SD Card Operation "Android 8"

Read/write SD card

The Openfileinput and Openfileoutput methods of the context class are file operations for the application's Data folder, which has some limitations due to the limited ROM capacity of the phone.

The SD card of the phone provides a larger storage capacity than the ROM. More suitable for accessing large files.

environment[Android.os. Environment]

Constants and methods	Type	Describe
public static final String media_mounted	Constant	Extended storage set allows read and write access
public static final String media_checking	Constant	Extended storage set in check state
public static final String media_mounted_read_only	Constant	Extended storage set in read-only state
public static final String media_removed	Constant	Extended storage setting does not exist
public static final String media_unmounted	Constant	The extended storage setting was not found
public static File Getdatadirectory ()	Ordinary	Get the Data Directory
public static File Getdownloadcachedirectory ()	Ordinary	Get the downloaded cache directory
public static File getExternalStorageDirectory ()	Ordinary	Get the Extended storage directory
public static String Getexternalstoragestate ()	Ordinary	Get the status of an extended storage device
public static File Getrootdirectory ()	Ordinary	Get root directory
public static Boolean isexternalstorageremovable ()	Ordinary	Determine if the extended storage directory is deleted

Request read and write access to the SD card

Open the project manifest file and select Permissions in the Permission tab

SD card File read operation

1 PrivateTextView TV; 2 PrivateButton bt1;3 PrivateButton BT2; 4 PrivateEditText et;5 6 protected voidonCreate (Bundle savedinstancestate) {7         Super. OnCreate (savedinstancestate);8 Setcontentview (r.layout.xml file);9ET =(EditText) Findviewbyid (r.id.sdet);TenTV =(TextView) Findviewbyid (R.ID.SDTV); OneBT1 =(Button) Findviewbyid (r.id.sdbt01); ABT2 =(Button) Findviewbyid (r.id.sdbt02); -Bt1.setonclicklistener ( This); -Bt2.setonclicklistener ( This); the     } -  -  Public voidOnClick (View v) { -         if(!environment.getexternalstoragestate (). Equals ( +environment.media_mounted)) {//determine if the SD card exists -Toast.maketext (Sd0. This, "SD card does not exist", 3000). Show (); +             return; A         } at         Switch(V.getid ()) { -          Caser.id.sdbt01: -             //Create a Folder object -File dir =NewFile (Environment.getexternalstoragedirectory (), "test"); -             if(!dir.exists ()) {//If the directory does not exist, create - Dir.mkdir (); in             } -File File =NewFile (dir, "test.txt");//Create a file to PrintWriter PW; +             Try { -PW =Newprintwriter (file); the pw.println (Et.gettext (). toString ()); * pw.close (); $Toast.maketext (Sd0. This, "saved successfully", 3000). Show ();Panax Notoginseng}Catch(FileNotFoundException e) { - e.printstacktrace (); the             } +              Break; A          Caser.id.sdbt02: theFile f =NewFile (environment.getexternalstoragedirectory () + +"/test/test.txt");//Create a Folder object - bufferedreader BR; $             Try { $BR =NewBufferedReader (NewInputStreamReader (NewFileInputStream (f))); -String str =NULL; -                  while(str = br.readline ())! =NULL) { the tv.append (str); -                 }Wuyi}Catch(FileNotFoundException e) { the e.printstacktrace (); -}Catch(IOException e) { Wu e.printstacktrace (); -             } About              Break; $         } -}

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SD Card Operation "Android 8"