"),    _htm("text/html"),    _html("text/html"),    _jar("application/java-archive"),    _java("text/plain"),    _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"),    _pps("application/vnd.ms-powerpoint"),    _ppt("application/vnd.ms-powerpoint"),    _pptx("application/vnd.openxmlformats-officedocument.presentationml.presentation"),    _prop("text/plain"),    _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/plain"),    _z("application/x-compress"),    _zip("application/x-zip-compressed"),    _0("*/*"),    ;    companion object {        fun isImage(mimeType: String?): Boolean {            return mimeType?.let {                _webp.value == mimeType ||                        _png.value == mimeType ||                        _jpeg.value == mimeType ||                        _jpg.value == mimeType ||                        _bmp.value == mimeType ||                        _gif.value == mimeType            } ?: false        }        fun isGif(mimeType: String?): Boolean {            return mimeType?.let {                _gif.value == mimeType            } ?: false        }        fun isApk(mimeType: String?) = mimeType?.let {            _apk.value == mimeType        } ?: false        fun isVideo(mimeType: String?) = mimeType?.let {            _m3u.value == mimeType || _avi.value == mimeType        } ?: false    }}

android Q 使用 ACTION_OPEN_DOCUMENT_TREE 选择目录进行遍历文件夹下文件

android Q 使用 ACTION_OPEN_DOCUMENT_TREE 选择目录进行遍历文件夹下文件

最后提供一个常用的文件类型判断类

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