一、前言

Android 4.4（API级别19）引入了存储访问框架（SAF）。
通过SAF，用户可以轻松地浏览和打开所有首选文档存储提供商中的文档，图像和其他文件。
也就是说，接下来介绍的方式适用于android4.4+的操作系统。
参考链接：https://developer.android.com/guide/topics/providers/document-provider

二、详细实现

1、调出系统文件管理器界面

private static final int READ_REQUEST_CODE = 42;
...
/*** Fires an intent to spin up the "file chooser" UI and select an image.*/
public void performFileSearch() {// ACTION_OPEN_DOCUMENT is the intent to choose a file via the system's file// browser.Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);// Filter to only show results that can be "opened", such as a// file (as opposed to a list of contacts or timezones)intent.addCategory(Intent.CATEGORY_OPENABLE);// Filter to show only images, using the image MIME data type.// If one wanted to search for ogg vorbis files, the type would be "audio/ogg".// To search for all documents available via installed storage providers,// it would be "*/*".intent.setType("image/*");startActivityForResult(intent, READ_REQUEST_CODE);
}

1）Intent除了可以设置为ACTION_OPEN_DOCUMEN，还可以替换为ACTION_GET_CONTENT ，两者的区别如下：

• 如果您希望您的应用仅读取/导入数据，请使用ACTION_GET_CONTENT。 通过这种方法，应用程序可以导入数据的副本，例如图像文件。
• 如果希望您的应用对文件提供者拥有的文件具有长期，持久的访问权限，请使用ACTION_OPEN_DOCUMENT。

2）Category设置为CATEGORY_OPENABLE，过滤出可以打开的文件

3）Type设置的是MIMETYPE,比如:

• 过滤所有图片，则设置为："image/*"
• 只过滤png图片，则设置为："image/png"
• 过滤apk，那么可设置为："application/vnd.android.package-archive"

4）startActivityForResult 启动Inetent,以便在onActivityResult接收文件选择结果

2、在onActivityResult中处理返回结果

@Override
public void onActivityResult(int requestCode, int resultCode,Intent resultData) {// The ACTION_OPEN_DOCUMENT intent was sent with the request code// READ_REQUEST_CODE. If the request code seen here doesn't match, it's the// response to some other intent, and the code below shouldn't run at all.if (requestCode == READ_REQUEST_CODE && resultCode == Activity.RESULT_OK) {// The document selected by the user won't be returned in the intent.// Instead, a URI to that document will be contained in the return intent// provided to this method as a parameter.// Pull that URI using resultData.getData().Uri uri = null;if (resultData != null) {uri = resultData.getData();Log.i(TAG, "Uri: " + uri.toString());showImage(uri);}}
}

1）从Intent中getData()获取到返回的Uri对象，旧版本是file://开头，新版本是content://开头

3、从Uri获取所需的信息

1）从Uri中获取文件元数据，一般只能获取到文件名与大小

public void dumpImageMetaData(Uri uri) {// The query, since it only applies to a single document, will only return// one row. There's no need to filter, sort, or select fields, since we want// all fields for one document.Cursor cursor = getActivity().getContentResolver().query(uri, null, null, null, null, null);try {// moveToFirst() returns false if the cursor has 0 rows.  Very handy for// "if there's anything to look at, look at it" conditionals.if (cursor != null && cursor.moveToFirst()) {// Note it's called "Display Name".  This is// provider-specific, and might not necessarily be the file name.String displayName = cursor.getString(cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME));Log.i(TAG, "Display Name: " + displayName);int sizeIndex = cursor.getColumnIndex(OpenableColumns.SIZE);// If the size is unknown, the value stored is null.  But since an// int can't be null in Java, the behavior is implementation-specific,// which is just a fancy term for "unpredictable".  So as// a rule, check if it's null before assigning to an int.  This will// happen often:  The storage API allows for remote files, whose// size might not be locally known.String size = null;if (!cursor.isNull(sizeIndex)) {// Technically the column stores an int, but cursor.getString()// will do the conversion automatically.size = cursor.getString(sizeIndex);} else {size = "Unknown";}Log.i(TAG, "Size: " + size);}} finally {cursor.close();}
}

2）将Uri转换为Bitmap

private Bitmap getBitmapFromUri(Uri uri) throws IOException {ParcelFileDescriptor parcelFileDescriptor =getContentResolver().openFileDescriptor(uri, "r");FileDescriptor fileDescriptor = parcelFileDescriptor.getFileDescriptor();Bitmap image = BitmapFactory.decodeFileDescriptor(fileDescriptor);parcelFileDescriptor.close();return image;
}

