Develop Reference

RecyclerView adding Item onclickListener() + timers optimization

I want to add an onClickListener to items in my RecyclerView. I added the listener in the Holder class as follows:
public class Holder extends RecyclerView.ViewHolder {
TextView firstName;
TextView lastName;
public Holder (final View itemView) {
super(itemView);
firstName = itemView.findViewById(R.id.firstName );
lastName= itemView.findViewById(R.id.lastName);
itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//Do work
}
}
}
But, I think this will cause the scrolling of the list to be a little jerky and not perfectly smooth specially on old devices.
Question 1:
Is there a better way to do that? Or how can I optimize my code?
Question 2:
I intend to add a dynamically changing variable for each item in the list such as a timer, and I don't want the scrolling to be too slow! How should I update the timers the best way?

Create a member variable for item OnClickListener and set it in Holder's constructor.It will be one listener in your adapter when app is running.

Jerky Scrolling
Since you are using RecyclerView I don't think that you will face any issue with scrolling because RecyclerView inherently comes with ViewHolder Pattern. (In case of Simple listView you have to make ViewHolder to avoid jerky scrolling)
Code improvement
Instead of adding a Listener in ViewHolder, make it a Class variable in your RecyclerView Adapter.
There is a standard way to add a Listener in RecyclerView
Create a listener
interface ClickListener{
void click();
}
implement this listener to Your Activity
YourActivity implements ClickListener{
}
Typecast this listener in Your Adapter
YourAdapter extends RecyclerView.Adapter<YourAdapter.Holder>{
ClickListener listener;
public YourAdapter(Context context)
{
this.context = context;
listener = (ClickListener)context;
}
public class Holder extends RecyclerView.ViewHolder {
TextView firstName;
TextView lastName;
public Holder (final View itemView) {
super(itemView);
firstName = itemView.findViewById(R.id.firstName );
lastName= itemView.findViewById(R.id.lastName);
}
// Item Click listener goes here.
#Override
public void onBindViewHolder(DownLoadViewHolder holder, final int position) {
// Do something
listener.click();
}
}
Just giving you the overview.
You can see THIS for reference.

Saving SwitchCompat State in the recycler view while scrolling

I have a recyclerview which its items contain textView and switchCompat. And in the same activity I have also a textView that have a numerical value in it. The task is when the switchCompat turned on the text view above the recyclerview which contain the numerical value should increase by the value in the recyclerview item textview. I already did that but when scrolling in the recyclerview the switchCompat back to the default state and the value of the numerical textview backs to its old value,
Any help with that?
I Apology for not being able to post a part of the code now and I'll do this as soon as i can, I just posted it now in case anyone pass through something like this before
Thank you

