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Custom adapter's asynchronous behaviour

I have created my own custom adapter class in my android app and I am calling it from one of my activity. I am adding some elements to the view from the adapter class and I need to access those variables from my activity class.
Now, ideally I would expect it to fill the view and then execute the further code in my activity class, but adapter class is taking some time to populate the view and in the meanwhile further code in my activity class is getting executed where no such elements have been added yet.
How do I handle this situation? I come from a js background. Do we have something like promises in java?
According to the answers I have my changed my code to this:
public class HomeActivity extends Activity {
GridView grid;
String text[] = {"Calendar","Uber","Weather","News","Youtube","Clock","Email","Maps","Twitter","Facebook"};
String list_app_name[] = {"calendar","uber","weather","news","youtube","clock","email","maps","twitter","facebook"};
String id_button[] = {"button_calendar","button_uber","button_weather","button_news","button_youtube","button_clock","button_email","button_maps","button_twitter","button_facebook"};
int image[] = {R.drawable.social_icons1,R.drawable.social_icons2,R.drawable.social_icons3,R.drawable.social_icons4,
R.drawable.social_icons5,R.drawable.social_icons6, R.drawable.social_icons7,R.drawable.social_icons8,
R.drawable.social_icons9,R.drawable.social_icons10};
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mDrawerToggle;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_home);
//setting up the adapter for gridView
grid = (GridView)findViewById(R.id.simpleGrid);
ImageAdapter ia = new ImageAdapter(this,image,text,id_button);
grid.setAdapter(ia);
ia.notifyDataSetChanged();
try {
initStateOfApps();
} catch (JSONException e) {
e.printStackTrace();
}
}
public void initStateOfApps() throws JSONException {
Log.d("here","here");
ArrayList<String> list = getEnabledApps();
Log.d("apps",list.toString());
for(int i=0;i<list.size();i++) {
String app_name = list.get(i);
ToggleButton button=null;
if(app_name.equals("calendar")) {
button = (ToggleButton)findViewById(R.id.button_calendar);
button.setChecked(true);
}
}
}
}
So what is happening is that I am creating some toggle buttons that are getting populated in the ImageAdapter class that I wrote.
Once the ImageAdapter is called, I call the notifydatasetchanged() on the adapter in order to update the view.
What I am doing inside the adapter is giving each of the toggle buttons some custom ID I wrote in res/values/ids.xml.
After using setId on each of the toggle buttons, I try using that ID in my activity class but it gives me nullPointerException in the initStateOfApps() where I am trying to change the state of button.
So even after using the notifyDataSetChanged it is still behaving the same.
ImageAdapter.java
public class ImageAdapter extends BaseAdapter {
private Context context;
private final int item_image[];
private final String item_text[];
private final String button_id[];
public ImageAdapter(Context context, int item_image[], String[] item_text,String[] button) {
this.context = context;
this.item_image = item_image;
this.item_text = item_text;
this.button_id = button;
}
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View gridView;
if (convertView == null) {
gridView = new View(context);
// get layout from custom_gridview.xml
gridView = inflater.inflate(R.layout.item, null);
// set value into imageview
final ImageView image = (ImageView) gridView.findViewById(R.id.item_image);
image.setImageResource(item_image[position]);
// set value into textview
TextView text = (TextView) gridView.findViewById(R.id.item_text);
text.setText(item_text[position]);
final ToggleButton button_ = (ToggleButton) gridView.findViewById(R.id.item_button);
if(position==0) {
button_.setId(R.id.button_calendar);
image.setId(R.id.image_calendar);
}
button_.setOnCheckedChangeListener( new CompoundButton.OnCheckedChangeListener()
{
#Override
public void onCheckedChanged(CompoundButton toggleButton, boolean isChecked)
{
if(context.getResources().getResourceEntryName(toggleButton.getId()).equals("button_calendar")) {
if(isChecked) {
try {
setStateOfApp("calendar","true");
} catch (JSONException e) {
e.printStackTrace();
}
Intent intent = new Intent(context, GoogleApp.class);
((Activity) context).startActivityForResult(intent,10);
} else {
try {
setStateOfApp("calendar","false");
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
}
} else {
gridView = (View) convertView;
}
return gridView;
}
}