3)将Uri转换为InputStream

private String readTextFromUri(Uri uri) throws IOException {StringBuilder stringBuilder = new StringBuilder();try (InputStream inputStream =getContentResolver().openInputStream(uri);BufferedReader reader = new BufferedReader(new InputStreamReader(Objects.requireNonNull(inputStream)))) {String line;while ((line = reader.readLine()) != null) {stringBuilder.append(line);}}return stringBuilder.toString();
}

MIMETYPE 常见的用法：

文件类型	mime名称	文件类型	mime名称
3gp	video/3gpp	pdb	chemical/x-pdb
aab	application/x-authoware-bin	pdf	application/pdf
aam	application/x-authoware-map	pfr	application/font-tdpfr
aas	application/x-authoware-seg	pgm	image/x-portable-graymap
ai	application/postscript	pict	image/x-pict
aif	audio/x-aiff	pm	application/x-perl
aifc	audio/x-aiff	pmd	application/x-pmd
aiff	audio/x-aiff	png	image/png
als	audio/X-Alpha5	pnm	image/x-portable-anymap
amc	application/x-mpeg	pnz	image/png
ani	application/octet-stream	pot	application/vnd.ms-powerpoint
apk	application/vnd.android.package-archive	ppm	image/x-portable-pixmap
asc	text/plain	pps	application/vnd.ms-powerpoint
asd	application/astound	ppt	application/vnd.ms-powerpoint
asf	video/x-ms-asf	pqf	application/x-cprplayer
asn	application/astound	pqi	application/cprplayer
asp	application/x-asap	prc	application/x-prc
asx	video/x-ms-asf	proxy	application/x-ns-proxy-autoconfig
au	audio/basic	ps	application/postscript
avb	application/octet-stream	ptlk	application/listenup
avi	video/x-msvideo	pub	application/x-mspublisher
awb	audio/amr-wb	pvx	video/x-pv-pvx
bcpio	application/x-bcpio	qcp	audio/vnd.qcelp
bin	application/octet-stream	qt	video/quicktime
bld	application/bld	qti	image/x-quicktime
bld2	application/bld2	qtif	image/x-quicktime
bmp	image/bmp	r3t	text/vnd.rn-realtext3d
bpk	application/octet-stream	ra	audio/x-pn-realaudio
bz2	application/x-bzip2	ram	audio/x-pn-realaudio
cal	image/x-cals	rar	application/x-rar-compressed
ccn	application/x-cnc	ras	image/x-cmu-raster
cco	application/x-cocoa	rdf	application/rdf+xml
cdf	application/x-netcdf	rf	image/vnd.rn-realflash
cgi	magnus-internal/cgi	rgb	image/x-rgb
chat	application/x-chat	rlf	application/x-richlink
class	application/octet-stream	rm	audio/x-pn-realaudio
clp	application/x-msclip	rmf	audio/x-rmf
cmx	application/x-cmx	rmm	audio/x-pn-realaudio
co	application/x-cult3d-object	rmvb	audio/x-pn-realaudio
cod	image/cis-cod	rnx	application/vnd.rn-realplayer
cpio	application/x-cpio	roff	application/x-troff
cpt	application/mac-compactpro	rp	image/vnd.rn-realpix
crd	application/x-mscardfile	rpm	audio/x-pn-realaudio-plugin
csh	application/x-csh	rt	text/vnd.rn-realtext
csm	chemical/x-csml	rte	x-lml/x-gps
csml	chemical/x-csml	rtf	application/rtf
css	text/css	rtg	application/metastream
cur	application/octet-stream	rtx	text/richtext
dcm	x-lml/x-evm	rv	video/vnd.rn-realvideo
dcr	application/x-director	rwc	application/x-rogerwilco
dcx	image/x-dcx	s3m	audio/x-mod
dhtml	text/html	s3z	audio/x-mod
dir	application/x-director	sca	application/x-supercard
dll	application/octet-stream	scd	application/x-msschedule
dmg	application/octet-stream	sdf	application/e-score
dms	application/octet-stream	sea	application/x-stuffit
doc	application/msword	sgm	text/x-sgml
dot	application/x-dot	sgml	text/x-sgml
dvi	application/x-dvi	sh	application/x-sh
