从sharedpreference（JSON数组）加载数据

Question

I have 4 arrays that I need to be able to save and load to sharedpreference:

String[] debtName = new String[10];
String[] debtAmount = new String[10];
String[] debtRate = new String[10];
String[] debtPayment = new String[10];

Below is my full activity:

import java.util.Arrays;

import org.json.JSONArray;
import org.json.JSONException;

import android.annotation.TargetApi;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Build;
import android.os.Bundle;
import android.view.Menu;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TableRow.LayoutParams;
import android.widget.TextView;

public class DebtList<T> extends Activity {

    String[] debtName = new String[10];
    String[] debtAmount = new String[10];
    String[] debtRate = new String[10];
    String[] debtPayment = new String[10];

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.debtlist);

        JSONArray nameJSONArray = new JSONArray(Arrays.asList(debtName));
        JSONArray amountJSONArray = new JSONArray(Arrays.asList(debtAmount));
        JSONArray rateJSONArray = new JSONArray(Arrays.asList(debtRate));
        JSONArray paymentJSONArray = new JSONArray(Arrays.asList(debtPayment));

        Bundle extras = getIntent().getExtras();

        int trigger = 0;

        //Load Data
        SharedPreferences sharedPrefs= getSharedPreferences("chaosdata", 0);
        //public static JSONArray loadJSONArray(Context c, String prefName, String key)
        ////JSONSharedPreferences.saveJSONArray(this.getApplicationContext(), "prefName", "prefKey", nameJSONArray);

        String jsonString = sharedPrefs.getString("debtNames", "1234");
        if (jsonString != null) {
            JSONArray jsonArray;
            try {
                jsonArray = new JSONArray(jsonString);
                for (int i = 0; i < jsonArray.length(); i++) {
                    debtName[i] = jsonArray.optString(i);
                }
            } catch (JSONException e) {
            }
        }




        //End Load

        for (int i=0;i<10;i++)
        {
            if (debtName[i] == null && extras != null && trigger==0)
            {
                debtName[i] = extras.getString("debtName");
                debtAmount[i] = extras.getString("debtAmount");
                debtRate[i] = extras.getString("debtRate");
                debtPayment[i] = extras.getString("debtPayment");
                trigger = 1;
            }
        }

        TableLayout tl = (TableLayout) findViewById(R.id.debtListTableView);
        for (int i=0;i<10;i++)
        {
            if (debtName[i] != null)
            {

                TableRow tr = new TableRow(this);
                TextView tv0 = new TextView(this);
                TextView tv1 = new TextView(this);
                TextView tv2 = new TextView(this);
                TextView tv3 = new TextView(this);
                TableRow.LayoutParams trlp = new TableRow.LayoutParams();
                tv0.setLayoutParams(new LayoutParams(0, LayoutParams.MATCH_PARENT, 0.25f));
                tv1.setLayoutParams(new LayoutParams(0, LayoutParams.MATCH_PARENT, 0.25f));
                tv2.setLayoutParams(new LayoutParams(0, LayoutParams.MATCH_PARENT, 0.25f));
                tv3.setLayoutParams(new LayoutParams(0, LayoutParams.MATCH_PARENT, 0.25f));
                trlp.span = 3;
                tr.setLayoutParams(trlp);
                tv0.setText("" + debtName[i]);
                tv1.setText("" + debtAmount[i]);
                tv2.setText("" + debtPayment[i]);
                tv3.setText("Holder");
                tr.addView(tv0);
                tr.addView(tv1);
                tr.addView(tv2);
                tr.addView(tv3);
                tl.addView(tr);
            }
        }

        //Save Data
        JSONSharedPreferences.saveJSONArray(this.getApplicationContext(), "chaosdata", "debtNames", nameJSONArray);
        JSONSharedPreferences.saveJSONArray(this.getApplicationContext(), "chaosdata", "debtAmounts", amountJSONArray);
        JSONSharedPreferences.saveJSONArray(this.getApplicationContext(), "chaosdata", "debtRates", rateJSONArray);
        JSONSharedPreferences.saveJSONArray(this.getApplicationContext(), "chaosdata", "debtPayments", paymentJSONArray);
        //End Save


    }

    public static class JSONSharedPreferences {
        private static final String PREFIX = "json";

        public static void saveJSONArray(Context c, String prefName, String key, JSONArray array) {
            SharedPreferences settings = c.getSharedPreferences(prefName, 0);
            SharedPreferences.Editor editor = settings.edit();
            editor.putString(JSONSharedPreferences.PREFIX+key, array.toString());
            editor.commit();
        }

        public static JSONArray loadJSONArray(Context c, String prefName, String key) throws JSONException {
            SharedPreferences settings = c.getSharedPreferences(prefName, 0);
            return new JSONArray(settings.getString(JSONSharedPreferences.PREFIX+key, "[]"));
        }

        public static void remove(Context c, String prefName, String key) {
            SharedPreferences settings = c.getSharedPreferences(prefName, 0);
            if (settings.contains(JSONSharedPreferences.PREFIX+key)) {
                SharedPreferences.Editor editor = settings.edit();
                editor.remove(JSONSharedPreferences.PREFIX+key);
                editor.commit();
            }
        }

    }



    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.debt_list, menu);
        return true;
    }

}

When run, it does not throw any errors. What I'm having problems figuring out is how to retrieve the data back to JSON arrays and then back to arrays so I can manipulate the data in other parts of the application.

Answer 1

public static String getPref(String key, Context context) {
    SharedPreferences preferences= c.getSharedPreferences(prefName, 0);
    return preferences.getString(key, null);
}

Use the above method to get data by passing the key into the method

Answer 2

To retrieve the data back into arrays, you have to iterate over the JSONArray:

String jsonString = prefs.getString("key", null);
if (jsonString != null) {
    JSONArray jsonArray;
    try {
        jsonArray = new JSONArray(jsonString);
        for (int i = 0; i < jsonArray.length(); i++) {
            debtName[i] = jsonArray.optString(i);
        }
    } catch (JSONException e) {
    }
}

For clarification, here's the code I used for testing:

In MainAcitivity:

String[] debtName = {"Douglas", "Fabiano", "Drumond"};
SharedPreferences prefs = getSharedPreferences("com.douglasdrumond.test.prefs", Context.MODE_PRIVATE);
Editor editor = prefs.edit();
JSONArray nameJSONArray = new JSONArray(Arrays.asList(debtName));
editor.putString("com.douglasdrumond.test.debtName", nameJSONArray.toString());
editor.commit();

In SecondActivity:

String[] debtName = new String[3];
SharedPreferences prefs = getSharedPreferences("com.douglasdrumond.test.prefs", Context.MODE_PRIVATE);
String jsonString = prefs.getString("com.douglasdrumond.test.debtName", null);
if (jsonString != null) {
    JSONArray jsonArray;
    try {
        jsonArray = new JSONArray(jsonString);
        for (int i = 0; i < jsonArray.length(); i++) {
            debtName[i] = jsonArray.optString(i);
        }
    } catch (JSONException e) {
    }
}