文件的奇怪输出

Question

我在读取文件时遇到输入问题。

文件是在另一个activity制作的，很简单：

ArrayList stuff = new ArrayList();
stuff.add("1,2,3");

try{
String saveFile = "saveGamesTest1.csv";
FileOutputStream saveGames = openFileOutput(saveFile, getApplicationContext().MODE_APPEND);    

ObjectOutputStream save = new ObjectOutputStream(saveGames);

save.writeObject(stuff);    
save.close(); }

另一个activity正在通过

阅读

try {
            FileInputStream fileIn=openFileInput("saveGamesTest1.csv");
            InputStreamReader InputRead = new InputStreamReader(fileIn);

            Scanner s = new Scanner(InputRead).useDelimiter(",");
            System.out.println(s.next());
            System.out.println(s.next());
            System.out.println(s.next());

        }

我期待（并希望）得到像

这样的结果

1
2
3

然而，我得到的结果是这样的：

/storage/emulated/0/Android/data/ys.test/files/saveGamesTest1.csv��sr��java.util.ArrayListx��a��I��sizexp��w��t��1
2
3x

我做错了什么？
.

编辑
我按照下面的建议尝试了 Serializable，如下所示：

public class Save implements java.io.Serializable {
        public String name;
        public String address;
        public transient int SSN;
        public int number;

    }


    public void save(){

        Save e = new Save();
        e.name = "Reyan Ali";
        e.address = "Phokka Kuan, Ambehta Peer";
        e.SSN = 11122333;
        e.number = 101;

        try {
            String saveFile = "save.ser";
            FileOutputStream saveGames = openFileOutput(saveFile, getApplicationContext().MODE_APPEND);
            ObjectOutputStream out = new ObjectOutputStream(saveGames);
            out.writeObject(e);
            out.close();
            saveGames.close();
            System.out.printf("Serialized data is saved in save.csv");
        }
        catch(IOException i) {
            i.printStackTrace();
            out.println("Save exception gepakt");
        }
    }

但是，out.writeObject(e); 给出了一个错误，指出这不是可序列化的

Answer 1

您不是将对象存储为 csv，而是作为序列化 java 对象，您必须将其作为对象而不是 csv 文件来读取

看这里https://www.tutorialspoint.com/java/java_serialization.htm 在序列化一个对象部分

你必须使用

FileInputStream in = null;
ObjectInputStream ois = null;
ArrayList stuff2 = null;
try {
    in = openFileInput("saveGamesTest1.csv");
    ois = new ObjectInputStream(in);
    stuff2 = (ArrayList) ois.readObject();
} catch(IOException e) {...}
catch(ClassNotFoundException c) {...}
finally {
    if (ois != null) {
        ois.close();
    }
    if (in != null) {
        in.close();
    }
}

如果你想要一个 csv 文件，你必须构建它，例如迭代你的数组并在你的文件中一个一个地写入值并添加分隔符或遵循这个 How to serialize object to CSV file?

编辑： Java 7 中序列化对象（此处为列表，如您的示例）和反序列化的一种优雅方式：

public class Main {

public static void main(String[] args) {
    List<Integer> lists = new ArrayList<>();
    List<Integer> readList = null;
    String filename = "save.dat";
    lists.add(1);
    lists.add(2);
    lists.add(3);

    //serialize
    try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(filename))) {
        oos.writeObject(lists);
    } catch (IOException e) {
        e.printStackTrace();
    }
    //don't need to close because ObjectOutputStream implement AutoCloseable interface

    //deserialize
    try (ObjectInputStream oos = new ObjectInputStream(new FileInputStream(filename))) {
        readList = (List<Integer>) oos.readObject();
    } catch (IOException | ClassNotFoundException e) {
        e.printStackTrace();
    }
    //don't need to close because ObjectInputStream implement AutoCloseable interface


    //test
    if(!lists.equals(readList)) {
        System.err.println("error list saved is not the same as the one read");
    }
}

}

文件的奇怪输出

Odd output from file

java

android

fileinputstream

serializable