目录
- 打开系统文件选择器与文件过滤
- 打开指定文件夹
- 文件夹权限申请
- 创建文件夹
- 存储访问框架api
- 获取文件夹文件
- 和mediastore api的不同
存储访问框架，简称：saf， 就是系统文件选择器+文件操作api。先选择文件，在用文件操作api处理文件。系统文件选择器，就和windows的文件选择框一样。
其实绝大多数app,都不会使用这个东西，因为太不方便了。图片，视频，普通文件，需要用户去翻文件夹找，这样的用户体验实在太差了。所以大家都是用第三方的或者自己写一个文件选择器。
之所以讲saf，一，是因为android11以后，使用mediastore无法访问到非多媒体文件了，需要依赖saf了。二，外卡和sd卡的操作依赖于存储访问框架授权。
打开系统文件选择器与文件过滤
intent intent = new intent(intent.action_open_document);
intent.addcategory(intent.category_openable);
intent.settype("application/*");
startactivityforresult(intent, request_code)
settype的值是mime type, 可以是”image/*”, “*/*”, 其中*是通配符。”image/*”代码所有类型的图片。”*/*”代表所有类型的文件。
当只需要打开几种文件类型时，可以用intent.extra_mime_types。同时settype设成“*/*”。
intent intent = new intent(intent.action_open_document);
intent.addcategory(intent.category_openable);
intent.settype("*/*");
intent.putextra(intent.extra_mime_types, new string[] {
"application/pdf", // .pdf
"application/vnd.oasis.opendocument.text", // .odt
"text/plain" // .txt
});
startactivityforresult(intent, request_code)
intent.action_pick和action_get_content，也可以打开文件选择框。action_get_content更加宽泛，除了文件其他类型的内容还可以取。
intent intent = new intent(intent.action_pick,
android.provider.mediastore.images.media.external_content_uri);
intent.settype("image/*");
intent intent = new intent(intent.action_get_content);
intent.settype("image/*")
下面列举了所有的mime type:
private static final string[][] mime_types = new string[][]{
{"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"},
{"docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document"},
{"xls", "application/vnd.ms-excel"},
{"xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"},
{"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"},
{"ape", "audio/ape"},
{"flac", "audio/flac"},
{"m4u", "video/vnd.mpegurl"},
{"m4v", "video/x-m4v"},
{"mov", "video/quicktime"},
{"mp2", "audio/x-mpeg"},
{"mp3", "audio/x-mpeg"},
{"mp4", "video/mp4"},
{"mkv", "video/x-matroska"},
{"flv", "video/x-flv"},
{"divx", "video/x-divx"},
{"mpa", "video/mpeg"},
{"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"},
{"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"},
{"rar", "application/x-rar"},
{"", "*/*"}
};
打开指定文件夹
利用documentscontract.extra_initial_uri，在打开文件选择器的时候，跳转到指定文件夹。只有android 8以上才行。
uri uri = uri.parse("content://com.android.externalstorage.documents/document/primary:download");
intent intent = new intent(intent.action_open_document);
intent.addcategory(intent.category_openable);
intent.settype("*/*");
intent.putextra(documentscontract.extra_initial_uri, uri);
startactivityforresult(intent, 1);
文件夹权限申请
当需要读取非公共文件夹里面的文件时，可以申请授权，授权后保存uri，之后可以拼接这个uri操作文件夹里的所有文件。
尤其是sd卡，从android 5 开始文件的修改删除必须先授权，且必须通过svf框架接口才能操作。
可以使用extra_initial_uri，打开指定文件夹，让用户授权
intent intent = new intent(intent.action_open_document_tree);
uri uri = uri.parse("content://com.android.externalstorage.documents/document/primary:download");
intent.putextra(documentscontract.extra_initial_uri, uri);
startactivityforresult(intent)
需要注意的是，android 11以后，无法授权访问存储根目录，以及download/，android/, 这两个文件夹也无法授权。
创建文件夹
创建文件夹有两个情况，一个是在已授权的文件夹下，可以使用svf框架api。
documentscontract.createdocument()
还有一种是在无授权的文件夹下创建，那么可以直接指定类型和名字，通过跳系统选择框创建。
intent intent = new intent(intent.action_create_document);
intent.addcategory(intent.category_openable);
intent.settype("application/txt");
intent.putextra(intent.extra_title, "testfile.txt");
startactivityforresult(intent)
存储访问框架api
存储访问框架api，都在documentscontract里面，典型的有：
public static @nullable uri renamedocument(@nonnull contentresolver content,
@nonnull uri documenturi, @nonnull string displayname) throws filenotfoundexception {
}
/**
* delete the given document.
*
* @param documenturi document with {@link document#flag_supports_delete}
* @return if the document was deleted successfully.