dwf	drawing/x-dwf	shar	application/x-shar
dwg	application/x-autocad	shtml	magnus-internal/parsed-html
dxf	application/x-autocad	shw	application/presentations
dxr	application/x-director	si6	image/si6
ebk	application/x-expandedbook	si7	image/vnd.stiwap.sis
emb	chemical/x-embl-dl-nucleotide	si9	image/vnd.lgtwap.sis
embl	chemical/x-embl-dl-nucleotide	sis	application/vnd.symbian.install
eps	application/postscript	sit	application/x-stuffit
eri	image/x-eri	skd	application/x-Koan
es	audio/echospeech	skm	application/x-Koan
esl	audio/echospeech	skp	application/x-Koan
etc	application/x-earthtime	skt	application/x-Koan
etx	text/x-setext	slc	application/x-salsa
evm	x-lml/x-evm	smd	audio/x-smd
evy	application/x-envoy	smi	application/smil
exe	application/octet-stream	smil	application/smil
fh4	image/x-freehand	smp	application/studiom
fh5	image/x-freehand	smz	audio/x-smd
fhc	image/x-freehand	snd	audio/basic
fif	image/fif	spc	text/x-speech
fm	application/x-maker	spl	application/futuresplash
fpx	image/x-fpx	spr	application/x-sprite
fvi	video/isivideo	sprite	application/x-sprite
gau	chemical/x-gaussian-input	spt	application/x-spt
gca	application/x-gca-compressed	src	application/x-wais-source
gdb	x-lml/x-gdb	stk	application/hyperstudio
gif	image/gif	stm	audio/x-mod
gps	application/x-gps	sv4cpio	application/x-sv4cpio
gtar	application/x-gtar	sv4crc	application/x-sv4crc
gz	application/x-gzip	svf	image/vnd
hdf	application/x-hdf	svg	image/svg-xml
hdm	text/x-hdml	svh	image/svh
hdml	text/x-hdml	svr	x-world/x-svr
hlp	application/winhlp	swf	application/x-shockwave-flash
hqx	application/mac-binhex40	swfl	application/x-shockwave-flash
htm	text/html	t	application/x-troff
html	text/html	tad	application/octet-stream
hts	text/html	talk	text/x-speech
ice	x-conference/x-cooltalk	tar	application/x-tar
ico	application/octet-stream	taz	application/x-tar
ief	image/ief	tbp	application/x-timbuktu
ifm	image/gif	tbt	application/x-timbuktu
ifs	image/ifs	tcl	application/x-tcl
imy	audio/melody	tex	application/x-tex
ins	application/x-NET-Install	texi	application/x-texinfo
ips	application/x-ipscript	texinfo	application/x-texinfo
ipx	application/x-ipix	tgz	application/x-tar
it	audio/x-mod	thm	application/vnd.eri.thm
itz	audio/x-mod	tif	image/tiff
ivr	i-world/i-vrml	tiff	image/tiff
j2k	image/j2k	tki	application/x-tkined
jad	text/vnd.sun.j2me.app-descriptor	tkined	application/x-tkined
jam	application/x-jam	toc	application/toc
jar	application/java-archive	toy	image/toy
jnlp	application/x-java-jnlp-file	tr	application/x-troff
jpe	image/jpeg	trk	x-lml/x-gps
jpeg	image/jpeg	trm	application/x-msterminal
jpg	image/jpeg	tsi	audio/tsplayer
jpz	image/jpeg	tsp	application/dsptype
js	application/x-javascript	tsv	text/tab-separated-values
jwc	application/jwc	tsv	text/tab-separated-values
kjx	application/x-kjx	ttf	application/octet-stream
lak	x-lml/x-lak	ttz	application/t-time
latex	application/x-latex	txt	text/plain
lcc	application/fastman	ult	audio/x-mod
lcl	application/x-digitalloca	ustar	application/x-ustar
lcr	application/x-digitalloca	uu	application/x-uuencode
lgh	application/lgh	uue	application/x-uuencode
lha	application/octet-stream	vcd	application/x-cdlink
lml	x-lml/x-lml	vcf	text/x-vcard
lmlpack	x-lml/x-lmlpack	vdo	video/vdo
lsf	video/x-ms-asf	vib	audio/vib
lsx	video/x-ms-asf	viv	video/vivo
