FileNotFoundException при чтении из FileInputStream

Question

Я пытаюсь этот код:

http://androidgenuine.com/?tag=export-database-android

Используя этот код в моем примере, я всегда получаю FileNotFoundException, хотя папка существует во внешнем время хранения чтение FileInputStream.

Вот мой код:

public void exportdata() 
    { 

     try 
     { 

      myInput = new FileInputStream("/data/data/com.example.hello/databases/BikeMaintenance.db"); 
      File directory = new File("/sdcard/BikeMaintenance/Data/"); 
      // Create the folder if it doesn't exist: 
      if (!directory.exists()) 
      { 
       directory.mkdirs(); 
      } 

      OutputStream myOutput = new FileOutputStream(directory.getPath()+"/BikeMaintenance.backup"); 
      byte[] buffer = new byte[1024]; 
      int length; 
      while ((length = myInput.read(buffer))>0) 
      { 

       myOutput.write(buffer, 0, length); 
       msg="Backup Succesfull!"; 
       Toast.makeText(MainPage.this,msg,Toast.LENGTH_SHORT).show(); 
      } 
      // Close and clear the streams 
      myOutput.flush(); 
      myOutput.close();   
      myInput.close(); 
     } 
     catch (FileNotFoundException e) 
     { 
      msg="FileNotFoundException"; 
      Toast.makeText(MainPage.this,msg,Toast.LENGTH_SHORT).show(); 

      e.printStackTrace(); 
     } 
     catch (IOException e) 
     { 
      msg="Backup Unsuccesfull!"; 
      Toast.makeText(MainPage.this,msg,Toast.LENGTH_SHORT).show(); 
     } 

    } 

Где я буду неправильно? Что может быть причиной этого? Я искал решение для этого, но не нашел решения.

Вот выход LogCat:

 
java.io.FileNotFoundException: 
/data/data/com.example.hello/databases/BikeMaintenance.db: open 
failed: ENOENT (No such file or directory) 
    at libcore.io.IoBridge.open(IoBridge.java:416) 
    at java.io.FileInputStream.(FileInputStream.java:78) 
    at java.io.FileInputStream.(FileInputStream.java:105) 
    at com.example.hello.MainPage.exportdata(MainPage.java:625) 
    at com.example.hello.MainPage.backup(MainPage.java:692) 
    at com.example.hello.MainPage$1.onClick(MainPage.java:494) 
    at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166) 
    at android.os.Handler.dispatchMessage(Handler.java:99) 
    at android.os.Looper.loop(Looper.java:137) 
    at android.app.ActivityThread.main(ActivityThread.java:4745) 
    at java.lang.reflect.Method.invokeNative(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:511) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
    at dalvik.system.NativeStart.main(Native Method) 
Caused by: libcore.io.ErrnoException: open failed: 
ENOENT (No such file or directory) 
    at libcore.io.Posix.open(Native Method) 
    at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110) 
    at libcore.io.IoBridge.open(IoBridge.java:400) 
    ... 14 more 

Answer 1

ваш код выглядит хорошо для меня, но я думаю, что это вы не имеете разрешения на доступ к этому файлу .db вы можете использовать DataBaseHelper класс для доступа к файл .db

public class DataBaseHelper extends SQLiteOpenHelper { 

    private static String DB_PATH = "/data/data/com.android.electricbillgenerator/databases/"; 

     private static String DB_NAME = "BikeMaintenance.db"; 

     private SQLiteDatabase myDataBase; 

     private Context myContext; 

     public static final String COLUMN_ID = "_id"; 
     public static final String COLUMN_USERNAME = "UserName"; 
     public static final String COLUMN_PASSWORD = "Password"; 
     public static final String TABLE_NAME = "Login"; 
     private static final String DATABASE_NAME = "BikeMaintenance.db"; 
     private static final int DATABASE_VERSION = 1; 

    // Database creation sql statement 
//  private static final String DATABASE_CREATE = "create table " 
//   + TABLE_NAME + "(" + COLUMN_ID 
//   + "," + COLUMN_USERNAME 
//   + "," + COLUMN_PASSWORD+ ");"; 

