Android app writes data to internal storage and external storage sample _android

File storage (internal storage)
once the program is installed in the device, the data/data/package name/That is the internal storage space, external confidentiality.
The context provides 2 ways to open an input, output stream

• FileInputStream openfileinput (String name)
• FileOutputStream openfileoutput (String name, int mode)

public class Mainactivity extends activity {private TextView show;
  Private EditText et;
  Private String filename = "Test";
    @Override protected void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate);
    Setcontentview (R.layout.activity_main);
    Show = (TextView) Findviewbyid (r.id.show);

    ET = (edittext) Findviewbyid (r.id.et);  Findviewbyid (R.id.write). Setonclicklistener (New View.onclicklistener () {@Override public void OnClick (View v)
          {try {FileOutputStream fos = openfileoutput (filename, context.mode_private); FileOutputStream is a byte stream, if it is written text, the need to further FileOutputStream packaging UTF-8 is encoded outputstreamwriter OSW = new Outputstreamwrite
          R (Fos, "UTF-8");
          Write Osw.write (Et.gettext (). toString ());
          Osw.flush ();
          Fos.flush ();
          Osw.close ();
        Fos.close ();
        catch (FileNotFoundException e) {e.printstacktrace (); catch (UnsupporteDencodingexception e) {//TODO auto-generated catch block E.printstacktrace ();
        catch (IOException e) {//TODO auto-generated catch block E.printstacktrace ();  

    }
      }
    }); Findviewbyid (R.id.read). Setonclicklistener (New View.onclicklistener () {@Override public void OnClick (View v)
          {try {FileInputStream FIS = openfileinput (filename);
          When the input and output are specified character set encoding, there will be no garbled situation inputstreamreader ISR = new InputStreamReader (FIS, "UTF-8");
          Gets the available length of the file, constructs a character array char[] input = new char[fis.available ()];
          Isr.read (input);
          Isr.close ();
          Fis.close ();
          String readed = new string (input);
        Show.settext (readed);
        catch (FileNotFoundException e) {e.printstacktrace ();
        catch (Unsupportedencodingexception e) {//TODO auto-generated catch block E.printstacktrace (); Catch(IOException e)
        {//TODO auto-generated catch block E.printstacktrace ();      
  }
      }
    });

 }  
}

Data/data/packagename/files/test is the file we write.

SD storage (External storage)
The Mnt/sdcard directory is the mount point of the SD card (just a point).
Storage/sdcard: The real SD card operation directory.

First, File download
Android Development, sometimes need to download some resources from the Internet for users to use, the Android API has provided a lot of directly available classes for everyone to use, general file download requires three steps:
1. Create a HttpURLConnection object

Creates a URL object that contains an IP address, urlstr refers to the network IP address 
url = new URL (urlstr); 
Create a HttpURLConnection object through the URL object
httpurlconnection urlconn = (httpurlconnection) url.openconnection ();

2. Get a InputStream object

InputStream input = Urlconn.getinputstream ();

3. Set permissions to access the network

Add permission information to the Androidmanifest.xml configuration file 
<uses-permission android:name= "Android.permission.INTERNET"/>

Second, access and write SD card
1. To determine whether the cell phone inserted SD card, and the application has read and write permissions

Environment.getexternalstoragestate (). Equals (environment.media_mounted);

2. Get the current SD card directory

Environment.getexternalstoragedirectory ();

3. You must also set permissions in the configuration file before accessing the SD card so that you can access the most SD card

<uses-permission android:name= "Android.permission.WRITE_EXTERNAL_STORAGE"/>

The following is a commonly used in the SD operation of the encapsulation class, if the need for the SD card operation, directly can be brought over with

public class FileUtils {private String sdpath;
  Public String Getsdpath () {return sdpath; }//constructor, get the directory of SD card, this line function gets the directory name is actually called "/sdcard" public FileUtils () {Sdpath = Environment.getexternalstoragedirectory ()
  +"/"; ///create file on SD card public file Createsdfile (String fileName) throws ioexception{file = new file (Sdpath + fileName
    );
    File.createnewfile ();
  return file;
    ///Create directory Public File createsddir (String dirname) {file dir = new file (Sdpath + dirname) on SD card;
    Dir.mkdir ();
  return dir;
    //Determine if the folder on the SD card exists public boolean isfileexist (String fileName) {File File = new file (Sdpath + fileName);
  return file.exists (); ///write the data in a InputStream to the SD card//write the input to the filename file in the directory of path, public file Write2sdfrominput (string path, String fi 
    Lename, InputStream Input) {file file = null; 
    OutputStream output = null; 
      try{createsddir (path); 
      File = createsdfile (path + fileName); FileInputStream is reading data, FileoUtputstream is written to data, written to file to output = new FileOutputStream (files); 
      byte buffer [] = new byte[4 * 1024]; 
      while ((Input.read (buffer))!=-1) {output.write (buffer); 
    } output.flush (); 
    catch (Exception e) {e.printstacktrace (); 
      } finally{try{output.close (); 
      catch (Exception e) {e.printstacktrace (); 
  } return file;
 } 
}