How to store a class object into Internal Memory Storage using serializable?

Question

I need to store this object into the internal storage memory of the phone, and i have the <uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE"></uses-permission> set on the manifest. The object itself haves two static methods for store and reload it from the internal memory:

public class SaveState implements Serializable {
static public List<FullMagazine> fms = new ArrayList<FullMagazine>();
static SaveState instance=null;

public static SaveState getInstance(){      
    if( instance == null )
        instance = new SaveState();     
    return instance;
}

public static void saveData(SaveState instance){
    ObjectOutput out;
    try {
        out = new ObjectOutputStream(new FileOutputStream("appSaveState.data"));        
        out.writeObject(instance);
        out.close();
    } catch (Exception e) {e.printStackTrace();}
}

public static SaveState loadData(){
    ObjectInput in;
    SaveState ss=null;
    try {
        in = new ObjectInputStream(new FileInputStream("appSaveState.data"));       
        ss=(SaveState) in.readObject();
        in.close();
    } catch (Exception e) {e.printStackTrace();}
    return ss;
}
}

I'm trying to store it and reopen it using this call in my activity:

            SaveState.fms.add(fm);
            SaveState.saveData(SaveState.getInstance());                
            SaveState sv = SaveState.loadData();

But it is not working, it is not storing the object, and ofcourse it is not reading the objecto, i'm getting these two exception while storing and reading the object:

    03-23 09:18:16.702: WARN/System.err(9060): java.io.FileNotFoundException: /appSaveState.data (Read-only file system)
03-23 09:18:16.702: WARN/System.err(9060):     at org.apache.harmony.luni.platform.OSFileSystem.openImpl(Native Method)
03-23 09:18:16.702: WARN/System.err(9060):     at org.apache.harmony.luni.platform.OSFileSystem.open(OSFileSystem.java:152)
03-23 09:18:16.702: WARN/System.err(9060):     at java.io.FileOutputStream.<init>(FileOutputStream.java:97)
03-23 09:18:16.702: WARN/System.err(9060):     at java.io.FileOutputStream.<init>(FileOutputStream.java:168)
03-23 09:18:16.702: WARN/System.err(9060):     at java.io.FileOutputStream.<init>(FileOutputStream.java:147)
03-23 09:18:16.702: WARN/System.err(9060):     at com.Magazine.SaveState.saveData(SaveState.java:35)
03-23 09:18:16.702: WARN/System.err(9060):     at com.Magazine.MainMenu$DownloadThread.run(MainMenu.java:807)
03-23 09:18:16.709: WARN/System.err(9060): java.io.FileNotFoundException: /appSaveState.data (No such file or directory)
03-23 09:18:16.709: WARN/System.err(9060):     at org.apache.harmony.luni.platform.OSFileSystem.openImpl(Native Method)
03-23 09:18:16.709: WARN/System.err(9060):     at org.apache.harmony.luni.platform.OSFileSystem.open(OSFileSystem.java:152)
03-23 09:18:16.709: WARN/System.err(9060):     at java.io.FileInputStream.<init>(FileInputStream.java:82)
03-23 09:18:16.709: WARN/System.err(9060):     at java.io.FileInputStream.<init>(FileInputStream.java:134)
03-23 09:18:16.709: WARN/System.err(9060):     at com.Magazine.SaveState.loadData(SaveState.java:46)
03-23 09:18:16.709: WARN/System.err(9060):     at com.Magazine.MainMenu$DownloadThread.run(MainMenu.java:809)

What's wrong in the code?

Thanks

The problem is that you are trying to write to / which is read only in android. — Menachem Hornbacher, Jun 09 '16 at 23:29
Does the class used in the static List, `FullMagazine` also implements Serializable ? — Sharp Edge, Sep 02 '16 at 16:27

Blackbelt · Accepted Answer · 2014-09-26T10:53:16.923

6

change this

out = new ObjectOutputStream(new FileOutputStream("appSaveState.data"));

with

   File outFile = new File(Environment.getExternalStorageDirectory(), "appSaveState.data");
   out = new ObjectOutputStream(new FileOutputStream(outFile));

as correctly pointed out by @e-x, the file will not be removed clearing application's data or uninstalling the app

edited Sep 26 '14 at 10:53

answered Mar 23 '12 at 09:27

Blackbelt

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and what happens if the phone doesn't have a SDCARD installed? i'm trying to store it on the internal memory storage because i must store this data on all the phones, including the phones without SDCARD – NullPointerException Mar 23 '12 at 09:29
1

if you are referring to mobile phones without sdcard support (like the samsung nexus s), the Enviromenet.getExternalStorageDirectory() will return the path to the phone internal storage archive. – Blackbelt Mar 23 '12 at 09:36
1

I think it's worth mentioning that if the phone has an SDCARD then the file will remain when clearing the application's data. – E_X Sep 26 '14 at 10:43
@E_X, I updated the answer, thanks for the contribution – Blackbelt Sep 26 '14 at 10:53

score 2 · Answer 2 · answered Mar 23 '12 at 09:25

2

You're not allowed to just write into the internal storage (even if you get that permission). Try it with the external sd or your cache folder instead.

answered Mar 23 '12 at 09:25

Tim

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Cachefolder data is persisent until the app is uninstalled from the phone? tell me how to do it with the cache folder please, what i should change into my code? – NullPointerException Mar 23 '12 at 09:28
File cacheFile = new File(activity.getCacheDir(), "appSaveState.data"); - write into that file like you did before. – Tim Mar 23 '12 at 09:32
2

Cachefolder is prone to be deleted by OS when free space is becoming low! – Dumbo Jul 03 '14 at 01:43

score 1 · Answer 3 · answered Aug 05 '13 at 21:14

This was my aproach based on this post and this

I wrote this on my User class

private static File mFolder;
public void saveData(Activity pContext) {
    //this could be initialized once onstart up
    if(mFolder == null){
        mFolder = pContext.getExternalFilesDir(null);
    }
    this.save();
    ObjectOutput out;
    try {
        File outFile = new File(mFolder,
                "someRandom.data");
        out = new ObjectOutputStream(new FileOutputStream(outFile));
        out.writeObject(this);
        out.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public static User loadData(Context pContext) {
    if(mFolder == null){
        mFolder = pContext.getExternalFilesDir(null);
    }
    ObjectInput in;
    User lUser = null;
    try {
        FileInputStream fileIn = new FileInputStream(mFolder.getPath() + File.separator + "someRandom.data");
        in = new ObjectInputStream(fileIn);
        lUser = (User) in.readObject();
        in.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
    if (lUser != null) {
        lUser.save();
        Log.d("current User: ", lUser.nickname);
    } else {
        Log.d("current User: ", "null");
    }
    return lUser;
}

Edit:

Then from my activity i call

mUser = User.loadData(mSelf);

or

mUser = User.loadData(this);

mSelf would be an instance I store

Hope this helps :)

How to store a class object into Internal Memory Storage using serializable?

3 Answers3

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