如何将 SharedPreferences 备份到 SD 卡? [英] How can I backup SharedPreferences to SD card?

问题描述

我在很多地方看到将 SharedPreferences 文件复制到 SD 卡是一个问题，因为每个制造商都将它放在其他地方.

I saw in a lot of places that it's a problem to copy the SharedPreferences file to the sd card because every manufacturer place it somewhere else.

无论文件位于何处，我都想备份到 SD 卡上.有没有办法做到这一点?

I want to backup on the sd card no matter where is the file located. Is there any way to do this?

推荐答案

SharedPreferences 接口包含一个名为 getAll() 的方法，该方法返回一个带有键值的映射对.因此，我没有复制文件本身，而是序列化从此方法返回的映射，然后再将其取回.

The SharedPreferences interface contains a method called getAll() which returns a map with the key-value pairs. So instead of copying the file itself, I just serialize the map that being returned from this method and then retrieve it back afterwards.

一些代码:

private boolean saveSharedPreferencesToFile(File dst) {
    boolean res = false;
    ObjectOutputStream output = null;
    try {
        output = new ObjectOutputStream(new FileOutputStream(dst));
        SharedPreferences pref = 
                            getSharedPreferences(prefName, MODE_PRIVATE);
        output.writeObject(pref.getAll());

        res = true;
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }finally {
        try {
            if (output != null) {
                output.flush();
                output.close();
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
    return res;
}

@SuppressWarnings({ "unchecked" })
private boolean loadSharedPreferencesFromFile(File src) {
    boolean res = false;
    ObjectInputStream input = null;
    try {
        input = new ObjectInputStream(new FileInputStream(src));
            Editor prefEdit = getSharedPreferences(prefName, MODE_PRIVATE).edit();
            prefEdit.clear();
            Map<String, ?> entries = (Map<String, ?>) input.readObject();
            for (Entry<String, ?> entry : entries.entrySet()) {
                Object v = entry.getValue();
                String key = entry.getKey();

                if (v instanceof Boolean)
                    prefEdit.putBoolean(key, ((Boolean) v).booleanValue());
                else if (v instanceof Float)
                    prefEdit.putFloat(key, ((Float) v).floatValue());
                else if (v instanceof Integer)
                    prefEdit.putInt(key, ((Integer) v).intValue());
                else if (v instanceof Long)
                    prefEdit.putLong(key, ((Long) v).longValue());
                else if (v instanceof String)
                    prefEdit.putString(key, ((String) v));
            }
            prefEdit.commit();
        res = true;         
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }finally {
        try {
            if (input != null) {
                input.close();
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
    return res;
}

我希望我帮助了某人，如果这里有什么问题，请告诉我.

I hope that I helped someone, and if something here is wrong please tell me.

埃拉德

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