You are trying to access View which is not a part of Activity's content view. So you can't access that view directly.
button = (ToggleButton)findViewById(R.id.button_calendar); // will return null
This ToggleButton will be null because findViewById will fail to find out ToggleButton in current content view because that view is present in your Adapter not in content view.
And you are getting nullpointerException because you are trying to access property on null view.
button.setChecked(true); // This button is null

In java we have <Future>, but I don't think it's what you're looking for.
The adapter (extending BaseAdaper) behaviour lets you create the adapter and, even in a second moment, change underlying data via getAdapter().setData() or whatever method you choose to add.
From this perspective, the adapter is a "stupid" component acting as A View containers, you should retrieve data elsewhere (CursorAdapter is different).
So, in your Activity, fill the adapter with needed data and, when finished, call adapter.notifyDatasetChanged(). This will inform the adapter that its own data has changed and it must refresh views

Yes, ideally, the population of the adapter should be coming from the outside. The adapter should really just take in a list of data and map that data to the views. For example, some method or task in the Activity could produce a list of data (probably asynchronously...since you mentioned it) that you then pass into the adapter and then you can notifyDataSetChanged() if you need to.
I can't see your code, but if for some reason the data is truly required to be populated from inside the adapter, you could use an event bus and subscribe to it in the Activity. I would recommend going with the first option, but here are some links if you choose to use an event bus:
https://github.com/greenrobot/EventBus
http://square.github.io/otto/

As per my understanding with your question
You are not properly managed the adapter data in your activity.
If any of the data or code interlinked with your adapter data or values
Then you can start those code after you retrieve the values or data and update the view in your activity.
Please note that use Viewholders in adapter to avoid slow populating and scrolling in listviews.
Viewholders will smooth your process.
I personally suggest you that
Please go with Recyclerview and RecyclerViewAdapter.
So many Android developers are using it.
If you have background tasks in adapter you can prefer to use RX Java or EventBus
If you provide the code
It's better for us to suggest exact solution

What is notifyItemRangeChanged(0, this.data.size()); in this example and how does it work?

I understand how a ViewHolder's onBindViewHolder works, however I'm unclear about how notifyItemRangeChanged(0, this.data.size()); works in this example and what it does exactly.
The data that is supplied to this adapter is in Json format.
The adapter is below:
public class AdapterQuestion extends RecyclerView.Adapter<AdapterQuestion.ViewQuestion>{
private LayoutInflater mLayoutInflater;
//this is an arrayList of questionData objects
private ArrayList<QuestionData> data =new ArrayList<>();
//Created the layoutInflator
public AdapterQuestion(Context context){
//get from context
mLayoutInflater=LayoutInflater.from(context);
}
public void setBloglist(ArrayList<QuestionData> data){
this.data =data;
notifyItemRangeChanged(0, this.data.size());
}
#Override
public ViewQuestion onCreateViewHolder(ViewGroup parent, int viewType) {
//inflates the customQuestion view or converts it to java code
View view= mLayoutInflater.inflate(R.layout.customquestion, null);
//We now want to convert the View into a ViewQuestion, view Question takes
//a view so we pass the view into view question and then return it.
ViewQuestion holder=new ViewQuestion(view);
return holder;
}
//ViewGroup parent and ViewType are not being assigned.
#Override
public void onBindViewHolder(ViewQuestion holder, int position) {
//here we need to bind the data to our view, there is currently no Data!
//We need to get the data from our JSON
//Parameters is a ViewHolder and a Position
//This gives us the current information object from the whole arraylist
//data.get(position) data is the arraylist and we are getting the current position or index;
//That current obj is of Type QuestionData
QuestionData currentObj= data.get(position);
//we are accessing the Inflated view, or saved view with holder
//holder.answerText is the textView in holder. We are then taking that current object
//We are getting the text of the current object and setting it to the AnswerText view
holder.answerText.setText(currentObj.getMtext());
holder.answerId.setText(currentObj.getId());
holder.mVotes.setText(currentObj.getVotes());
holder.mLikeButton.setTag(currentObj);
}
#Override
public int getItemCount() {
return data.size();
}
public class ViewQuestion extends RecyclerView.ViewHolder{
//once we create it once the reclycer view will automatically recycle it
private TextView answerText;
private TextView answerId;
private TextView mVotes;
private LikeButton mLikeButton;
public ViewQuestion (View itemView){
super(itemView);
//here we are finding the views by their ID
answerText=(TextView)itemView.findViewById(R.id.answerText);
answerId=(TextView)itemView.findViewById(R.id.answerId);
mVotes=(TextView)itemView.findViewById(R.id.VoteTextView);
mLikeButton= (LikeButton)itemView.findViewById(R.id.heart_buttons);
mLikeButton.setOnLikeListener(new OnLikeListener() {
#Override
public void liked(LikeButton likeButton) {
Voting vote = new Voting();
vote.onUpVote(convertToString(),
getAdapterPosition(),ViewQuestion.this);
System.out.print("Adapter Position"+getAdapterPosition());
}
#Override
public void unLiked(LikeButton likeButton) {
Voting onDown=new Voting();
onDown.onDownVote(convertToString(),
getAdapterPosition(), ViewQuestion.this);
}
});
}
public String getVoteView(){
String voteView=mVotes.getText().toString();
return voteView;
}
public String convertToString(){
String converted=answerId.getText().toString();
return converted;
}
public int convertToInt(){
String converted=answerId.getText().toString();
int ConvertedInt=Integer.parseInt(converted);
return ConvertedInt;
}
}
}

