Develop Reference

Save a List of custom object in savedInstanceState

I am currently building an app to retrieve information for a remote server. the data received are JSON and I am build a list of Data using the class below :
public class RedditData {
private RedditTopic data;
public RedditTopic getData() {
return data;
}
}
and RedditTopic class is defined as below:
public final class RedditTopic {
private static final String TAG = RedditTopic.class.getSimpleName();
private String author;
private String thumbnail;
private String title;
private String num_comments;
private long created_utc;
private String data;
private String name;
public RedditTopic(){};
public String getData() {
return data;
}
public String getAuthor() {
return author;
}
public String getThumbnail(){
return thumbnail;
}
public String getTitle(){
return title;
}
public String getComments(){
return num_comments + " comments";
}
public long getCreated_utc(){
return created_utc;
}
public String getRedditName(){
return name;
}
}
both of these classes are used to translate a JSON into an Object formatted data.
I do not want to really change them to make them Parceable to avoid impacting the extraction of JSON.
I have added :
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
Log.d(TAG, ">>>>>>>>>>>>>>>>>>>>>>>> SAVE");
savedInstanceState.putParcelableArrayList("RedditList", myListOfData );
super.onSaveInstanceState(savedInstanceState);
}
#Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
Log.d(TAG, ">>>>>>>>>>>>>>>>>>>>>>>> RESTORE");
List<RedditData> myListOfData = savedInstanceState.getParcelableArrayList("RedditList");
}
Android complain because I need to implement Parceable in my class RedditData and I assume probably in the RedditTopic Class as well because RedditData returned a List of RedditTopic.
Is there a better way to do it? keep the List as I have it without requiring the Parceable option.
I do not have a List of String, it's a list of object.
Any idea?
Regards

Make your model objects parcleable.
There is a great extension, https://plugins.jetbrains.com/plugin/7332-android-parcelable-code-generator that will generate the neccesary parcelable methods for your class.
I highly recommend it.

Not receiving data from server using Retrofit 2

I am trying to retrieve Reddit information from a particular subreddit using Retrofit 2. I have followed many tutorials and videos and my code seems to be correct from my perspective but I only manage to have null objects in my model class. I have the permission for internet in the Manifest.
This is a link the JSON I am working with HERE
MainActivity
public class MainActivity extends AppCompatActivity
{
TextView mTextView;
Data mData;
private static final String TAG = "Battlestations";
#Override
protected void onCreate(Bundle savedInstanceState)
{
mTextView = (TextView) findViewById(R.id.test_view);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Call<Data> serviceCall = Service.getDesktopService().desks();
serviceCall.enqueue(new Callback<Data>()
{
#Override
public void onResponse(Call<Data> call, Response<Data> response)
{
Log.d("Reponce","return");
Log.i(TAG, "Response is " + mData.getChildren());
}
#Override
public void onFailure(Call<Data> call, Throwable t)
{
}
});
}
}
Api/Service Class
public class Service
{
private static final String BASE_URL = "https://www.reddit.com/r/";
private static DeskInterface mRetrofit;
public static DeskInterface getDesktopService()
{
if(mRetrofit == null)
{
Retrofit build = new Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build();
mRetrofit = build.create(DeskInterface.class);
}
return mRetrofit;
}
public interface DeskInterface
{
#GET("battlestations/hot/.json")
Call<Data> desks();
}
}
Data
public class Data
{
private List<Child> children = null;
public List<Child> getChildren()
{
return children;
}
public void setChildren(List<Child> children)
{
this.children = children;
}
}
Child
public class Child
{
private Data_ data;
public Data_ getData()
{
return data;
}
public void setData(Data_ data)
{
this.data = data;
}
}
Data_
public class Data_
{
private String subreddit;
private Integer score;
private String author;
private String subredditNamePrefixed;
private String url;
private String title;
public String getSubreddit()
{
return subreddit;
}
public void setSubreddit(String subreddit)
{
this.subreddit = subreddit;
}
public Integer getScore()
{
return score;
}
public void setScore(Integer score)
{
this.score = score;
}
public String getAuthor()
{
return author;
}
public void setAuthor(String author)
{
this.author = author;
}
public String getSubredditNamePrefixed()
{
return subredditNamePrefixed;
}
public void setSubredditNamePrefixed(String subredditNamePrefixed)
{
this.subredditNamePrefixed = subredditNamePrefixed;
}
public String getUrl()
{
return url;
}
public void setUrl(String url)
{
this.url = url;
}
public String getTitle()
{
return title;
}
public void setTitle(String title)
{
this.title = title;
}
}

You need to add mData = response.body() in onResponse() (also check response.isSuccessful() first)

The problem is that your Data does not correspond with Reddit JSON. Your Data class
public class Data {
private List<Child> children = null;
}
does not match with the given json, which is:
{
"kind":"listing",
"data":{
"modhash":"...",
"children":[...],
"after":"...",
"before":"..."
}
}
Retrofit automagically convert from json to java but only if the mapping is correct.
A correct Java class would be:
public class Subreddit {
String kind;
Data data;
}
public class Data{
String modhash;
List<Child> children;
String after;
String before;
}
and then modify desks method interface to
Call<Subreddit> desks();
You would have to go recursively for the entire depth of the JSON to get the right mapping.
But before you get to work, just replace your Retrofit interface:
public interface DeskInterface{
#GET("battlestations/hot/.json")
Call<Data> desks();
}
with:
public interface DeskInterface{
#GET("battlestations/hot/.json")
Call<JsonObject> desks();
}
and it should return something. If is still null, then further investigation is needed. If it returns a valid response(some json text) then copy/paste that subreddit to this website where it converts all the json to a valid Java class

how to get object's attributes

How can I get an object's attributes?
I created an object that has two fields, first one called Title containing the string value "title1" and second one called Description containing the string value "description1". I would like to get the strings inside.
The method item.toString() gets me the two strings one after the other. Is there a way to get the strings separatively?

