¿Cómo crear un archivo en Android?

Question

¿Cómo crear un archivo, escribir datos en él y leer datos desde él en Android? Si es posible, proporcione un fragmento de código.

Answer 1

From here: http://www.anddev.org/working_with_files-t115.html

//Writing a file... 



try { 
     // catches IOException below 
     final String TESTSTRING = new String("Hello Android"); 

     /* We have to use the openFileOutput()-method 
     * the ActivityContext provides, to 
     * protect your file from others and 
     * This is done for security-reasons. 
     * We chose MODE_WORLD_READABLE, because 
     * we have nothing to hide in our file */    
     FileOutputStream fOut = openFileOutput("samplefile.txt", 
                  MODE_PRIVATE); 
     OutputStreamWriter osw = new OutputStreamWriter(fOut); 

     // Write the string to the file 
     osw.write(TESTSTRING); 

     /* ensure that everything is 
     * really written out and close */ 
     osw.flush(); 
     osw.close(); 

//Reading the file back... 

     /* We have to use the openFileInput()-method 
     * the ActivityContext provides. 
     * Again for security reasons with 
     * openFileInput(...) */ 

     FileInputStream fIn = openFileInput("samplefile.txt"); 
     InputStreamReader isr = new InputStreamReader(fIn); 

     /* Prepare a char-Array that will 
     * hold the chars we read back in. */ 
     char[] inputBuffer = new char[TESTSTRING.length()]; 

     // Fill the Buffer with data from the file 
     isr.read(inputBuffer); 

     // Transform the chars to a String 
     String readString = new String(inputBuffer); 

     // Check if we read back the same chars that we had written out 
     boolean isTheSame = TESTSTRING.equals(readString); 

     Log.i("File Reading stuff", "success = " + isTheSame); 

    } catch (IOException ioe) 
     {ioe.printStackTrace();} 

Answer 2

que utiliza el código siguiente para crear un archivo temporal para la escritura de bytes. Y está funcionando bien.

File file = new File(Environment.getExternalStorageDirectory() + File.separator + "test.txt"); 
file.createNewFile(); 
byte[] data1={1,1,0,0}; 
//write the bytes in file 
if(file.exists()) 
{ 
    OutputStream fo = new FileOutputStream(file);    
    fo.write(data1); 
    fo.close(); 
    System.out.println("file created: "+file); 
    url = upload.upload(file); 
}    

//deleting the file    
file.delete(); 
System.out.println("file deleted"); 

Answer 3

Decidí escribir una clase de este hilo que puede ser útil para otros. Tenga en cuenta que esto está pensado actualmente para escribir en el directorio "archivos" solamente (por ejemplo, no escribe en las rutas de "tarjeta SD").

import java.io.BufferedReader; 
import java.io.FileInputStream; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.io.OutputStreamWriter; 

import android.content.Context; 

public class AndroidFileFunctions { 

    public static String getFileValue(String fileName, Context context) { 
     try { 
      StringBuffer outStringBuf = new StringBuffer(); 
      String inputLine = ""; 
      /* 
      * We have to use the openFileInput()-method the ActivityContext 
      * provides. Again for security reasons with openFileInput(...) 
      */ 
      FileInputStream fIn = context.openFileInput(fileName); 
      InputStreamReader isr = new InputStreamReader(fIn); 
      BufferedReader inBuff = new BufferedReader(isr); 
      while ((inputLine = inBuff.readLine()) != null) { 
       outStringBuf.append(inputLine); 
       outStringBuf.append("\n"); 
      } 
      inBuff.close(); 
      return outStringBuf.toString(); 
     } catch (IOException e) { 
      return null; 
     } 
    } 

    public static boolean appendFileValue(String fileName, String value, 
      Context context) { 
     return writeToFile(fileName, value, context, Context.MODE_APPEND); 
    } 

    public static boolean setFileValue(String fileName, String value, 
      Context context) { 
     return writeToFile(fileName, value, context, 
       Context.MODE_WORLD_READABLE); 
    } 

    public static boolean writeToFile(String fileName, String value, 
      Context context, int writeOrAppendMode) { 
     // just make sure it's one of the modes we support 
     if (writeOrAppendMode != Context.MODE_WORLD_READABLE 
       && writeOrAppendMode != Context.MODE_WORLD_WRITEABLE 
       && writeOrAppendMode != Context.MODE_APPEND) { 
      return false; 
     } 
     try { 
      /* 
      * We have to use the openFileOutput()-method the ActivityContext 
      * provides, to protect your file from others and This is done for 
      * security-reasons. We chose MODE_WORLD_READABLE, because we have 
      * nothing to hide in our file 
      */ 
      FileOutputStream fOut = context.openFileOutput(fileName, 
        writeOrAppendMode); 
      OutputStreamWriter osw = new OutputStreamWriter(fOut); 
      // Write the string to the file 
      osw.write(value); 
      // save and close 
      osw.flush(); 
      osw.close(); 
     } catch (IOException e) { 
      return false; 
     } 
     return true; 
    } 

    public static void deleteFile(String fileName, Context context) { 
     context.deleteFile(fileName); 
    } 
} 

Answer 4

escribir en un archivo test.txt:

String filepath ="/mnt/sdcard/test.txt"; 
FileOutputStream fos = null; 
try { 
     fos = new FileOutputStream(filepath); 
     byte[] buffer = "This will be writtent in test.txt".getBytes(); 
     fos.write(buffer, 0, buffer.length); 
     fos.close(); 
    } catch (FileNotFoundException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    }finally{ 
     if(fos != null) 
      fos.close(); 
    } 

Leer del archivo test.txt:

String filepath ="/mnt/sdcard/test.txt";   
FileInputStream fis = null; 
try { 
     fis = new FileInputStream(filepath); 
     int length = (int) new File(filepath).length(); 
     byte[] buffer = new byte[length]; 
     fis.read(buffer, 0, length); 
     fis.close(); 
    } catch (FileNotFoundException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    }finally{ 
     if(fis != null) 
      fis.close(); 
    } 

Nota: no se olvide de añadir estos dos permisos en AndroidManifest. xml

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