阅读从内部存储一个ArrayList [英] Read an ArrayList from Internal Storage

问题描述

我有一个Android应用程序，我想读，写的的ArrayList＆LT; MyClass的＆GT; 的内部存储

I have an Android application and I would like to read and write an ArrayList<MyClass> to the Internal Storage.

写作部分作品（我相信，没有测试它尚未:-)）：

The writing part works (I believe, haven't tested it yet :-) ) :

ArrayList<MyClass> aList;

    public void saveToInternalStorage() {
    try {
        FileOutputStream fos = ctx.openFileOutput(STORAGE_FILENAME, Context.MODE_PRIVATE);
        fos.write(aList.toString().getBytes());
        fos.close();
    }
    catch (Exception e) {
        Log.e("InternalStorage", e.getMessage());
    }
}

但我想从存储现在​​要做的就是阅读整个ArrayList和回击像这样一个ArrayList

But what I want to do now is read the whole ArrayList from the Storage and return it as an ArrayList like so:

public ArrayList<MyClass> readFromInternalStorage() {
        ArrayList<MyClass> toReturn;
        FileInputStream fis;
        try {
            fis = ctx.openFileInput(STORAGE_FILENAME);

            //read in the ArrayList
            toReturn = whatever is read in...

            fis.close();
        } catch (FileNotFoundException e) {
            Log.e("InternalStorage", e.getMessage());
        } catch (IOException e) {
            Log.e("InternalStorage", e.getMessage()); 
        }
        return toReturn
}

我从来没有读过之前与Android的文件，所以我不知道这甚至有可能。 但是，有没有办法，我可以在我的自定义读的ArrayList ？

I've never read in a file with Android before, so I don't know if this is even possible. But is there A way I can read in my custom ArrayList?

推荐答案

您必须序列化/反序列化对象：

you have to serialize/deserialize your object:

您MyClass的必须implments序列化和里面所有MyClass的成员必须是可序列化

Your MyClass must implments Serializable and all the member inside MyClass must be serializable

 public void saveToInternalStorage() {
        try {
            FileOutputStream fos = ctx.openFileOutput(STORAGE_FILENAME, Context.MODE_PRIVATE);
            ObjectOutputStream of = new ObjectOutputStream(fos);
            of.writeObject(aList);
            of.flush();
            of.close();
            fos.close();
        }
        catch (Exception e) {
            Log.e("InternalStorage", e.getMessage());
        }
}

反序列化对象：

to deserialize the object:

public ArrayList<MyClass> readFromInternalStorage() {
    ArrayList<MyClass> toReturn;
    FileInputStream fis;
    try {
        fis = ctx.openFileInput(STORAGE_FILENAME);
        ObjectInputStream oi = new ObjectInputStream(fis);
        toReturn = oi.readObject();
        oi.close();
    } catch (FileNotFoundException e) {
        Log.e("InternalStorage", e.getMessage());
    } catch (IOException e) {
        Log.e("InternalStorage", e.getMessage()); 
    }
    return toReturn
} 

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