외부 저장소에 파일을 쓰거나 읽을 수 없습니다. - Android

Question

외부 저장소에 파일을 쓰고 읽는 간단한 프로그램을 작성하려고합니다. 다음은 문제에 대한 설명입니다.
1. 텍스트 "hello world"가 포함 된 파일 이름 = "hello_files.txt"는 /sdcard에 저장됩니다.
2. 파일에 대한 데이터가 작성되면 파일은 adb으로 볼 수 있습니다.
3. 그러나 응용 프로그램을 휴대 전화에로드하고 타사 파일 탐색기 응용 프로그램을 사용하여 보았 으면 hello_files.txt 파일에 텍스트가 기록되지 않은 것으로 보입니다. 내 프로그램의 일부를 쓰지 만, 나는 무엇을 알아낼 수 없다. 나는 코드의 두 부분 아래에 글쓰기와 읽기 모두를 주었다.

파일에서 읽기위한 코드 :

public void readFromFile() { 

      //Step 1. Check if the storage is available. 
      boolean mStorageAvailable; 
      boolean mStorageReadWrite; 

      String state = Environment.MEDIA_MOUNTED; 
      Log.v(this.toString(), "State of media = " + state); 

      if(Environment.MEDIA_MOUNTED.equals(state)) { 
       Log.v(this.toString(), "Media is mounted."); 
       mStorageAvailable = true; 
       mStorageReadWrite = true; 

       File dir = Environment.getExternalStorageDirectory(); 
       String fileName = dir + "/" + file; 
       Log.v(this.toString(), "Reading from file = " + fileName); 

       File f = new File(dir, file); 

       FileReader fr = null; 
       try { 
        fr = new FileReader(f); 
        Log.v(this.toString(), "Wrapping a buffered reader around file reader."); 
        BufferedReader bufRead = new BufferedReader(fr, 8192); 
        //Log.v(this.toString(), bufRead.toString()); 
        String line; 
        try { 
         line = bufRead.readLine(); 
         Log.v(this.toString(), "Line read = " + line); 
         Toast.makeText(getApplicationContext(), line, Toast.LENGTH_SHORT).show(); 
        } catch (IOException e) { 
         // TODO Auto-generated catch block 
         e.printStackTrace(); 
         Log.v(this.toString(), "IOException found in reading line from file."); 
        } 
       } catch (FileNotFoundException e1) { 
        // TODO Auto-generated catch block 
        e1.printStackTrace(); 
        Log.v(this.toString(), "File not found for reading."); 
       } 
      } 
} 

파일로 작성하기위한 코드는 다음과 같습니다

public void writeToFile() { 

     //Step 2. Check if external storage is mounted. 
     boolean mStorageExists; 
     boolean mStorageReadWrite; 

     String state = Environment.getExternalStorageState(); 
     Log.v(this.toString(), "External media mounted state = " + state); 

     if(Environment.MEDIA_MOUNTED.equals(state)) { 
      //media is mounted. 
      //Mounted storage is read/write. 
      //Write to the file. 

      mStorageExists = true; 
      mStorageReadWrite = true; 

      Log.v(this.toString(), "Going to write to a file."); 

      //get directory. 
      File dir = Environment.getExternalStorageDirectory(); 
      Log.v(this.toString(), "Root directory = " + dir.getAbsolutePath()); 
      String fileName = dir.getAbsolutePath() + "/" + file; 

      Log.v(this.toString(), "File to write to is present at " + fileName); 

      File f = new File(dir, file); 

      FileOutputStream fos; 
      try { 
       fos = new FileOutputStream(f); 
      } catch (FileNotFoundException e1) { 
       // TODO Auto-generated catch block 
       e1.printStackTrace(); 
       Log.v(this.toString(), "File not found."); 
      } 
      try { 
       fos = openFileOutput(file, MODE_WORLD_READABLE | MODE_WORLD_WRITEABLE); 
       Log.v(this.toString(), "Bytes of the string = " + str.getBytes().toString()); 
       fos.write(str.getBytes()); 
       //Log.v(this.toString(), "Local path = "); 
       fos.close(); 
      } catch (FileNotFoundException e) { 
       // TODO Auto-generated catch block 
       Log.v(this.toString(), "File not found!!"); 
       e.printStackTrace(); 
      } catch (IOException e) { 
       Log.v(this.toString(), "IO Exception."); 
       e.printStackTrace(); 
      } 
     } else if(Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { 
      //media is mounted but read only. 
      mStorageExists = true; 
      mStorageReadWrite = false; 
      Log.v(this.toString(), "The media is read-only mounted."); 
     } else if((Environment.MEDIA_NOFS.equals(state)) || (Environment.MEDIA_REMOVED.equals(state)) || (Environment.MEDIA_UNMOUNTED.equals(state))) { 
      mStorageExists = false; 
      mStorageReadWrite = false; 
      Log.v(this.toString(), "There is some problem with the media."); 
     } 
    } 