//  private static final String DATABASE_CREATE = "create table " 
//    + TABLE_NAME + "(" + COLUMN_ID 
//    + " integer primary key autoincrement, " + COLUMN_USERNAME 
//    + " text not null," + COLUMN_PASSWORD+ "text not null);"; 

    public DataBaseHelper(Context context) { 
     super(context, DATABASE_NAME, null, 8); 
     this.myContext = context; 

     boolean dbexist = checkDataBase(); 
      if (dbexist) { 
       //System.out.println("Database exists"); 
       openDataBase(); 
      } else { 
       System.out.println("Database doesn't exist"); 
       try { 
        createDataBase(); 
       } catch (IOException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 
      } 

    } 


    @Override 
    public void onCreate(SQLiteDatabase database) { 



//  try { 
//   database.execSQL(DATABASE_CREATE); 
//  } catch (SQLException e) { 
//   // TODO Auto-generated catch block 
//   e.printStackTrace(); 
//  } 

    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
//  Log.w(DataBaseHelper.class.getName(), 
//    "Upgrading database from version " + oldVersion + " to " 
//     + newVersion + ", which will destroy all old data"); 
//   db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME); 
//   onCreate(db); 

    } 




    /** 
    * Creates a empty database on the system and rewrites it with your own database. 
    * */ 
    public void createDataBase() throws IOException{ 

     boolean dbExist = checkDataBase(); 

     if(dbExist){ 
      //do nothing - database already exist 
     }else{ 

      //By calling this method and empty database will be created into the default system path 
       //of your application so we are gonna be able to overwrite that database with our database. 
      this.getReadableDatabase(); 

      try { 

       copyDataBase(); 

      } catch (IOException e) { 

       throw new Error("Error copying database"); 

      } 
     } 

    } 


    /** 
    * Check if the database already exist to avoid re-copying the file each time you open the application. 
    * @return true if it exists, false if it doesn't 
    */ 
    private boolean checkDataBase(){ 

     SQLiteDatabase checkDB = null; 

     try{ 
      String myPath = DB_PATH + DB_NAME; 
      checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY); 

     }catch(SQLiteException e){ 

      //database does't exist yet. 

     } 

     if(checkDB != null){ 

      checkDB.close(); 

     } 

     return checkDB != null ? true : false; 
    } 

    /** 
    * Copies your database from your local assets-folder to the just created empty database in the 
    * system folder, from where it can be accessed and handled. 
    * This is done by transfering bytestream. 
    * */ 
    private void copyDataBase() throws IOException{ 

     //Open your local db as the input stream 
     InputStream myInput = myContext.getAssets().open(DB_NAME); 

     // Path to the just created empty db 
     String outFileName = DB_PATH + DB_NAME; 

     //Open the empty db as the output stream 
     OutputStream myOutput = new FileOutputStream(outFileName); 

     //transfer bytes from the inputfile to the outputfile 
     byte[] buffer = new byte[1024]; 
     int length; 
     while ((length = myInput.read(buffer))>0){ 
      myOutput.write(buffer, 0, length); 
     } 

     //Close the streams 
     myOutput.flush(); 
     myOutput.close(); 
     myInput.close(); 

    } 
    public void openDataBase() throws SQLException{ 

     //Open the database 
     String myPath = DB_PATH + DB_NAME; 
     myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY); 

    } 

    @Override 
    public synchronized void close() { 

      if(myDataBase != null) 
       myDataBase.close(); 

      super.close(); 

    } 



} 

Answer 2

Из Android документации

public FileInputStream (File file) 

Constructs a new FileInputStream that reads from file. 

Parameters 
file the file from which this stream reads. 
Throws 
FileNotFoundException if file does not exist. 

Вы говорите папку, которая существует, но ошибка о файле. Двойная проверка, действительно ли файл существует, возможно, с adb

$ adb shell ls /data/data/com.example.hello/databases/BikeMaintenance.db 

или с разрешения каталога.