问题
I am creating an application,In my app I am getting response and displaing it in custom alert dialog, Till here it works fine, Now what I am trying to do is if user selects an item from alert dialog once, it should store it in preference so that no need of fetch the data every time.
Following is my code snippet.
The following response which i am getting is :
{
"states": [
{
"id": "1",
"state_slug": "agra",
"statename": "Agra"
},
{
"id": "2",
"state_slug": "andaman_and_nicobar_islands",
"statename": "Andaman and Nicobar Islands"
},
{
"id": "3",
"state_slug": "andhra_pradesh",
"statename": "Andhra Pradesh"
},
{
"id": "4",
"state_slug": "arunachal_pradesh",
"statename": "Arunachal Pradesh"
},
{
"id": "5",
"state_slug": "assam",
"statename": "Assam"
},
{
"id": "6",
"state_slug": "bihar",
"statename": "Bihar"
},
{
"id": "7",
"state_slug": "bulandshahr",
"statename": "Bulandshahr"
},
{
"id": "8",
"state_slug": "chhattisgarh",
"statename": "Chhattisgarh"
},
{
"id": "9",
"state_slug": "dadra_and_nagar_haveli",
"statename": "Dadra & Nagar Haveli"
},
{
"id": "10",
"state_slug": "daman_and_diu",
"statename": "Daman & Diu"
},
{
"id": "11",
"state_slug": "delhi",
"statename": "Delhi"
},
{
"id": "12",
"state_slug": "farrukhabad",
"statename": "Farrukhabad"
},
{
"id": "13",
"state_slug": "goa",
"statename": "Goa"
},
{
"id": "14",
"state_slug": "gujarat",
"statename": "Gujarat"
},
{
"id": "15",
"state_slug": "haryana",
"statename": "Haryana"
},
{
"id": "16",
"state_slug": "himachal_pradesh",
"statename": "Himachal Pradesh"
},
{
"id": "17",
"state_slug": "jammu_and_kashmir",
"statename": "Jammu & Kashmir"
},
{
"id": "18",
"state_slug": "jharkhand",
"statename": "Jharkhand"
},
{
"id": "19",
"state_slug": "karnataka",
"statename": "Karnataka"
},
{
"id": "20",
"state_slug": "kerala",
"statename": "Kerala"
},
{
"id": "21",
"state_slug": "lakshadweep",
"statename": "Lakshadweep"
},
{
"id": "22",
"state_slug": "madhya_pradesh",
"statename": "Madhya Pradesh"
},
{
"id": "23",
"state_slug": "maharashtra",
"statename": "Maharashtra"
},
{
"id": "24",
"state_slug": "manipur",
"statename": "Manipur"
},
{
"id": "25",
"state_slug": "meghalaya",
"statename": "Meghalaya"
},
{
"id": "26",
"state_slug": "mizoram",
"statename": "Mizoram"
},
{
"id": "27",
"state_slug": "nagaland",
"statename": "Nagaland"
},
{
"id": "28",
"state_slug": "orissa",
"statename": "Orissa"
},
{
"id": "29",
"state_slug": "pondicherry",
"statename": "Pondicherry"
},
{
"id": "30",
"state_slug": "punjab",
"statename": "Punjab"
},
{
"id": "31",
"state_slug": "purulia",
"statename": "Purulia"
},
{
"id": "32",
"state_slug": "rajasthan",
"statename": "Rajasthan"
},
{
"id": "33",
"state_slug": "sikkim",
"statename": "Sikkim"
},
{
"id": "34",
"state_slug": "tamil_nadu",
"statename": "Tamil Nadu"
},
{
"id": "35",
"state_slug": "tripura",
"statename": "Tripura"
},
{
"id": "36",
"state_slug": "uttar_pradesh",
"statename": "Uttar Pradesh"
},
{
"id": "37",
"state_slug": "uttarakhand",
"statename": "Uttarakhand"
},
{
"id": "38",
"state_slug": "west_bengal",
"statename": "West Bengal"
}
]
}
I am displaying statename in my alert dialog,
class LoadAllStates extends AsyncTask<String, String, ArrayList<HashMap<String,String>>> {
ArrayAdapter<String> adapterallstates ;
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Please wait..");
pDialog.setIndeterminate(true);
// pDialog.setIndeterminateDrawable(getResources().getDrawable(R.drawable.custom_progress));
pDialog.setCancelable(true);
pDialog.show();
}
protected ArrayList<HashMap<String,String>> doInBackground(String... args) {
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
statedata = new ArrayList<HashMap<String, String>>();
String jsonStr = sh.makeServiceCall(STATE_URL, ServiceHandler.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
state_list = jsonObj.getJSONArray(COUNTRY_LIST);
// looping through All Contacts
for (int i = 0; i < state_list.length(); i++) {
JSONObject c = state_list.getJSONObject(i);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(STATE_SLG, c.getString(STATE_SLG));
map.put(STATE_ID, c.getString(STATE_ID));
map.put(STATE_NAME,c.getString(STATE_NAME));
statedata.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return statedata;
}
protected void onPostExecute(ArrayList<HashMap<String,String>> result) {
super.onPostExecute(result);
pDialog.dismiss();
String[] arrallstates=new String[statedata.size()];
for(int index=0;index<statedata.size();index++){
HashMap<String, String> map=statedata.get(index);
arrallstates[index]=map.get(STATE_NAME);
}
// pass arrConuntry array to ArrayAdapter<String> constroctor :
adapterallstates = new ArrayAdapter<String>(MainActivity.this,