When the data that is to be set in RecyclerView is changed, the Adapter needs to get notified of the data change so that it can change the data in recyclerview.
The method
notifyItemRangedChanged(fromIndex,toIndex);
is used to notify the adapter that some set of data is changed among the whole data and it tells the adapter that adapter should refresh the data and reload it into the recyclerView starting from fromIndex to toIndex as passed into the method .
use this method if you have multiple data changed but not all , those changed data also are in cluster so that you can say from 5th to 10th index data are changed .
If all data are changed call :
notifyDataSetChanged();
if only one dataItem is changed then call :
notifyItemChanged(dataPosition);

Using notifyItemRangeChanged(0, this.data.size()) it’s bad practice.
Best way is using notifyItemChanged or notifyItemRangeChanged with payload.
Payload - optional parameter (key). That give you opportunity to check what kind of update do you need.
public void onBindViewHolder(/*...*/, List payloads) {
if (payloads.isEmpty()) {
setText(holder, position);
downloadBitmap(holder, position);
} else if (payloads.contains(SET_ONLY_TEXT)){
setText(holder, position);
}
}
In this example payloads used for checking when adapter should update only the text.

in your case you are not doing it(notifyItemRangeChanged) right as you might as well can call notifyDataSetChanged(); because you are telling the adapter that the entire list has changed and not specific position.

add row to section in recyclerView

I have a RecyclerView inside that recyclerView I added two Sections Favorites, All Contacts. For adding the section I used SimpleSectionedRecyclerViewAdapter
now I have rows with section which is hardcoded (the index of rows and section), I want to add rows to favorite section by selecting the rows since there's nothing documented about what I want, I don't know where to start or what I have to do ?
If anybody knows how can I add a row from All Contacts section (which is default location for rows ) by selecting them. then please give me some hints for what I have to do
what I want is something like this :
add to favorite by pressing the button
any guidance will be so helpful for me , thanks

