SharedPreferences to a custom path - Android

Question

I want to keep my SharedPreferences xml in a different place where default path is the application package.

Can we set a custom path for android SharedPreferences and use it while it is in that path ?

Answer 1

You can create a adapter to get preferences.

First, create an interface IPreferences (Not necessary but make your life easier if you want to change it back or change to another method):

public interface IPreferences {
    boolean contains(String key);
    int getInt(String key, int defValue);
    String getString(String key, String defValue);
    void putInt(String key, int value);
    void putString(String key, String value);
}

(Some methods are left out, most of them are redundant)

Then, you implement with a xml storage class XMLPreferences.

public class XMLPreferences implements IPreferences {
    private final String path;

    public XMLPreferences(String path) {
        this.path = path;
    }

    @Override
    public boolean contains(String key) {
        return getContentByKey(key) == null;
    }

    @Override
    public int getInt(String key, int defValue) {
        if( getContentByKey(key) == null)
            return defValue;
        return Integer.valueOf(key);
    }

    @Override
    public String getString(String key, String defValue) {
        if( getContentByKey(key) == null)
            return defValue;
        return defValue;
    }

    @Override
    public void putInt(String key, int value) {
        putContentByKey(key, value);
    }

    @Override
    public void putString(String key, String value) {
        putContentByKey(key, value);
    }

    private String getContentByKey(String key) {
        try {
            FileInputStream fileInputStream = new FileInputStream(path);
            DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
            Document dom = builder.parse(fileInputStream);
            Element root = dom.getDocumentElement();
            NodeList nodes = root.getElementsByTagName(key);
            if (nodes.getLength() > 0)
                return nodes.item(0).getTextContent();
        } catch (ParserConfigurationException | SAXException | IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    private void putContentByKey(String key, String content) {
        try {
            FileInputStream fileInputStream = new FileInputStream(path);
            DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
            Document dom = builder.parse(fileInputStream);
        Element root = dom.getDocumentElement();
            NodeList nodes = root.getElementsByTagName(key);
            if (nodes.getLength() > 0)
                nodes.item(0).setTextContent(content);
            else {
                Element newElement = dom.createElement(key);
                newElement.setTextContent(content);
                root.appendChild(newElement);
            }
            Transformer transformer = TransformerFactory.newInstance().newTransformer();
            Result output = new StreamResult(new File(path));
            Source input = new DOMSource(dom);
            transformer.transform(input, output);
        } catch (ParserConfigurationException | SAXException | IOException | TransformerException e) {
            e.printStackTrace();
        }
    }
}

Finally, you can call the following:

IPreferences pref = new XMLPreferences(YOUR_PATH);

Later, if you want to change the implementation, you can implement a new class with IPreferences. Then, you can just change the initialization without changing other parts.

P.S. This uses DOM Praser which may facing performance issue if you have a large XML file. You may want use other XML Praser instead

Answer 2

Big thanks to @Joshua This answer is inspired by his code, i added something to the same interface and i implemented it with Json,

public interface IPreferences {
    boolean contains(String key);

    int getInt(String key, int defValue);
    String getString(String key, String defValue);
    boolean getBoolean(String key, boolean defValue); // added

    void putInt(String key, int value);
    void putBoolean(String key, boolean value); // added
    void putString(String key, String value);

    // easiness of use
    void put(String key, String value);
    void put(String key, int value);
    void put(String key, boolean value);
}

and this is the implementation with Json :

public class MBJsonSharedPrefs implements IPreferences {

    String filePath;
    JSONObject mJSONObject;

    public MBJsonSharedPrefs(String filePath){
        this.filePath = filePath;
        try {
            if(!MBFileUtils.FileExists(filePath)){
                // this is important for the first time
                MBFileUtils.CreateFile(filePath, "{}"); // put empty json object
            }
            String json = MBFileUtils.ReadFile(filePath);
            mJSONObject = new JSONObject(json);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public boolean contains(String key) {
        if(mJSONObject== null) return false;
        return mJSONObject.has(key);
    }

    @Override
    public int getInt(String key, int defValue) {
        return tryParseInt(getContentByKey(key), defValue);
    }

    private int tryParseInt(String strVal, int defValue){
        if(strVal == null) return defValue;
        try{return Integer.parseInt(strVal);}
        catch (Exception e){return defValue;}
    }

    @Override
    public String getString(String key, String defValue) {
        String value = getContentByKey(key);
        return value==null?defValue:value;
    }

    @Override
    public boolean getBoolean(String key, boolean defValue) {
        String value = getContentByKey(key);
        return value==null?defValue:value.equals("t");
    }

    @Override
    public void putInt(String key, int value) {
        putContentByKey(key, value+"");
    }

    @Override
    public void put(String key, int value) {
        putInt(key, value);
    }

    @Override
    public void putString(String key, String value) {
        putContentByKey(key, value);
    }

    @Override
    public void put(String key, String value) {
        putString(key, value);
    }

    @Override
    public void putBoolean(String key, boolean value) {
        putContentByKey(key, value?"t":"f");
    }

    @Override
    public void put(String key, boolean value) {
        putBoolean(key, value);
    }

    public void commit() {
        if(mJSONObject == null) return;
        try {
            MBFileUtils.WriteToFile(mJSONObject.toString(), filePath);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void apply() {
        MBThreadUtils.DoOnBackground(new Runnable() {
            @Override
            public void run() {
                commit();
            }
        });
    }

    private String getContentByKey(String key) {
        if(mJSONObject == null) return null;
        if(!contains(key)) return null;
        try {
            return (String)mJSONObject.get(key);
        } catch (JSONException e) {
            e.printStackTrace();
            return null;
        }
    }

    private void putContentByKey(String key, String content) {
        if(mJSONObject == null) return;
        try {
            mJSONObject.put(key, content);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

and this is how i use it:

// getting string 
MBJsonSharedPrefs pref = new MBJsonSharedPrefs(pathToFile/settings.json).getString(KET_ID,"Default");
pref.apply(); // important to write to file
// putting string
MBJsonSharedPrefs pref = new MBJsonSharedPrefs(pathToFile/settings.json).putString(KET_ID,"111222333");
pref.apply(); 
// OR another way for putting string into the file
MBJsonSharedPrefs pref = new MBJsonSharedPrefs(pathToFile/settings.json).put(KET_ID,"111222333");
pref.apply();

This worked for me, Again thanks to @Joshua for his answer

Answer 3

No, you can't, because in Android every application has his own sandbox. The only thing you can do - set name for SharedPreferences file (for the case, if you want to have different setting files):

SharedPreferences mSettings = context.getSharedPreferences(prefName, Context.MODE_PRIVATE);

Where prefName is name of the settings file.

Answer 4

Simple thing I am doing. On startup (before anything) I copy my private preferences file from my own location to the location of the app app.folders/shared_prefs.

On shutdown of the app I copy the shared preferences back to my private folder...

I do this so that I don't loose some important settings between apk uninstall/install when I need to completely wipe up the old apk installation.