lzh	application/x-lzh	vivo	video/vivo
m13	application/x-msmediaview	vmd	application/vocaltec-media-desc
m14	application/x-msmediaview	vmf	application/vocaltec-media-file
m15	audio/x-mod	vmi	application/x-dreamcast-vms-info
m3u	audio/x-mpegurl	vms	application/x-dreamcast-vms
m3url	audio/x-mpegurl	vox	audio/voxware
ma1	audio/ma1	vqe	audio/x-twinvq-plugin
ma2	audio/ma2	vqf	audio/x-twinvq
ma3	audio/ma3	vql	audio/x-twinvq
ma5	audio/ma5	vre	x-world/x-vream
man	application/x-troff-man	vrml	x-world/x-vrml
map	magnus-internal/imagemap	vrt	x-world/x-vrt
mbd	application/mbedlet	vrw	x-world/x-vream
mct	application/x-mascot	vts	workbook/formulaone
mdb	application/x-msaccess	wav	audio/x-wav
mdz	audio/x-mod	wax	audio/x-ms-wax
me	application/x-troff-me	wbmp	image/vnd.wap.wbmp
mel	text/x-vmel	web	application/vnd.xara
mi	application/x-mif	wi	image/wavelet
mid	audio/midi	wis	application/x-InstallShield
midi	audio/midi	wm	video/x-ms-wm
mif	application/x-mif	wma	audio/x-ms-wma
mil	image/x-cals	wmd	application/x-ms-wmd
mio	audio/x-mio	wmf	application/x-msmetafile
mmf	application/x-skt-lbs	wml	text/vnd.wap.wml
mng	video/x-mng	wmlc	application/vnd.wap.wmlc
mny	application/x-msmoney	wmls	text/vnd.wap.wmlscript
moc	application/x-mocha	wmlsc	application/vnd.wap.wmlscriptc
mocha	application/x-mocha	wmlscript	text/vnd.wap.wmlscript
mod	audio/x-mod	wmv	audio/x-ms-wmv
mof	application/x-yumekara	wmx	video/x-ms-wmx
mol	chemical/x-mdl-molfile	wmz	application/x-ms-wmz
mop	chemical/x-mopac-input	wpng	image/x-up-wpng
mov	video/quicktime	wpt	x-lml/x-gps
movie	video/x-sgi-movie	wri	application/x-mswrite
mp2	audio/x-mpeg	wrl	x-world/x-vrml
mp3	audio/x-mpeg	wrz	x-world/x-vrml
mp4	video/mp4	ws	text/vnd.wap.wmlscript
mpc	application/vnd.mpohun.certificate	wsc	application/vnd.wap.wmlscriptc
mpe	video/mpeg	wv	video/wavelet
mpeg	video/mpeg	wvx	video/x-ms-wvx
mpg	video/mpeg	wxl	application/x-wxl
mpg4	video/mp4	x-gzip	application/x-gzip
mpga	audio/mpeg	xar	application/vnd.xara
mpn	application/vnd.mophun.application	xbm	image/x-xbitmap
mpp	application/vnd.ms-project	xdm	application/x-xdma
mps	application/x-mapserver	xdma	application/x-xdma
mrl	text/x-mrml	xdw	application/vnd.fujixerox.docuworks
mrm	application/x-mrm	xht	application/xhtml+xml
ms	application/x-troff-ms	xhtm	application/xhtml+xml
mts	application/metastream	xhtml	application/xhtml+xml
mtx	application/metastream	xla	application/vnd.ms-excel
mtz	application/metastream	xlc	application/vnd.ms-excel
mzv	application/metastream	xll	application/x-excel
nar	application/zip	xlm	application/vnd.ms-excel
nbmp	image/nbmp	xls	application/vnd.ms-excel
nc	application/x-netcdf	xlt	application/vnd.ms-excel
ndb	x-lml/x-ndb	xlw	application/vnd.ms-excel
ndwn	application/ndwn	xm	audio/x-mod
nif	application/x-nif	xml	text/xml
nmz	application/x-scream	xmz	audio/x-mod
nokia-op-logo	image/vnd.nok-oplogo-color	xpi	application/x-xpinstall
npx	application/x-netfpx	xpm	image/x-xpixmap
nsnd	audio/nsnd	xsit	text/xml
nva	application/x-neva1	xsl	text/xml
oda	application/oda	xul	text/xul
oom	application/x-AtlasMate-Plugin	xwd	image/x-xwindowdump
pac	audio/x-pac	xyz	chemical/x-pdb
pae	audio/x-epac	yz1	application/x-yz1
pan	application/x-pan	z	application/x-compress
pbm	image/x-portable-bitmap	zac	application/x-zaurus-zac
pcx	image/x-pcx	zip	application/zip