You can achieve it with the library SectionedRecyclerViewAdapter without having to hardcode header/rows indexes.
First create a Section class to group your items:
class MySection extends StatelessSection {
String title;
List<String> list;
public MySection(String title, List<String> list) {
// call constructor with layout resources for this Section header, footer and items
super(R.layout.section_header, R.layout.section_item);
this.title = title;
this.list = list;
}
#Override
public int getContentItemsTotal() {
return list.size(); // number of items of this section
}
#Override
public RecyclerView.ViewHolder getItemViewHolder(View view) {
// return a custom instance of ViewHolder for the items of this section
return new MyItemViewHolder(view);
}
#Override
public void onBindItemViewHolder(RecyclerView.ViewHolder holder, int position) {
MyItemViewHolder itemHolder = (MyItemViewHolder) holder;
// bind your view here
itemHolder.tvItem.setText(list.get(position));
}
#Override
public RecyclerView.ViewHolder getHeaderViewHolder(View view) {
return new SimpleHeaderViewHolder(view);
}
#Override
public void onBindHeaderViewHolder(RecyclerView.ViewHolder holder) {
MyHeaderViewHolder headerHolder = (MyHeaderViewHolder) holder;
// bind your header view here
headerHolder.tvItem.setText(title);
}
}
Then you set up the RecyclerView with your Sections:
// Create an instance of SectionedRecyclerViewAdapter
SectionedRecyclerViewAdapter sectionAdapter = new SectionedRecyclerViewAdapter();
// Create your sections with the list of data
MySection favoritesSection = new MySection("Favorites", favoritesList);
MySection contactsSection = new MySection("Add Favorites", contactsList);
// Add your Sections to the adapter
sectionAdapter.addSection(favoritesSection);
sectionAdapter.addSection(contactsSection);
// Set up your RecyclerView with the SectionedRecyclerViewAdapter
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setAdapter(sectionAdapter);
You can find an example of how to listen to the button click here.
You can also add new rows to your sections without having to recalculate indexes, just create a method like this in your Section class:
public void addRow(String item) {
this.list.add(item);
}
Then:
favoritesSection.addRow("new item");
sectionAdapter.notifyDataSetChanged();

Arraylist custom location

I have an arraylist and I want to update specific item.I am adding data to list with this line:
randomsList.add(new Random(result.get(i).getAsJsonObject(),0));
This is adding datas to 0,1,2,3,4... locations so when I try to update an item I don't know which object is where.
I am updating data with this line:
randomsList.set(position,new Random(user,1));
I think if I use the custom numbers for location I can update specific item.My prototype:
randomsList.add({USER_ID},new Random(result.get(i).getAsJsonObject(),0));
And if I want to update it then I use this line:
randomsList.set({USER_ID},new Random(user,1));
Is this a good approach ? If your answer is no,how should be ?
P.S. : I am using this arraylist with an adapter

As #itachiuchiha mentions, you should use a Map. The "custom numbers" you mention are your key (integers), and the value is the Random object.
As an aside, in response to your comment, below is an example of an Android Adapter that uses a Map as the underlying datasource.
public class RandomsAdapter extends BaseAdapter {
private Map<Integer, Random> randoms;
public RandomsAdapter(Map<Integer, Random> randoms) {
this.randoms = randoms;
}
public void updateRandoms(Map<Integer, Random> randoms) {
this.randoms = randoms;
notifyDataSetChanged();
}
#Override
public int getCount() {
return randoms.size();
}
#Override
public Random getItem(int position) {
return randoms.get(position);
}
#Override
public long getItemId(int position) {
// we won't support stable IDs for this example
return 0;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View view = convertView;
if (view == null) {
view = createNewView();
}
update(view, songs.get(position));
return view;
}
private View createNewView() {
// TODO: create a new instance of your view and return it
return null;
}
private void update(View view, Random random) {
// TODO: update the rest of the view
}
}
Note the updateRandoms(Map<Integer, Random> randoms) method.
While you could expose a method in the adapter to update a single entry in the Map, it shouldn't be the responsibility of the Adapter to handle modifications to the map. I prefer passing the entire map again - it could still be a reference to the same object, but the Adapter doesn't know or care; it just knows: "my underlying datasource has been changed/modified, I need to tell my observers that they should refresh their views by calling notifyDataSetChanged()".
Alternatively, you could call notifyDataSetChanged() on the adapter externally when you modify the underlying Map (this tells the ListView that its data is out of date and to request its views from the adapter again).