The key to a recycler view or any adapter view in Android is to have the adapter adapt your models to the view. In your case your view is a TextView plus a Switch, so your adapter must adapt some model to this view. In this case I'd choose a simple model like this:
class ItemModel {
String text;
boolean on;
}
I've omitted getters and setters for simplicity
This model contains an string text which reflects the text in your text view and a boolean on that reflects the state of the switch. When true the switch is checked and when false it's unchecked.
There's tons of ways to represent this model. I've chosen this one, you may choose a different one. The point is, you need to save the state somewhere and this is what I mean by model - the view model.
Now let's build an adapter that can do 2 things - Update the models when the switch is clicked and tell the activity that the switch changed state. Here's one way to do this:
public class ItemsAdapter extends
RecyclerView.Adapter<ItemsAdapter.ViewHolder> {
#NonNull
private final List<ItemModel> itemModels;
#Nullable
private OnItemCheckedChangeListener onItemCheckedChangeListener;
ItemsAdapter(#NonNull List<ItemModel> itemModels) {
this.itemModels = itemModels;
}
#NonNull
#Override
public ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
return new ViewHolder(LayoutInflater.from(parent.getContext())
.inflate(R.layout.item, parent, false));
}
#Override
public void onBindViewHolder(#NonNull final ViewHolder holder, int position) {
ItemModel item = itemModels.get(position);
holder.text.setText(item.text);
holder.switchCompat.setChecked(item.on);
// Make sure we update the model if the user taps the switch
holder.switchCompat.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
int adapterPosition = holder.getAdapterPosition();
ItemModel tapped = itemModels.get(adapterPosition);
itemModels.set(adapterPosition, new ItemModel(tapped.text, isChecked));
if (onItemCheckedChangeListener != null) {
onItemCheckedChangeListener.onItemCheckedChanged(adapterPosition, isChecked);
}
}
});
}
#Override
public void onViewRecycled(#NonNull ViewHolder holder) {
super.onViewRecycled(holder);
holder.switchCompat.setOnCheckedChangeListener(null);
}
#Override
public int getItemCount() {
return itemModels.size();
}
public void setOnItemCheckedChangeListener(#Nullable OnItemCheckedChangeListener onItemCheckedChangeListener) {
this.onItemCheckedChangeListener = onItemCheckedChangeListener;
}
interface OnItemCheckedChangeListener {
/**
* Fired when the item check state is changed
*/
void onItemCheckedChanged(int position, boolean isChecked);
}
class ViewHolder extends RecyclerView.ViewHolder {
TextView text;
SwitchCompat switchCompat;
ViewHolder(View itemView) {
super(itemView);
text = itemView.findViewById(R.id.item_text);
switchCompat = itemView.findViewById(R.id.item_switch);
}
}
}
There's a lot to digest, but let's focus on the important bits - the method onBindViewHolder. The first 3 lines are the classic recycling of the view. We grab the model at the correct position and set the elements in the view that correspond to model's attributes.
Then it gets more interesting. We set a OnCheckedChangeListener to update the model and the activity every time the switch changes state. The first 3 lines change the model in the adapter and the rest uses the custom interface OnItemCheckedChangeListener to notify the listener about the switch change. It's important to notice that inside the method OnCheckedChangeListener you should no longer use position, but rather use holder.getAdapterPosition. This will give you the correct position in the adapter's data list.
Since now the adapter has always the correct models inside the data list, every time the method onBindViewHolder is called the adapter knows exactly how to setup the view. This means that while scrolling and recycling the views, it will preserve the state of each item within the models inside the data list.
It's important to remove the OnCheckedChangeListener when the view gets recycled - onViewRecycled. This avoids messing the count when the adapter is setting the value of switchCompat in the onBindViewHolder.
Here's an example of how the activity could look like:
public class MainActivity extends AppCompatActivity {
private int count = 0;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
List<ItemModel> data = new ArrayList<>();
for (int i = 1; i <= 100; i++)
data.add(new ItemModel("Item " + i, false));
ItemsAdapter adapter = new ItemsAdapter(data);
((RecyclerView) findViewById(R.id.recyclerview)).setAdapter(adapter);
final TextView countTextView = findViewById(R.id.count);
drawCount(countTextView);
adapter.setOnItemCheckedChangeListener(new ItemsAdapter.OnItemCheckedChangeListener() {
#Override
public void onItemCheckedChanged(int position, boolean isChecked) {
if (isChecked)
count++;
else
count--;
drawCount(countTextView);
}
});
}
private void drawCount(TextView countTextView) {
countTextView.setText(String.valueOf(count));
}
}
This code is meant to demonstrate the idea, not to follow :) In any case, we setup all the initial state and then set up the custom listener OnItemCheckedChangeListener to update the text view in the activity.
The layout files shouldn't be relevant here, but as you can imagine the activity has a text view with id count and there's a recycler view with the id recyclerview.
Hope this helps

It solved for me after adding the below method to the adapter:
#Override
public int getItemViewType(int position) {
return position;
}

How to change an image in a ListView, when the image is clicked?