三、文件创建、编辑与删除

1、创建文件，可以在onActivity中接收到结果

// Here are some examples of how you might call this method.
// The first parameter is the MIME type, and the second parameter is the name
// of the file you are creating:
//
// createFile("text/plain", "foobar.txt");
// createFile("image/png", "mypicture.png");// Unique request code.
private static final int WRITE_REQUEST_CODE = 43;
...
private void createFile(String mimeType, String fileName) {Intent intent = new Intent(Intent.ACTION_CREATE_DOCUMENT);// Filter to only show results that can be "opened", such as// a file (as opposed to a list of contacts or timezones).intent.addCategory(Intent.CATEGORY_OPENABLE);// Create a file with the requested MIME type.intent.setType(mimeType);intent.putExtra(Intent.EXTRA_TITLE, fileName);startActivityForResult(intent, WRITE_REQUEST_CODE);
}

2、获取Uri之后，要是文件的Document.COLUMN_FLAGS 包含SUPPORTS_DELETE，则可以删除该文件：

DocumentsContract.deleteDocument(getContentResolver(), uri);

3、编辑文件

private static final int EDIT_REQUEST_CODE = 44;
/*** Open a file for writing and append some text to it.*/private void editDocument() {// ACTION_OPEN_DOCUMENT is the intent to choose a file via the system's// file browser.Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);// Filter to only show results that can be "opened", such as a// file (as opposed to a list of contacts or timezones).intent.addCategory(Intent.CATEGORY_OPENABLE);// Filter to show only text files.intent.setType("text/plain");startActivityForResult(intent, EDIT_REQUEST_CODE);
}private void alterDocument(Uri uri) {try {ParcelFileDescriptor pfd = getActivity().getContentResolver().openFileDescriptor(uri, "w");FileOutputStream fileOutputStream =new FileOutputStream(pfd.getFileDescriptor());fileOutputStream.write(("Overwritten by MyCloud at " +System.currentTimeMillis() + "\n").getBytes());// Let the document provider know you're done by closing the stream.fileOutputStream.close();pfd.close();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}
}

4、检查最新的文件数据

final int takeFlags = intent.getFlags()& (Intent.FLAG_GRANT_READ_URI_PERMISSION| Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
// Check for the freshest data.
getContentResolver().takePersistableUriPermission(uri, takeFlags);

四、拓展

1、Android 7.0在存储访问框架中添加了虚拟文件的概念。
2、即使虚拟文件没有二进制表示形式，您的客户端应用程序也可以通过将其强制转换为其他文件类型或使用ACTION_VIEW意图查看这些文件来打开其内容。
3、要打开虚拟文件，您的客户端应用程序需要包含特殊的逻辑来处理它们。如果要获取文件的字节表示形式（例如，预览文件），则需要从文档提供者处请求其他MIME类型。
4、要在您的应用程序中获取虚拟文档的URI，首先要创建一个Intent以打开文件选择器UI，就像前面在Seach中为文档显示的代码一样。
5、重要提示：由于应用无法使用openInputStream（）方法直接打开虚拟文件，因此，如果您在ACTION_OPEN_DOCUMENT意向中包括CATEGORY_OPENABLE类别，则您的应用将不会收到任何虚拟文件。用户做出选择后，系统将调用onActivityResult（）方法，如先前在处理结果中所示。您的应用可以检索文件的URI，然后使用类似于以下代码片段的方法来确定文件是否为虚拟文件。验证文件为虚拟文件后，可以将其强制转换为其他MIME类型，例如图像文件。以下代码段显示了如何检查虚拟文件是否可以表示为映像，如果可以，则从虚拟文件获取输入流。

private boolean isVirtualFile(Uri uri) {if (!DocumentsContract.isDocumentUri(this, uri)) {return false;}Cursor cursor = getContentResolver().query(uri,new String[] { DocumentsContract.Document.COLUMN_FLAGS },null, null, null);int flags = 0;if (cursor.moveToFirst()) {flags = cursor.getInt(0);}cursor.close();return (flags & DocumentsContract.Document.FLAG_VIRTUAL_DOCUMENT) != 0;
}private InputStream getInputStreamForVirtualFile(Uri uri, String mimeTypeFilter)throws IOException {ContentResolver resolver = getContentResolver();String[] openableMimeTypes = resolver.getStreamTypes(uri, mimeTypeFilter);if (openableMimeTypes == null ||openableMimeTypes.length < 1) {throw new FileNotFoundException();}return resolver.openTypedAssetFileDescriptor(uri, openableMimeTypes[0], null).createInputStream();
}