*/
public static boolean deletedocument(@nonnull contentresolver content, @nonnull uri documenturi)
throws filenotfoundexception {
}
/**
* copies the given document.
*
* @param sourcedocumenturi document with {@link document#flag_supports_copy}
* @param targetparentdocumenturi document which will become a parent of the source
* document's copy.
* @return the copied document, or {@code null} if failed.
*/
public static @nullable uri copydocument(@nonnull contentresolver content,
@nonnull uri sourcedocumenturi, @nonnull uri targetparentdocumenturi)
throws filenotfoundexception {
}
/**
* moves the given document under a new parent.
*
* @param sourcedocumenturi document with {@link document#flag_supports_move}
* @param sourceparentdocumenturi parent document of the document to move.
* @param targetparentdocumenturi document which will become a new parent of the source
* document.
* @return the moved document, or {@code null} if failed.
*/
public static @nullable uri movedocument(@nonnull contentresolver content,
@nonnull uri sourcedocumenturi, @nonnull uri sourceparentdocumenturi,
@nonnull uri targetparentdocumenturi) throws filenotfoundexception {
}
/**
* removes the given document from a parent directory.
*
* <p>in contrast to {@link #deletedocument} it requires specifying the parent.
* this method is especially useful if the document can be in multiple parents.
*
* @param documenturi document with {@link document#flag_supports_remove}
* @param parentdocumenturi parent document of the document to remove.
* @return true if the document was removed successfully.
*/
public static boolean removedocument(@nonnull contentresolver content, @nonnull uri documenturi,
@nonnull uri parentdocumenturi) throws filenotfoundexception {
}
获取文件夹文件
使用documentfile类获取文件夹里文件列表。
private activityresultlauncher<object> openfile() {
intent intent = new intent(intent.action_open_document_tree);
uri uri = uri.parse("content://com.android.externalstorage.documents/document/primary:authsdk");
intent.putextra(documentscontract.extra_initial_uri, uri);
return startactivityforresult(intent, new activityresultcallback<intent>() {
@override
public void onactivityresult(intent result) {
for (documentfile documentfile : documentfile.fromtreeuri(baseapplication.getinstance().getapplicationcontext(), uri.parse(result.getdata().tostring())).listfiles()) {
log.i("", documentfile.geturi());
}
}
});
}
下面的代码演示了，使用svf读取文件内容，写内容，通过mediastore查询文件属性。
private activityresultlauncher<object> openfile() {
intent intent = new intent(intent.action_open_document_tree);
uri uri = uri.parse("content://com.android.externalstorage.documents/document/primary:authsdk");
intent.putextra(documentscontract.extra_initial_uri, uri);
return startactivityforresult(intent, new activityresultcallback<intent>() {
@override
public void onactivityresult(intent result) {
for (documentfile documentfile : documentfile.fromtreeuri(baseapplication.getinstance().getapplicationcontext(), uri.parse(result.getdata().tostring())).listfiles()) {
try {
inputstream inputstream = baseapplication.getinstance().getcontentresolver().openinputstream(documentfile.geturi());
byte[] readdata = new byte[1024];
inputstream.read(readdata);
outputstream outputstream = baseapplication.getinstance().getcontentresolver().openoutputstream(documentfile.geturi());
byte[] writedata = "alan gong".getbytes(standardcharsets.utf_8);
outputstream.write(writedata, 0, 9);
outputstream.close();
if (build.version.sdk_int >= build.version_codes.q) {
uri mediauri = mediastore.getmediauri(baseapplication.getinstance().getapplicationcontext(), documentfile.geturi());
long fileid = contenturis.parseid(mediauri);
cursor query = baseapplication.getinstance().getcontentresolver().query(documentfile.geturi(), null, mediastore.mediacolumns._id + "=" + fileid, null, null);
int columnindex = query.getcolumnindexorthrow(mediastore.mediacolumns.mime_type);
string mimetype = query.getstring(columnindex);
log.i("", "");
}
} catch (filenotfoundexception e) {
e.printstacktrace();
} catch (ioexception e) {
e.printstacktrace();
}
}
}
});
}
使用mediastore.getmediauri(documenturi)可以转换，mediastore uri 和 document uri。通过mediastore uri中的数据库id，就可以查询文件的所有属性了。
mediastore uri：content://media/external_primary/file/101750
document uri: content://com.android.externalstorage.documents/tree/primary%3aauthsdk
另外，
非公共目录下不能用file api操作的，即使通过svf授权了， read_extrnal_permission的权限也给了。还是会抛出filenotfoundexception， 并且显示permission deny。
和mediastore api的不同
存储访问框架api和mediastore api的差异，在于存储访问框架api，是基于系统文件选择框的，用户选择了文件，那么相当于授权了， 可以访问所有类型的文件。而mediastore的特点是可以查询出所有文件，但是开启分区存储后，只能查处多媒体文件，其他类型文件是不可以的。
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