EDIT: I've solved this issue, if interested, please take a look at my answer to see how I did it!
I am currently working in Android Studio. I have a ListView that I populate with several items. Within each of these items is an ImageButton that has a "+" as the image. What I want to do is, whenever that image is clicked (not the entire ListView item, just the image), I want that image of "+" to become another image. Any help would be appreciated, as this has been an ongoing issue for a while!
Here is the current code that I attempt to use to achieve this:
final ImageButton movieSeen = (ImageButton convertView.findViewById(R.id.movieWatched);
movieSeen.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
movieSeen.setImageResource(R.drawable.ic_check_circle_black_24dp);
}
});
Currently this does update the image that I click correctly, BUT it also updates images that are not yet rendered on the screen, so when I scroll the list view down, other objects are also changed to ic_check_circle_black_24dp.
What I want is pretty straightforward, I just don't know how to achieve it. I just want to click an ImageButton, that's inside an item on a ListView, and have that ImageButton change its image resource.
Here is my custom array adapter as requested!
private class MovieScrollAdapter extends ArrayAdapter<Movie> {//custom array adapter
private Context context;
private List<Movie> movies;
public MovieScrollAdapter(Context context, List<Movie> movies){
super(context, -1, movies);
this.context = context;
this.movies = movies;
if(this.movies.isEmpty()){//if no results were returned after all processing, display a toast letting the user know
Toast.makeText(getApplicationContext(), R.string.no_matches, Toast.LENGTH_SHORT).show();
}
}
#Override
public View getView(final int position, View convertView, ViewGroup parent){
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) context.
getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.movie_layout, parent, false);
}
TextView title = (TextView) convertView.findViewById(R.id.title);
title.setText(movies.get(position).getTitle());
TextView plot = (TextView) convertView.findViewById(R.id.plot);
plot.setText(movies.get(position).getPlot());
TextView genre = (TextView) convertView.findViewById(R.id.genre);
genre.setText(movies.get(position).getGenre());
TextView metaScore = (TextView) convertView.findViewById(R.id.metascore);
if(movies.get(position).getMetaScore() == -1){//if the metaScore is set to -1, that means movie has not been rated, which by inference means it is not yet released
metaScore.setText(R.string.movie_not_released);
metaScore.setTextSize(TypedValue.COMPLEX_UNIT_SP, 9.5f);//smaller text so it fits without breaking anything
metaScore.setTextColor(getColor(R.color.colorAccent));
} else {
metaScore.setText(" " + Integer.valueOf(movies.get(position).getMetaScore()).toString() + " ");//using white space for minor formatting, instead of altering margins each time this is rendered
metaScore.setTextSize(TypedValue.COMPLEX_UNIT_SP, 25);
//setting up a "highlighted" background to achieve metacritic square effect
Spannable spanText = Spannable.Factory.getInstance().newSpannable(metaScore.getText());
spanText.setSpan(new BackgroundColorSpan(getColor(R.color.metaScore)), 3, 7, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
metaScore.setText(spanText);
metaScore.setTextColor(getColor(android.R.color.primary_text_dark));
}
ImageView image = (ImageView) convertView.findViewById(R.id.imageView);
new ImageDownloadTask((ImageView)image).executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, movies.get(position).getPosterURL());//because there are several images to load here, we let these threads run parallel
title.setOnClickListener(new View.OnClickListener() {//setting up a simple onClickListener that will open a link leading to more info about the movie in question!
#Override
public void onClick(View v) {
Uri uri = Uri.parse(movies.get(position).getMovieURL());
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);
}
});
final ImageButton movieSeen = (ImageButton) convertView.findViewById(R.id.movieWatched);
movieSeen.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
movieSeen.setImageResource(R.drawable.ic_check_circle_black_24dp);
}
});
return convertView;
}
}

The problem is on a ListView, the views are being reused to save memory and avoid creating a lot of views, so when you change a view it keeps the state while it's being reused to show another item.
For example, you have 100 elements, you touch the first element ImageButton and that button is changed. Maybe on the screen there are 5 elements of the list showing, and you changed the first one. But if you scroll to the element number 15 the system is not creating 15 views, is taking the first one you clicked before and is changing the content.
So, you are expecting to have a view with a "+" ImageButton icon but you see another icon, that's because you must keep the view state inside a model object and set the state every time 'getView' is called.
Post your list adapter to see how is implemented.
UPDATE:
Now I see your adapter implementation I suggest you to add an int field inside Movie class to save the resource id you want to show on the ImageButton. Then inside the onClickListener you must set to this field the resource you want to show on the view when its clicked, and call notifyDataSetChanged(). After that you must do inside getView():
movieSeen.setImageResource(movies.get(position).getButtonImageResource());

Use RecyclerView and set the OnItemClickListener on your ImageButton within your view holder.
This already answered question should help.
The adapted code below is coming from this nice tutorial. Using ReciclerView with an adapter like this will solve your concern.
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private ArrayList<String> mDataset;
public class ViewHolder extends RecyclerView.ViewHolder {
public ImageView imageView;
public TextView txtHeader;
public ViewHolder(View v) {
super(v);
txtHeader = (TextView) v.findViewById(R.id.xxx);
imageView = (ImageView) v.findViewById(R.id.yyy);
}
}
public MyAdapter(ArrayList<String> myDataset) {
mDataset = myDataset;
}
#Override
public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.rowlayout, parent, false);
ViewHolder vh = new ViewHolder(v);
return vh;
}
// Replace the contents of a view (invoked by the layout manager)
#Override
public void onBindViewHolder(ViewHolder holder, int position) {
final String name = mDataset.get(position);
holder.txtHeader.setText(mDataset.get(position));
holder.imageView.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// Do here what you need to change the image content
}
});
holder.itemView.setBackground(....); // Initialize your image content here...
}
//...
}

Here is my suggestion to achieve what you want :
Create An Interface in your adapter :
public interface YourInterface{
void selectedImage(int position,ImageView iamgeView);
}
Create variable interface in your adapter that you just created :
private YourInterface yourInterface;
and make your adapter constructor like this :
public YourAdapterConstructor(YourInterface yourInterface){
this.yourInterface = yourInterface;
}
in your ImageView onClickListener :
final ImageButton movieSeen = (ImageButton) convertView.findViewById(R.id.movieWatched);
movieSeen.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
yourInterface.selectedImage(position, imageView);
}
});
and then finally in your class activity, Implements YourInterface and change you ImageView there :
#Override
public void selectedImage(final int position,final ImageView imageView) {
//change your image view here
}

