一、前言

Android 4.4（API級別19）引入了存儲訪問框架（SAF）。
通過SAF，用戶可以輕松地瀏覽和打開所有首選文檔存儲提供商中的文檔，圖像和其他文件。
也就是說，接下來介紹的方式適用于android4.4+的操作系統。
參考鏈接：https://developer.android.com/guide/topics/providers/document-provider

二、詳細實現

1、調出系統文件管理器界面

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除了可以設置為ACTION_OPEN_DOCUMEN，還可以替換為ACTION_GET_CONTENT ，兩者的區別如下：

• 如果您希望您的應用僅讀取/導入數據，請使用ACTION_GET_CONTENT。 通過這種方法，應用程序可以導入數據的副本，例如圖像文件。
• 如果希望您的應用對文件提供者擁有的文件具有長期，持久的訪問權限，請使用ACTION_OPEN_DOCUMENT。

2）Category設置為CATEGORY_OPENABLE，過濾出可以打開的文件

3）Type設置的是MIMETYPE,比如:

• 過濾所有圖片，則設置為："image/*"
• 只過濾png圖片，則設置為："image/png"
• 過濾apk，那么可設置為："application/vnd.android.package-archive"

4）startActivityForResult 啟動Inetent,以便在onActivityResult接收文件選擇結果

2、在onActivityResult中處理返回結果

@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）從Intent中getData()獲取到返回的Uri對象，舊版本是file://開頭，新版本是content://開頭

3、從Uri獲取所需的信息

1）從Uri中獲取文件元數據，一般只能獲取到文件名與大小

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）將Uri轉換為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)將Uri轉換為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 常見的用法：

文件類型mime名稱文件類型mime名稱

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、文件創建、編輯與刪除

1、創建文件，可以在onActivity中接收到結果

// 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、獲取Uri之后，要是文件的Document.COLUMN_FLAGS 包含SUPPORTS_DELETE，則可以刪除該文件：

DocumentsContract.deleteDocument(getContentResolver(), uri);

3、編輯文件

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、檢查最新的文件數據

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在存儲訪問框架中添加了虛擬文件的概念。
2、即使虛擬文件沒有二進制表示形式，您的客戶端應用程序也可以通過將其強制轉換為其他文件類型或使用ACTION_VIEW意圖查看這些文件來打開其內容。
3、要打開虛擬文件，您的客戶端應用程序需要包含特殊的邏輯來處理它們。如果要獲取文件的字節表示形式（例如，預覽文件），則需要從文檔提供者處請求其他MIME類型。
4、要在您的應用程序中獲取虛擬文檔的URI，首先要創建一個Intent以打開文件選擇器UI，就像前面在Seach中為文檔顯示的代碼一樣。
5、重要提示：由于應用無法使用openInputStream（）方法直接打開虛擬文件，因此，如果您在ACTION_OPEN_DOCUMENT意向中包括CATEGORY_OPENABLE類別，則您的應用將不會收到任何虛擬文件。用戶做出選擇后，系統將調用onActivityResult（）方法，如先前在處理結果中所示。您的應用可以檢索文件的URI，然后使用類似于以下代碼片段的方法來確定文件是否為虛擬文件。驗證文件為虛擬文件后，可以將其強制轉換為其他MIME類型，例如圖像文件。以下代碼段顯示了如何檢查虛擬文件是否可以表示為映像，如果可以，則從虛擬文件獲取輸入流。

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(); }

總結

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