Just create accessor methods for each field.
Assuming you have declared your fields like this:
private String title;
private String desciption;
create the accessor methods in your class definition like this:
public String getTitle() {
return title;
}
public String getDescription() {
return description;
}
then you just call these methods to get the appropriate value.

Class Declaration
public class Class_Name {
private String Category;
private String Category_Type;
public Class_Name () {
super();
}
public Class_Name(String Category, String Category_Type) {
super();
this.Category = Category;
this.Category_Type = Category_Type;
}
/*public Class_Name (String Category_Type) {
this.Category_Type = Category_Type;
}*/
public String getCategory() {
return Category;
}
public void setCategory(String Category) {
this.Category = Category;
}
public String getCategory_Type() {
return Category_Type;
}
public void setCategory_Type(String Category_Type) {
this.Category_Type = Category_Type;
}
}
In the class where you should use this Object to store and retrieve values.
//Create an object for this class
private Class_Name data;
// To save values
data.setCategory(sCategory);
data.setCategory_Type(sType);
// To retrieve values
String sCategory = data.getCategory();
String sType = data.getCategory_Type();

Custom ArrayList, Passing data between Classes

I have a fragment activity with a custom arraylist format
public class giftsListFormat {
String id;
String name;
String url;
String points;
}
ArrayList<giftsListFormat> giftList = new ArrayList<giftsListFormat>();
I am trying to access this list format from an asynctask class
private static class MyAsyncTask extends AsyncTask<Void, Void, Void> {
private MyAsyncTask () {
[How can i create an object of giftsListFormat here?]
[How can i access giftList from here]
}
}

Try this - This may be the custom class that you need.
Declare this as global :
ArrayList<giftsListFormat> details = new ArrayList<giftsListFormat>();
public class giftsListFormat {
String id;
String name;
String url;
String points;
public String getid() {
return id;
}
public void setid(String id)
{
this.id = id;
}
public String getname() {
return name;
}
public void setname(String name)
{
this.name = name;
}
public String geturl() {
return url;
}
public void seturl(String url)
{
this.url = url;
}
public String getpoints() {
return points;
}
public void setpoints(String points)
{
this.points = points;
}
}
To put the value into the array list - Do this
giftsListFormat Detail;
Detail = new giftsListFormat();
Detail.setid("test1");
Detail.setname("test2");
details.add(Detail);
Now to retrieve the values
put the following code inside the async task
details.get(i).id.toString();
details.get(i).name.toString();
details.get(i).url.toString();
You can iterate over the size of the array list.
details.size();

Make "giftList" global variable in your activity.
Send the context to your AsyncTask through Constructor.
Now you can access that variable as follows:
private static class MyAsyncTask extends AsyncTask<Void, Void, Void> {
ArrayList<giftsListFormat> giftList;
private MyAsyncTask (Activity activity) {
giftList = activity. giftList;
giftsListFormat ref = giftList.get(pos);
}
}

create a giftsListFormat class like:
public class giftsListFormat{
String id;
String name;
String url;
String points;
//create constructure and assign parameters which you want to set
public giftsListFormat(String id, String name,String url, String points){
this.id = id;
this.name = name;
this.url = url;
this.points = points;
}
public getId(){
return id;
}
public getName(){
return name;
}
public getUrl(){
return url;
}
public getPoints(){
return points;
}
}
And use this class like: ArrayList<giftsListFormat>...
Inside AsyncTask set all your data at the time of initialization..like:
giftsListFormat mData = new giftsListFormat(id, name, url, points);
And when you want to get just use get methods...

Pass object that contains objects to Activity via Intent

I have an Object that I need to pass via the Intent to another Activity via the onclick method.
I was following this answer here How to send an object from one Android Activity to another using Intents?
Which works fine however my Object has within it an Array of objects.
How do I pass this object with its Array of Objects?
Below are the classes before using Parcelable
List (the object to be passed)
public class List {
private String Name;
private ArrayList<ListItem> items;
public List(){
items = new ArrayList<ListItem>();
}
public void addItem(String title, String d, String s, int p){
ListItem i = new ListItem();
i.setDecription(d);
i.setPrice(p);
i.setSite(s);
i.setTitle(title);
items.add(i);
}
public String getName() {
return Name;
}
public void setName(String Name) {
this.Name = Name;
}
public int getCount() {
return items.size();
}
public ArrayList<ListItem> getList(){
return items;
}
}
ListItem
public class ListItem {
private String title;
private String decription;
private String site;
private int price;
public void setTitle(String title) {
this.title = title;
}
public void setDecription(String d){
this.decription = d;
}
public void setSite(String s){
this.site = s;
}
public void setPrice(int i){
this.price = i;
}
public String getTitle(){
return title;
}
public String getDecription(){
return decription;
}
public String getSite(){
return site;
}
public int getPrice(){
return price;
}
}
So how would I use Parcelable on List to send the ArrayList as well.
THank you and if you need any more info please ask!

You're trying to pass around data that shouldn't normally be passed around. A list is an ideal candidate for an SQLite Database. Try that or another way to persist data in android: http://developer.android.com/guide/topics/data/data-storage.html
If you insist on using Parcelable:
How can I make my custom objects Parcelable?
Also don't use List as your own type, it's standard JAVA.