"Go" Android sdcard operation (file read/write, capacity calculation)

Android.os.Environment

Provides access to environment variables

Java.lang.Object
	Android.os.Environment

Environment static method:

Method: Getdatadirectory ()

return: File

Explanation: Returns the directory of data

Method: Getdownloadcachedirectory ()

return: File

Explanation: Return to download buffer directory

Method: getExternalStorageDirectory ()

return: File

Explanation: Returning an extended storage directory (SDcard)

Method: getexternalstoragepublicdirectory (String type)

return: File

Explanation: Return a high-end public external memory directory to place certain types of files (from the web)

Method: Getrootdirectory ()

return: File

Explanation: Return to Android root directory

Method: Getexternalstoragestate ()

Returns: String

Explanation: Returns the current state of an external storage device

Getexternalstoragestate () returns the status of the string type constant:

Constant: Media_bad_removal

Value: "Bad_removal"

Explanation: Removed before SDcard was properly uninstalled

Constant: media_checking

Value: "Checking"

Explanation: Disk check is in progress

Constant: media_mounted

Value: "Mounted"

Explanation: is already mounted and has a readable writable permission

Constant: Media_mounted_read_only

Value: "Mounted_ro"

Explanation: already mounted, but with only readable permissions

Constant: Media_nofs

Value: "Nofs"

Explanation: The object is blank, or the file system does not support

Constant: media_removed

Value: "Removed"

Explanation: The extension device has been removed

Constant: media_shared

Value: "Shared"

Explanation: If SDcard is not mounted and shared via USB mass storage

Constant: media_unmountable

Value: "Unmountable"

Explanation: Can not mount any expansion device

Constant: media_unmounted

Value: "Unmounted"

Explanation: Already uninstalled

When using, just first determine the current state of SDcard and then get the SDcard directory (see source code)

---------------------------------------------------------------------------------------------------------

2. SDcard operation
4. Ublic void Sdcardtest () {
6. Get extended SD card Device status
8. String sdstatestring = Android.os.Environment.getExternalStorageState ();
12. Have readable writable permissions
14. if (Sdstatestring.equals (Android.os.Environment.MEDIA_MOUNTED)) {
18. try {
22. //Get the file directory for the extended storage device
24. File Sdfile = android.os.Environment
26. . getExternalStorageDirectory ();
30. //Open File
32. File MyFile = new File (Sdfile.getabsolutepath ()
34. + File.separator + "MyFile.txt");
38. //Determine if it exists, does not exist then creates
40. if (!myfile.exists ()) {
42. Myfile.createnewfile ();
44. }
48. //Write Data
50. String Szouttext = "Hello, world!";
52. FileOutputStream outputstream = new FileOutputStream (MyFile);
54. Outputstream.write (Szouttext.getbytes ());
56. Outputstream.close ();
60. } catch (Exception e) {
62. //Todo:handle exception
64. }//end of Try
68. }//End of If (media_mounted)
70. Have read-only permissions
72. else if (sdstatestring
74. . EndsWith (Android.os.Environment.MEDIA_MOUNTED_READ_ONLY)) {
78. //Get the file directory for the extended storage device
80. File sdfile = Android.os.Environment.getExternalStorageDirectory ();
84. //Create a file
86. File MyFile = new File (Sdfile.getabsolutepath () + File.separator
88. + "MyFile.txt");
92. //Determine if the file exists
94. if (myfile.exists ()) {
96. try {
100. //Read Data
102. FileInputStream InputStream = new FileInputStream (MyFile);
104. byte[] buffer = new byte[1024];
106. Inputstream.read (buffer);
108. Inputstream.close ();
112. } catch (Exception e) {
114. //Todo:handle exception
116. }//end of Try
118. }//End of If (MyFile)
120. }//End of If (media_mounted_read_only)
122. End of Func

Calculates the capacity size of the SDcard android.os.StatFs

A class that simulates the DF command of Linux to get the use of SD card and phone memory

Java.lang.Object
	Android.os.StatFs

Construction Method:

StatFs (String Path)

Common methods:

Method: Getavailableblocks ()

return: int

Explanation: Returns the remaining blocks on the file system that can be used by the program

Method: Getblockcount ()

return: int

Explanation: Returns a total of blocks on the file system

Method: Getblocksize ()

return: int

Explanation: Returns the size unit of a block of file system byte

Method: Getfreeblocks ()

return: int

Explanation: All remaining blocks on the file system are returned, including reservations that are not accessible by the general program

Method: REStat (String path)

return: void

Explanation: Executes a file system Restat that is referenced by the object. (Google Translate)

To calculate the size and usage of the sdcard, you only need to get the total number of blocks that the SD card has, or the number of blocks left unused, multiplied by the size of each block is the corresponding capacity size of the unit byte. (See Code)

2. public void Sdcardsizetest () {
6. Get the current state of SDcard
8. String sdcstring = Android.os.Environment.getExternalStorageState ();
12. if (Sdcstring.equals (Android.os.Environment.MEDIA_MOUNTED)) {
16. //Get sdcard file path
18. File Pathfile = android.os.Environment
20. . getExternalStorageDirectory ();
24. Android.os.StatFs StatFs = new Android.os.StatFs (Pathfile.getpath ());
28. //Get total block on SDcard
30. Long ntotalblocks = Statfs.getblockcount ();
34. //Get the size of each block on the SDcard
36. Long nblocsize = Statfs.getblocksize ();
40. //Get the number of blocks available for the program to use
42. Long Navailablock = Statfs.getavailableblocks ();
46. //Get the number of all remaining blocks (including block that is not available for General program reservation)
48. Long Nfreeblock = Statfs.getfreeblocks ();
52. //Calculate SDcard Total capacity MB
54. Long nsdtotalsize = ntotalblocks * Nblocsize/ 1024x768/ 1024;
58. //Calculate sdcard remaining size MB
60. Long nsdfreesize = Navailablock * Nblocsize/ 1024x768/ 1024;
62. }//end of If
64. End of Func

Reprinted from: http://crackren.javaeye.com/blog/747121

"Go" Android sdcard operation (file read/write, capacity calculation)