android.R.layout.simple_spinner_dropdown_item,
arrallstates);
spstate.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View w) {
new AlertDialog.Builder(MainActivity.this)
.setTitle("Select")
.setAdapter(adapterallstates, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
spstate.setText(adapterallstates.getItem(which).toString());
try {
String n = state_list.getJSONObject(which).getString("state_slug");
statename=state_list.getJSONObject(which).getString("state_slug");
stnm=state_list.getJSONObject(which).getString(STATE_NAME);
Log.d("Response statenm: ", "> " + statename);
SharedPreferences.Editor editor = sharedpreferences.edit();
editor.putString(States, n);
editor.commit();
new LoadAllStatesCity().execute();
// Toast.makeText(getActivity(), statename, Toast.LENGTH_LONG).show();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
dialog.dismiss();
}
}).create().show();
}
});
}
}
回答1:
if you want to store the response the better way is to write the content into a file.if you want to store only some values you can do like this
SharedPreferences.Editor editor = getSharedPreferences(MY_PREFS_NAME, MODE_PRIVATE).edit();
editor.putString("key_from_json", "String_value_from_json");
editor.putInt("key_from_json","int_value_from_json");
editor.commit();
回答2:
SharedPreferences it is prefered for storing small data. Hence to save your entire response it is better you save it to a file (ex: .bin) like so:
public static synchronized void saveToFileSystem(Context context, Object object, String binFileName) {
try {
String tempPath = context.getFilesDir() + "/" + binFileName + ".bin";
File file = new File(tempPath);
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file));
oos.writeObject(object);
oos.flush();
oos.close();
} catch (Exception e) {
e.printStackTrace();
}
}
and for reading it you can do smth like:
public static synchronized Object readFromFileSystem(Context context, String binFileName) {
Object obj = new Object();
try {
String tempPath = context.getFilesDir() + "/" + binFileName + ".bin";
File file = new File(tempPath);
if (file.exists()) {
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file));
obj = ois.readObject();
ois.close();
}
} catch (Exception e) {
e.printStackTrace();
}
return obj;
}
回答3:
You can easily save your JSON file completely as a string variable with a key in shared preferences and pars it when you aim to read it again.
回答4:
You can store your whole object class in preference using gson.jar file -> click here
And to use it...
static public void setPreferenceObject(Context c, Object modal,String key) {
/**** storing object in preferences ****/
SharedPreferences appSharedPrefs = PreferenceManager.getDefaultSharedPreferences(
c.getApplicationContext());
Editor prefsEditor = appSharedPrefs.edit();
Gson gson = new Gson();
String jsonObject = gson.toJson(modal);
prefsEditor.putString(key, jsonObject);
prefsEditor.commit();
}
static public Object getPreferenceObjectJson(Context c,String key) {
SharedPreferences appSharedPrefs = PreferenceManager.getDefaultSharedPreferences(
c.getApplicationContext());
/**** get user data *****/
String json = appSharedPrefs.getString(key, "");
Gson gson=new Gson();
User selectedUser=gson.fromJson(json, User.class);
return selectedUser;
}
回答5:
I'd store the selected value in a key in SharedPreferences. Then, at startup, you'll be able to load SharedPreferences to check whether you already have a value or not (and in that case, you can reload your JSON entirely)
Guide here.
IMMO, it's useless to save a file if you're just looking for storing a value. That's where SharedPreferences are supposed to be used: they are kept even if you close your application and restart it.
回答6:
Data for states does not change for years so you can keep this json data in assets and use it from there or keep it in a static map. instead of calling webservice to fetch it.
for persisting the selected value, you can use SharedPreferences and store state id in it. next time whenever you inflate list of states you can check in your shared preference and select the one which is saved.
回答7:
Basically you could check if the value of preferences is stored or not.
you could do this onCreate() method:
Check if preference value exists
if yes:
then no need to make AsyncTask call
and if no:
then make the AsyncTask call
Code:
String statename = preferences.getString("STATE_NAME<name you gave while committing for first time>,"");
if(statename!=""){
//Then directly go inside main activity
}
else{
//Make AsyncTask Call
}
来源：https://stackoverflow.com/questions/33208205/how-to-store-json-object-to-shared-preferences