在Android應用程序中找不到文件

我正在研究一個用作卷書的android應用程序，並且創建了StudentStore類，該類可以執行所有加載並將自定義列表保存到該文件。我的問題是該文件不是在SD卡中創建的;我嘗試了一些東西，但似乎沒有任何工作。在Android應用程序中找不到文件

public class StudentStore { 
public StudentStore(){ 
    Log.d("TAG", "student store constructor"); 
} 
     public SortedDoublyList<Student> loadStudents() throws FileNotFoundException { 
     // sdCard trajectory 
     File sdCard = Environment.getExternalStorageDirectory(); 
     File directory = new File (sdCard.getAbsolutePath() + "/dir1/dir2"); 
     // Creates directory from path held by the variable named directory 
     directory.mkdirs(); 

     File rollBookFile = new File(directory.getAbsolutePath()+"StudentsInfo.txt"); 
     SortedDoublyList<Student> studentList = null; 
     FileInputStream fileInfoIn = null; 
     ObjectInputStream studentInfoIn = null; 

     try { 

      fileInfoIn = new FileInputStream(rollBookFile); 
      studentInfoIn = new ObjectInputStream(fileInfoIn); 
      studentList = (SortedDoublyList<Student>) studentInfoIn.readObject(); 

      studentInfoIn.close(); 
     } 
     catch (IOException ex) { 
      FileOutputStream fileInfoOut = new FileOutputStream(rollBookFile); 
     } catch (ClassNotFoundException ex) { 

     } 

     // Empty file 
     if(studentList == null){ 
      studentList = new SortedDoublyList<Student>(); 
      saveStudents(studentList); 
     } 
     return studentList; 
    } 

     public void saveStudents(SortedDoublyList<Student> studentList) { 
     // sdCard trajectory 
     File sdCard = Environment.getExternalStorageDirectory(); 
     File directory = new File (sdCard.getAbsolutePath() + "/dir1/dir2"); 

     // Creates directory from path held by the variable named directory 
     directory.mkdirs(); 

     // Constructs file from newly obtained directory pointing towards StudentsInfo.txt 
     File rollBookFile = new File(directory.getAbsolutePath()+"StudentsInfo.txt"); 

     FileOutputStream fileInfoOut = null; 
     ObjectOutputStream studentInfoOut = null; 
     try { 
      fileInfoOut = new FileOutputStream(rollBookFile); 
      studentInfoOut = new ObjectOutputStream(fileInfoOut); 
      studentInfoOut.writeObject(studentList); 
      studentInfoOut.close(); 
      System.out.println("Object Persisted"); 
     } 
     catch (IOException ex) { 
      ex.printStackTrace(); 
     } 
    }

來源

2014-04-12 van_helenica

你加入<使用許可權的android：NAME = 「android.permission.WRITE_EXTERNAL_STORAGE」 – nandeesh

謝謝！那正是我錯過的！沒有意識到我會犯這樣一個簡單的錯誤！ –

嘗試添加createNewFile()方法你寫數據之前創建的文件：

try { 
    rollBookFile.createNewFile(); 

    fileInfoOut = new FileOutputStream(rollBookFile); 
    studentInfoOut = new ObjectOutputStream(fileInfoOut); 
    studentInfoOut.writeObject(studentList); 
    studentInfoOut.close(); 
    System.out.println("Object Persisted"); 
}

來源

2014-04-12 07:41:42

謝謝！我錯過了那行代碼和android權限 –

在Android應用程序中找不到文件

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