使用SharedPreferences在Android应用程序中保存String [] []数组

Question

I have read the related posts in this topic and I can not solve my problem. Please take a look at my code and let me know where the problem is.

I want to create a String[10][2] array in my application, so whenever my application starts, it retrieves this array and works around it. The array consists of username and a password corresponding to that username. I want to create new password for new user and retrieve password for already registered user.

public class PasswordGeneration extends Activity {

    private static final String charSet = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!@#$%^&*()_+=-/?";
    private static Random rnd = new Random();
    private String[][] globDataBase = new String[10][2];
    private String password;
    private String temp;
    ImageButton buttonBack;
    TextView setPass;
    String name,genePass;





    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);

        setContentView(R.layout.pass_result);
        buttonBack=(ImageButton)findViewById(R.id.widget54);
        setPass = (TextView)findViewById(R.id.widget51);

        Bundle bundle = getIntent().getExtras();
        name=bundle.getString("name");
        name = "Amir";//for testing, this line should be omitted for real application
        globDataBase = loadDataBase(this);
        genePass = passwordGeneration(name, 12);
        setPass.setText(genePass);


        buttonBack.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {

                finish();

            }
        });


    }



    public String passwordGeneration(String name, int len) {

        for(int i = 0; i < 10; i++){
            if(globDataBase[i][0] == name){
                return globDataBase[i][1];

            }

        }
                StringBuilder sb = new StringBuilder(len);
                for(int j = 0; j < len; j++ )
                sb.append(charSet.charAt(rnd.nextInt(charSet.length())));
                password =  sb.toString();
                setDataBase(name, password);
                return password;
    }

    public void setDataBase(String name, String password){

        for (int i = 0; i < 10; i++){
            if(globDataBase[i][0] == null){
                globDataBase[i][0] = name;
                globDataBase[i][1] = password;
                break;
            }
        }
        saveDataBase(globDataBase, this);
        return;

    }

    public boolean saveDataBase(String[][] db, Context mContext){
        SharedPreferences prefs = mContext.getSharedPreferences("dataBase", 0);
        Editor editor = prefs.edit();
        for(int i = 0; i < 10; i++){
            for(int j = 0; j < 2; j++){
                editor.putString("dataBase", db[i][j]);
            }
        }
        return editor.commit();
    }

    public String[][] loadDataBase(Context mContext){
        SharedPreferences prefs = mContext.getSharedPreferences("dataBase", 0);
        String[][] dataBase = new String[10][2];
        for(int i = 0; i < 10; i++){
            for(int j = 0; j < 2; j++){
            dataBase[i][j] = prefs.getString("dataBase", null);
            }
        }
        return dataBase;
    }
}

When I run my application, I get password for username = "Amir", and when I run the application again, I expect to get the same password, but I get a new one for the same name "Amir". I can not figure out where the problem is.

Answer 1

for(int i = 0; i < 10; i++){
            for(int j = 0; j < 2; j++){
                editor.putString("dataBase", db[i][j]);
            }
        }

this is wrong because you are basically looping and overriding the value for the key "dataBase".

I would suggest you to find another way to save the data. If you still want to use shared preferences you maybe will end up to create several keys for each element like this:

for(int i = 0; i < 10; i++){
            for(int j = 0; j < 2; j++){
                editor.putString("dataBase["+i+"]["+j+"]", db[i][j]);
            }
        }

so you will create entries like "dataBase[0][1]" and then you need the logic to retrieve them... but again, to me looks like a not optimal solution

Answer 2

It seems you may not know how to use key-value container.See the code blew:

//it errors
editor.putString("dataBase", db[i][j]);

After you save your name and password

editor.putString("dataBase", "Amir");
editor.putString("dataBase", "Amirpwd");

you will get "Amirpwd"

prefs.getString("dataBase", null)//it returns "Amirpwd"

Solution:

editor.putString("Amir", "Amirpwd");

you will get the correct pwd

String pwd = prefs.getString("Amir", null)//it returns "Amirpwd"

Answer 3

Another good method is to serialize your array to string (for example to JSON string) and put it to preferences with method putString.

When you will need to get it you can deserialize serialized string.

You can use JSONArray class for serialization.