Android BaseAdapters & Multiple Listviews

I am currently creating a basic news aggregator app for Android, I have so far managed to create multiple HorizontalListViews derived from this: http://www.dev-smart.com/archives/34
I am parsing all data from live JSON objects and arrays.
The process goes something like this:
1) Start app
2) Grab a JSON file which lists all feeds to display
3) Parse feed titles and article links, add each to an array
4) Get number of feeds from array and create individual HorizontalListView for each. i.e. "Irish Times".
5) Apply BaseAdapter "mAdapter" to each HorizontalListView during creation.
My baseadapter is responsible for populating my HorizontalListViews by getting each title and thumbnail.
My problem is however that all my feeds seem to contain the same articles and thumbnails. Now I am only new to Android so I'm not 100% sure whats going wrong here. See screenshot below.
Do I need to create a new BaseAdaptor for each HorizontalListview or can I use the same one to populate all my listviews with unique data.
Here's some code to help explain what I mean:
1) OnCreate method to get JSON data, parse it, get number of feeds and create each HorizontalListView
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.listviewdemo);
//--------------------JSON PARSE DATA------------------
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
String json = jParser.getJSONFromUrl(sourcesUrl);
//Parse feed titles and article list
getFeeds(json);
//Create Listviews
for(int i = 0; i < feedTitle.size()-1; i++){
//getArticleImage(i);
addHorzListView(i);
articleArrayCount++;//Used to mark feed count for adaptor to know which array position to look at and retrieve data from.
//Each array position i.e. [1] represents a HorizontalListview and its related articles
}
}
2) addHorzListView method, used to create HorizontalListView and apply adaptor
//Method used to dynamically add HorizontalListViews
public void addHorzListView(int count){
LinearLayout mainLayout = (LinearLayout) findViewById(R.id.main_layout);
View view = getLayoutInflater().inflate(R.layout.listview, mainLayout,false);
//Set lists header name
TextView header = (TextView) view.findViewById(R.id.header);
header.setText(feedTitle.get(count));
//Create individual listview
HorizontalListView listview = (HorizontalListView) view.findViewById(R.id.listviewReuse);
listview.setAdapter(mAdapter);
//add listview to array list
listviewList.add(listview);
mainLayout.addView(view, count);
}
3) Baseadaptor itself:
private BaseAdapter mAdapter = new BaseAdapter() {
private OnClickListener mOnButtonClicked = new OnClickListener() {
#Override
public void onClick(View v) {
AlertDialog.Builder builder = new AlertDialog.Builder(HorizontalListViewDemo.this);
builder.setMessage("hello from " + v);
builder.setPositiveButton("Cool", null);
builder.show();
}
};
#Override
public int getCount() {
return noOfArticles.length;
}
#Override
public Object getItem(int position) {
return null;
}
#Override
public long getItemId(int position) {
return 0;
}
//Each listview is populated with data here
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View retval = LayoutInflater.from(parent.getContext()).inflate(R.layout.viewitem, null);
TextView title = (TextView) retval.findViewById(R.id.title);
title.setText(getArticleTitle(position));
new DownloadImageTask((ImageView) retval.findViewById(R.id.ImageView01)) .execute(getArticleImage(position));
Button button = (Button) retval.findViewById(R.id.clickbutton);
button.setOnClickListener(mOnButtonClicked);
return retval;
}
};
The adapter mAdapter is currently displaying the articles from the last HorizontalListView that calls it.
Currently I am using the same BaseAdaptor for each ListView as I figured it populated the listview as soon as its called but i looks as though a BaseAdaptor can only be called once, I really dont know.
I want to dynamically populate feeds though without having to create a new Adaptor manually for each HorizontalListView.
Any help would be much appreciated.

So...you got the same info in 4 listview, right? In that case you only need oneAdapter populating 4 listview.
An adapter just provide the views which are visible in that moment to the listview (if it is implemented in the right way) so you can reuse the adapter if the info contained is the same.