为什么我不能读取的只读文件？ [英] Why I can't read a read only file?

问题描述

我有这样的方法应该读取文件：

  / *读取文件的内容* /
    私人的ArrayList＆LT;字符串＆GT; readFromFile（）{
        档案文件=新的文件（jokesBody1.bjk）;
        ArrayList的＆LT;字符串＆GT;名单=新的ArrayList＆LT;字符串＆GT;（）;
        尝试 {
            file.createNewFile（）;
            ObjectInputStream的OIS =新的ObjectInputStream（新的FileInputStream（文件））;
            尝试 {
                名单=（ArrayList中）ois.readObject（）;
            }赶上（ClassNotFoundException异常E）{
                e.printStackTrace（）;
            }
            ois.close（）;
            }赶上（IOException异常E）{
            Log.e（日志活动，无法读取文件：+ e.toString（））;
        }

        返回列表;
    }
 

当我叫它，它返回：

  6月二号至16号：15：32.686：E /日志活动（1380）：无法读取文件：java.io.IOException异常：打开失败：EROFS（只读文件系统）
 

甚至，如果该文件是只读的，我为什么不能看呢？我真的不明白什么是wroong。我有这个premission在我的清单：

＆LT;使用-权限的Andr​​oid：名称=android.permission.READ_EXTERNAL_STORAG​​E/＆GT;

有人可以给我一个线索？我知道我失去了一些东西小，但我真的无法发现它。

下面是我写的文件：

  / *内容写入到文件* /
    私人无效将writeToFile（ArrayList中＆LT;字符串＆GT;清单，上下文续）{
        档案文件=新的文件（jokesBody1.bjk）;
        FileOutputStream中FOS;
        如果（名单！= NULL）{
        尝试 {
                FOS = cont.openFileOutput（jokesBody1.bjk，Context.MODE_PRIVATE）;
                ObjectOutputStream的OUT =新的ObjectOutputStream（FOS）;
                out.writeObject（名单）;
                out.close（）;
        }赶上（FileNotFoundException异常E）{
                e.printStackTrace（）;
        }赶上（IOException异常E）{
                e.printStackTrace（）;
        }
        }其他{
            尝试 {
                file.createNewFile（）;
                FOS = openFileOutput（jokesBody1.bjk，Context.MODE_PRIVATE）;
                ObjectOutputStream的OUT =新的ObjectOutputStream（FOS）;
                out.writeObject（）;
                out.close（）;
        }赶上（FileNotFoundException异常E）{
                e.printStackTrace（）;
        }赶上（IOException异常E）{
                e.printStackTrace（）;
        }
        }
    }
 

解决方案

您要创建文件，这当然无法在只读文件。

删除此行：

  file.createNewFile（）;
 

这是通常用来写入之前创建一个新的空文件。你真的不需要它，如果你只是想读取已存在的文件。

编辑：

只需使用这样的：

  ObjectInputStream的OIS =新的ObjectInputStream（context.openFileInput（jokesBody1.bjk））;
 

当然，你也必须通过上下文的功能。

您只能使用文件用完整路径。为了访问您的私人文件，使用右键，就如同您在保存文件的时候做的。

您全功能应该是这样的：

 私人的ArrayList＆LT;字符串＆GT; readFromFile（上下文的背景下）{
    ArrayList的＆LT;字符串＆GT;名单=新的ArrayList＆LT;字符串＆GT;（）;
    尝试 {
        ObjectInputStream的OIS =新的ObjectInputStream（context.openFileInput（jokesBody1.bjk））;
        尝试 {
            名单=（ArrayList中）ois.readObject（）;
        }赶上（ClassNotFoundException异常E）{
            e.printStackTrace（）;
        }
        ois.close（）;
        }赶上（IOException异常E）{
        Log.e（日志活动，无法读取文件：+ e.toString（））;
    }

    返回列表;
}
 

I have this method supposed to read a file:

 /* Read file's content */
    private ArrayList<String> readFromFile() {
        File file = new File("jokesBody1.bjk");
        ArrayList<String> list = new ArrayList<String>();
        try {
            file.createNewFile();
            ObjectInputStream ois = new ObjectInputStream( new FileInputStream( file ) );
            try {
                list = (ArrayList)ois.readObject();
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
            ois.close();
            } catch (IOException e) {
            Log.e("log activity", "Can not read file: " + e.toString());
        }

        return list;
    }

When I call it, it returns:

02-16 06:15:32.686: E/log activity(1380): Can not read file: java.io.IOException: open failed: EROFS (Read-only file system)

Even, if the file is read only, why I can't read it? I really can't understand what is wroong. I have this premission in my manifest:

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

Can someone give me a clue? I know that I'm missing something small, but I really can't spot it.

Here is how I write the file:

/* Write content to a file */
    private void writeToFile(ArrayList<String> list, Context cont) {
        File file = new File("jokesBody1.bjk");     
        FileOutputStream fos;
        if(list != null){
        try {           
                fos = cont.openFileOutput("jokesBody1.bjk", Context.MODE_PRIVATE);
                ObjectOutputStream out = new ObjectOutputStream(fos);
                out.writeObject(list);
                out.close();
        } catch (FileNotFoundException e) {
                e.printStackTrace();
        } catch (IOException e) {
                e.printStackTrace(); 
        }
        }else{
            try {
                file.createNewFile();
                fos = openFileOutput("jokesBody1.bjk",Context.MODE_PRIVATE);
                ObjectOutputStream out = new ObjectOutputStream(fos);
                out.writeObject("");
                out.close();
        } catch (FileNotFoundException e) {
                e.printStackTrace();
        } catch (IOException e) {
                e.printStackTrace(); 
        }
        }
    }

解决方案

You are trying to create the file, which of course fails on a read-only file.

Remove this line:

file.createNewFile();

This is usually used to create a new empty file before writing to it. You really don't need it if you just want to read a file that already exists.

EDIT:

Just use this:

ObjectInputStream ois = new ObjectInputStream( context.openFileInput("jokesBody1.bjk"));

Of course, you'll also have to pass a Context to the function.

You can only use File with a full path. For accessing your private files, use Context, just as you do when saving the file.

Your full function should look like:

private ArrayList<String> readFromFile(Context context) {
    ArrayList<String> list = new ArrayList<String>();
    try {
        ObjectInputStream ois = new ObjectInputStream( context.openFileInput("jokesBody1.bjk"));
        try {
            list = (ArrayList)ois.readObject();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        ois.close();
        } catch (IOException e) {
        Log.e("log activity", "Can not read file: " + e.toString());
    }

    return list;
}

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