Android scrittura alla cartella della scheda SD

Question

Sto usando il seguente codice per scaricare un file dal mio server quindi scrivere nella directory principale della scheda SD, tutto funziona bene:

package com.downloader; 

import java.io.File; 
import java.io.FileOutputStream; 
import java.io.InputStream; 
import java.net.HttpURLConnection; 
import java.net.URL; 

import android.os.Environment; 
import android.util.Log; 

public class Downloader { 

    public void DownloadFile(String fileURL, String fileName) { 
     try { 
      File root = Environment.getExternalStorageDirectory(); 
      URL u = new URL(fileURL); 
      HttpURLConnection c = (HttpURLConnection) u.openConnection(); 
      c.setRequestMethod("GET"); 
      c.setDoOutput(true); 
      c.connect(); 
      FileOutputStream f = new FileOutputStream(new File(root, fileName)); 

      InputStream in = c.getInputStream(); 

      byte[] buffer = new byte[1024]; 
      int len1 = 0; 
      while ((len1 = in.read(buffer)) > 0) { 
       f.write(buffer, 0, len1); 
      } 
      f.close(); 
     } catch (Exception e) { 
      Log.d("Downloader", e.getMessage()); 
     } 

    } 
} 

Tuttavia, utilizzando Environment.getExternalStorageDirectory(); significa che il file scriverà sempre alla radice /mnt/sdcard. È possibile specificare una determinata cartella in cui scrivere il file?

Ad esempio: /mnt/sdcard/myapp/downloads

Acclamazioni

Eef

Answer 1

File sdCard = Environment.getExternalStorageDirectory(); 
File dir = new File (sdCard.getAbsolutePath() + "/dir1/dir2"); 
dir.mkdirs(); 
File file = new File(dir, "filename"); 

FileOutputStream f = new FileOutputStream(file); 
... 

Answer 2

Aggiungi Permesso di Android Manifest

Aggiungi this WRITE_EXTERNAL_STORAGE permission alle vostre applicazioni manifeste.

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="your.company.package" 
    android:versionCode="1" 
    android:versionName="0.1"> 
    <application android:icon="@drawable/icon" android:label="@string/app_name"> 
     <!-- ... --> 
    </application> 
    <uses-sdk android:minSdkVersion="7" /> 
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> 
</manifest> 

Verifica la disponibilità di storage esterno

Si dovrebbe sempre verificare la disponibilità prima. Un frammento di codice da the official android documentation on external storage.

boolean mExternalStorageAvailable = false; 
boolean mExternalStorageWriteable = false; 
String state = Environment.getExternalStorageState(); 

if (Environment.MEDIA_MOUNTED.equals(state)) { 
    // We can read and write the media 
    mExternalStorageAvailable = mExternalStorageWriteable = true; 
} else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { 
    // We can only read the media 
    mExternalStorageAvailable = true; 
    mExternalStorageWriteable = false; 
} else { 
    // Something else is wrong. It may be one of many other states, but all we need 
    // to know is we can neither read nor write 
    mExternalStorageAvailable = mExternalStorageWriteable = false; 
} 

Utilizzare un FileWriter

In ultimo, ma non meno importante dimenticare il FileOutputStream e utilizzare un FileWriter invece. Ulteriori informazioni su quel modulo di classe the FileWriter javadoc. Potresti voler aggiungere qualche altra gestione degli errori qui per informare l'utente.

// get external storage file reference 
FileWriter writer = new FileWriter(getExternalStorageDirectory()); 
// Writes the content to the file 
writer.write("This\n is\n an\n example\n"); 
writer.flush(); 
writer.close(); 

Answer 3

trovato la risposta qui - http://mytechead.wordpress.com/2014/01/30/android-create-a-file-and-write-to-external-storage/

Dice,

/** 

* Method to check if user has permissions to write on external storage or not 

*/ 

public static boolean canWriteOnExternalStorage() { 
    // get the state of your external storage 
    String state = Environment.getExternalStorageState(); 
    if (Environment.MEDIA_MOUNTED.equals(state)) { 
    // if storage is mounted return true 
     Log.v("sTag", "Yes, can write to external storage."); 
     return true; 
    } 
    return false; 
} 

e quindi cerchiamo di utilizzare questo codice per scrivere in realtà per l'archiviazione esterna:

// get the path to sdcard 
File sdcard = Environment.getExternalStorageDirectory(); 
// to this path add a new directory path 
File dir = new File(sdcard.getAbsolutePath() + "/your-dir-name/"); 
// create this directory if not already created 
dir.mkdir(); 
// create the file in which we will write the contents 
File file = new File(dir, "My-File-Name.txt"); 
FileOutputStream os = outStream = new FileOutputStream(file); 
String data = "This is the content of my file"; 
os.write(data.getBytes()); 
os.close(); 

E questo è. Se ora visiti la tua/sdcard/nome-dir-nome/cartella vedrai un file chiamato - My-File-Name.txt con il contenuto come specificato nel codice.

PS: - sono necessari i seguenti permessi -

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

Answer 4

Per scaricare un file da scaricare o cartella della musica SDCard

File downlodDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);// or DIRECTORY_PICTURES 

E non dimenticate di aggiungere questi autorizzazione manifest

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