在共享首选项中存储字符串时如何写而不覆盖

Question

Storing Strings :

Encryption encryption = Encryption.getDefault("Key", "Salt", new byte[16]);
                String encryptedP = encryption.encryptOrNull(Password);
                String encryptedU = encryption.encryptOrNull(Username);    
            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(MainActivity.this);
            Editor edit = prefs.edit();
            edit.putString("Password", encryptedP);
            edit.putString("Username", encryptedU);
            edit.commit(); 

Retrieving Strings :

Encryption encryption = Encryption.getDefault("Key", "Salt", new byte[16]);
    String encryptedP = encryption.encryptOrNull(Password);
    String encryptedU = encryption.encryptOrNull(Username);
    SharedPreferences sPrefs = PreferenceManager.getDefaultSharedPreferences(LoginActivity.this);
    String UsernamePref = sPrefs.getString("Username", "");
    String PasswordPref = sPrefs.getString("Password", "");
    if(encryptedU.equals(UsernamePref) &&  (encryptedP.equals(PasswordPref))) {  if((NewPassword.matches (ConfirmPassword))) {
                Editor edit = sPrefs.edit();
                edit.putString("Password", encryptedN);
                edit.commit();          

When retrieving, unless i am retrieving the last strings stored, it will not succeed as it will not look on all lines. Only the first line, how do i change this so that it scans every line before closing file ? Thanks

Edit : Okay so i just realised its overwriting each time, not actually storing it onto a new line, which is why it can't retrieve "old strings", new question. How do i store and not overwrite each time i create a new user ?

Answer 1

This "error" is because you are not storing the preferences properly:

you need to commit the preferences in the editor

do:

SharedPreferences spref = getSharedPreferences("your_prefs_name", Activity.MODE_PRIVATE);
SharedPreferences.Editor editor = spref.edit();
editor.putString("myTextViewValue", prefVal); 
editor.commit(); // HERE add this line!!!

Answer 2

I think it would be better if you used a database. Using shared prefs to store a large amount of data needs a lot of complicated code.

Every time you need to store a lot of entries of the same kind of data, in this case, passwords and usernames, you should use a database instead of shared prefs.

I know that setting up an SQLite database in android is very annoying and requires a lot of code. So to simplify things a bit, I recommend the SugarORM library. It is an object relational mapping (ORM) library that just simplifies your experience in using an SQLite database

Basically, you create a table in the database by creating a class that extends SugarRecord

public class User extends SugarRecord<User> {
    public String username;
    public String password;

    public User () {} // parameterless constructor is required
    public User (String username, String password) {
        this.username = username;
        this.password = password;
    }
}

When you want to save a new user to the database, it is as simple as

User u = new User("Sweeper", "123456");
u.save();

You can use methods such as listAll , find , findById to query the database! One to many relationships are supported!

You can find more information on the website.

Answer 3

To store records in the SharedPreferences for each user you can modify the preferences key. It will prevent overwriting the values.

For instance

String getFormattedName(String username, String value) {
    return String.format("%s_%s", username, value);
}

Then you can store the records like this:

edit.putString(getFormattedName(encryptedU, "Password"), encryptedP);
edit.putString(getFormattedName(encryptedU, "Username"), encryptedU);

and retrieve:

String UsernamePref = sPrefs.getString(getFormattedName(encryptedU, "Username"), "");
String PasswordPref = sPrefs.getString(getFormattedName(encryptedU, "Password"), "");

So the key will be like 123123_Username . Of cource you can modify the pattern as you need.

Answer 4

package com.example.preferences;

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.SharedPreferences;
import android.support.annotation.NonNull;

public class DumbPref {
    private SharedPreferences mPreferences;

    public DumbPref(@NonNull Context context, @NonNull String name) {
        mPreferences = context.getSharedPreferences(name, Context.MODE_PRIVATE);
    }

    @SuppressLint("CommitPrefEdits")
    public void addUser(@NonNull String name, @NonNull String password) {
        SharedPreferences.Editor editor = mPreferences.edit();
        editor.putBoolean(makeKey(name, password), true);
        editor.commit();
    }

    public boolean isAuthenticated(String name, String password) {
        return mPreferences.getBoolean(makeKey(name, password), false);
    }

    private static String makeKey(String name, String password) {
        return name + "_" + password;
    }
}