합니다 (Log 자세한 태그에서) 로그 :

10-23 10:26:19.444: V/com.sriram.fileops.MainActivity$2@44e95cc0(466): Read from file button clicked. 
10-23 10:26:19.444: V/com.sriram.fileops.MainActivity@44e90428(466): State of media = mounted 
10-23 10:26:19.444: V/com.sriram.fileops.MainActivity@44e90428(466): Media is mounted. 
10-23 10:26:19.444: V/com.sriram.fileops.MainActivity@44e90428(466): Reading from file = /sdcard/hello_files.txt 
10-23 10:26:19.453: V/com.sriram.fileops.MainActivity@44e90428(466): Wrapping a buffered reader around file reader. 
10-23 10:26:19.453: V/com.sriram.fileops.MainActivity@44e90428(466): Line read = null 

Answer 1

외부 저장소에 대한 액세스 권한을 포함하는 것 외에도 다음과 같은 writin 함수 g 작업과 파일 읽기 작업.

public void writeToFile() { 

     //Step 2. Check if external storage is mounted. 
     boolean mStorageExists; 
     boolean mStorageReadWrite; 

     String state = Environment.getExternalStorageState(); 
     Log.v(this.toString(), "External media mounted state = " + state); 

     if(Environment.MEDIA_MOUNTED.equals(state)) { 
      //media is mounted. 
      //Mounted storage is read/write. 
      //Write to the file. 

      mStorageExists = true; 
      mStorageReadWrite = true; 

      Log.v(this.toString(), "Going to write to a file."); 

      //get directory. 
      File dir = Environment.getExternalStorageDirectory(); 
      Log.v(this.toString(), "Root directory = " + dir.getAbsolutePath()); 

      String file_to_write = getFileToWrite(dir); //this returns the exact name of the file. 

      String fileName = dir.getAbsolutePath() + "/" + file_to_write; 

      Log.v(this.toString(), "File to write to is present at " + file_to_write); 

      File f = new File(dir, file_to_write); 
      FileWriter fw = null; 
      try { 
       fw = new FileWriter(f); 
       fw.write(str); 
       fw.close(); 
      } catch (IOException e2) { 
       // TODO Auto-generated catch block 
       Log.v(this.toString(), "IOException caught in initializing filewriter."); 
       e2.printStackTrace(); 
      } 
     } else if(Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { 
      //media is mounted but read only. 
      mStorageExists = true; 
      mStorageReadWrite = false; 
      Log.v(this.toString(), "The media is read-only mounted."); 
     } else if((Environment.MEDIA_NOFS.equals(state)) || (Environment.MEDIA_REMOVED.equals(state)) || (Environment.MEDIA_UNMOUNTED.equals(state))) { 
      mStorageExists = false; 
      mStorageReadWrite = false; 
      Log.v(this.toString(), "There is some problem with the media."); 
     } 
    } 

및 파일 읽기 기능 :

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

쓰기 파일로

public void readFromFile() { 

     //Step 1. Check if the storage is available. 
     boolean mStorageAvailable; 
     boolean mStorageReadWrite; 

     String state = Environment.MEDIA_MOUNTED; 
     Log.v(this.toString(), "State of media = " + state); 

     if(Environment.MEDIA_MOUNTED.equals(state)) { 
      Log.v(this.toString(), "Media is mounted."); 
      mStorageAvailable = true; 
      mStorageReadWrite = true; 

      File dir = Environment.getExternalStorageDirectory(); 
      String file_to_read_from = getFileToRead(dir); 
      String fileName = dir + "/" + file_to_read_from; 
      Log.v(this.toString(), "Reading from file = " + fileName); 

      File f = new File(dir, file_to_read_from); 
      //Log.v(this.toString(), "Read from file = " + f.canRead() + " " + f.isFile() + " " + f.exists() + " " + f.length() + " " + f.lastModified()); 

      try { 
       FileReader fis = new FileReader(f); 
       Log.v(this.toString(), "Wrapping a buffered reader around file reader."); 
       BufferedReader bufRead = new BufferedReader(fis, 100); 
       String line; 
       try { 
        line = bufRead.readLine(); 
        Toast.makeText(getApplicationContext(), line, Toast.LENGTH_SHORT).show(); 
        Log.v(this.toString(), "Line read = " + line); 
        while(line != null) { 
         Log.v(this.toString(), "Line read = " + line); 
         Toast.makeText(getApplicationContext(), line, Toast.LENGTH_SHORT).show(); 
         line = bufRead.readLine(); 
        } 
       } catch (IOException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
        Log.v(this.toString(), "IOException found in reading line from file."); 
       } 
      } catch (FileNotFoundException e1) { 
       // TODO Auto-generated catch block 
       e1.printStackTrace(); 
       Log.v(this.toString(), "File not found for reading."); 
      } 
     } 
    }