I'd like to thank everyone for their support. Unfortunately, with the way my code is written (rather messily and without much regard for what my professors taught me), I was unable to get most of these solutions to work. I did however, find a solution that falls in line with my own framework that I've had going into this. Unfortunately I could not redo my entire adapter method, or implement various interfaces that would cause me to have to rewrite a huge chunk of code for something seemingly trivial.
So, if anyone finds themselves in this situation in the future, here is my solution:
In the Movie class, I add a boolean value that represents my values, along with some getters and setters:
private boolean watchedStatus;
public boolean hasSeen() {return watchedStatus;}
public void toggleWatchedStatus(){
watchedStatus = !watchedStatus;
}
In the getView method, I simply get a reference to the ImageButton, and then based on the boolean value returned by "hasSeen," I set the ImageResource to one of two states:
#Override
public View getView(final int position, View convertView, ViewGroup parent){
ImageButton movieSeen = (ImageButton) convertView.findViewById(R.id.movieSeen);
if(movies.get(position).hasSeen()){
movieSeen.setImageResource(R.drawable.ic_check_circle_black_24dp);
} else {
movieSeen.setImageResource(R.drawable.ic_add_circle_black_24dp);
}
}
Next, I override the OnClickListener, and make it so that whenever the button is clicked, the boolean value in the Movie.java class is toggled. The key here was using the ArrayAdapter's method "notifyDataSetChanged()" This completes the process, and lets the ListView know that it should update itself:
final ImageButton movieSeenForClick = (ImageButton) convertView.findViewById(R.id.movieSeen);
movieSeen.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//movieSeenForClick.setImageResource(R.drawable.ic_check_circle_black_24dp);
movies.get(position).toggleWatchedStatus();
System.out.println(movies.get(position).hasSeen() + " ------- position: " + position);
notifyDataSetChanged();
}
});
Thanks again for the time taken to provide information, a lot of it really did steer me int he right direction, I just had to use the information correctly with the way my code was structured.

Why does OnClickListener on a ViewHolder don't work?

I'm trying to implement a way to handle item selection on a RecyclerView. I personally don't like the way suggested in some answers on SO of passing through gestures, and I thought that implementing an OnClickListener, as suggested here and here, was waaay cleaner.
The fact is that... this pattern doesn't actually work! I'm really not able to understand why my OnClickListener.onClick is never called. It's kinda like another method intercepts the click before onClick can take care of it.
This is my code:
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
TextView tvName;
ImageView star;
public ViewHolder(View itemView) {
super(itemView);
tvName = (TextView) itemView.findViewById(R.id.CHAT_ITEM_name);
star = (ImageView) itemView.findViewById(R.id.CHAT_ITEM_star);
Fonts.setTypeface(tvName, regular);
}
#Override
public void onClick(View view) {
int position = getLayoutPosition();
select(position);
}
}
Unfortunately it's very important for me to able to access the position of the clicked item in the whole dataset, in order to remove it, so doing something like indexOfChild isn't acceptable too: I tried, but this method gives you the position of the item in the visibile part of the list, thus making list.remove(position) impossible.

Looking at the updated code: you are not setting the onClickListener to any of the views in the ViewHolder. It is an understandable mistake to forget the click listener.
Just use:
tvName.setOnClickListener(this);
star.setOnClickListener(this);
You can set to both or just one of them. You can also simply get the parent layout of these two views, so that the whole item itself in the adapter can be clickable.
itemView.setOnClickListener(this);

You can do it in your onBindViewHolder
#Override
public void onBindViewHolder(ReportViewHolder holder, int position {
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
// handle your click here.
} });
}

Simplely Click Handler your ViewHolder. Recycler View don't have special attaching click handlers like ListView which has the method setOnItemClickListener().
** public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener
** in public ViewHolder(Context context, View itemView) set public void onClick(View view)
** get position by: int position = getLayoutPosition(); User user = users.get(position);

How to perform programmatic click on a item in a RecyclerView?

Hi I have a app that uses a Recycler view to display a bunch of items. Now I want to run an android test on the list but I don't know how to set a programmatic click on a given item. Can anyone tell me how to achieve this?

You have to implement it from scratch. The RecyclerView lacks for some of the awesome features that a ListView provides by default. Given this, in the adapter you have to declare an interface for the Observer between Fragment/Activity and the RecyclerView.
The correct method to attach this click event is onBindViewHolder. Then in the adapter you keep the reference to the CustomListener or the View.OnClickListener.
Here is a quick example on how to do this:
#Override
public void onBindViewHolder(SearchListAdapter.ViewHolder holder, final int position) {
//Item clicked
holder.mParent.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Select or deselect
mListener.notify(holder, position);
}
});
}
And the ViewHolder should be like:
public class ViewHolder extends RecyclerView.ViewHolder {
private View mParent;
public ViewHolder(View itemView) {
super(itemView);
mParent = itemView;
}
}
Where mParent is the current row View.