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How to make the holder in if else statements of onClick method work without final in argument Viewholder in arguments of onBindViewHolder method

I am trying to make a text change when a button located along with the text (layoutPasswd) in recycler view and to change it back if the button is again pressed.Like a password hiding button. The values to the adapter is from a static class object as arraylist. The problem occurring now is that the value for all the items (only for layoutPasswd) in recycler view is same.
public void onBindViewHolder(#NonNull final viewHolder holder, int position) {
holder.layoutUName.setText(users.get(position).getUserName());
pos = position;
holder.layoutPasswd.setText("********");
holder.btnViewChanger.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (holder.view1) {
holder.layoutPasswd.setText(users.get(pos).getPasswd());
holder.btnViewChanger.setText("hide");
holder.view1 = false;
} else {
holder.layoutPasswd.setText("********");;
holder.btnViewChanger.setText("Show");
holder.view1 = true;
}
}
});

You cannot rely on the ViewHolders or Views in a RecyclerView to hold any state, because they are recycled. Every time a view scrolls onto the screen, first it calls your onBindViewHolder function to update the contents of that ViewHolder to match the data.
Any configuration you set on the views or the ViewHolder instance in onBindViewHolder cannot be relied on to stay the same if the view scrolls off the screen, because the original ViewHolder might be recycled to be used for some other data, and when it scrolls back on screen, you might be looking at some other view that has been recycled from other data that just scrolled off the screen.
So if your views have configuration that you want to "stick", you have to back it up when you change it, and restore it in onBindViewHolder. The way you accomplish this will depend on how you are managing the data that you pass to the adapter.
If you can modify your User class, you can add a Boolean to it that stores whether it should show the password. Then in your onBindViewHolder, you restore the state based on this Boolean. And you also update this Boolean when the state changes.
I also updated the way the click listener works to simplify it for toggling. I removed the pos = position line, because almost certainly that is not something you should be doing.
public void onBindViewHolder(#NonNull final viewHolder holder, int position) {
final User user = users.get(position)
holder.layoutUName.setText(user.getUserName());
holder.layoutPasswd.setText(user.isShowPassword() ? user.getPasswd() : "********");
holder.btnViewChanger.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
user.setShowPassword(!user.isShowPassword());
holder.layoutPasswd.setText(user.isShowPassword() ? user.getPasswd() : "********");
holder.btnViewChanger.setText(user.isShowPassword() ? "hide" : "show");
}
});
// ...
}
If you cannot modify the User class, this is more complicated. Then the adapter should have its own ArrayList<Boolean> to store the state by position index, but you need to keep this list at least as long as the data that is bound, and reset everything to false if the whole list of data is refreshed.

Get clicked Image properties

Imagine a gallery application (sort of).
But instead of gallery I want to present a choice in form of 10 images displayed onto the screen.
How should you detect the one that user has clicked on?
What is a best way to implement this? Should I use ImageView and onClick method?
Imagine implementing onClick event for a 100 ImageViews?
?for every ImageView displayed onto the screen check if it contains user touch coordinates?
Same question bothers me for how to detect if the user has touched a Bitmap drawn onto a canvas.
Java, Android.

You're going to want to use a RecyclerView with an ImageView in your list item's layout xml.
You can create a clickable ViewHolder like this:
class ClickableViewHolder(final override val containerView: View, onClick: (position: Int) -> Unit) : RecyclerView.ViewHolder(containerView) {
init {
containerView.setOnClickListener {
val pos = absoluteAdapterPosition
// check if item still exists
if (pos != RecyclerView.NO_POSITION) {
onClick(pos)
}
}
}
}
Usage in your Adapter class:
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val v = LayoutInflater.from(parent.context).inflate(R.layout.list_item, parent, false)
return ClickableViewHolder(v) { position: Int ->
getItem(position)?.let {
//Do something here
}
}
}

How to change single item in recycler view without screen reload?

I have Recycler View with a lot of items in. What I want to do is to change the text in TextView inside item that was clicked. I did it in that way:
wordList.set(position, newWord);
MyProgressActivityAdapter newAdapter = new MyProgressActivityAdapter(wordList, this);
newAdapter.notifyItemChanged(position);
recyclerView.setAdapter(newAdapter);
And everything works fine except of the fact that the screen goes to the top every time I click item. What can I do to avoid that?

You should use the payload version of notifyItemChanged, here is a simple example for you to get the hang of it:
adapter.notifyItemChanged(position, "updateText");
And then in your RecyclerAdapter override the payload version of onBindViewHolder:
#Override
public void onBindViewHolder(#NonNull RecyclerView.ViewHolder holder, int position, #NonNull List payloads) {
if (payloads.isEmpty()) onBindViewHolder(holder, position);
else if ("updateText".equals(payloads.get(0))) {
if (holder instanceof YourViewHolder) {
((YourViewHolder) holder).textView.setText(dataProvider.get(position).getNewText());
}
}
}
Note that this approach prevents RecyclerView from creating a new ViewHolder and then binding your data, so you should just call the notifyItemChanged without resetting the adapter and so.

notifyItemChanged(position) should work if you handle it correctly. Try to handle this inside onBindViewHolder like below:
override fun onBindViewHolder(holder: RecyclerHolder, position: Int) {
holder.itemView.text_view.text = items[position]
holder.itemView.button.setOnClickListener {
items[position] = "New Text"
notifyItemChanged(position)
}
}

I can't display both Persian and English texts together in RecyclerView

I have a RecylcerView which loads it's data from an external server. And each of my items have a TextView. My problem is that some of my items don't have their related values for TextView when both English and Persian texts are used, and it shows nothing in the TextView. But it perfectly works fine when just one language, either English or Persian is used. By one language I mean all of the data in adapter be in one language not just one item.
Besides, my adapter gets it's data from external server, so I can't store my texts in /res folder. In addition, getText() in my code always shows the correct value.
#Override
public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int i) {
if(viewHolder instanceof ItemViewHolder) {
final CategoryItem nature = mItems.get(i);
String itemName = mItems.get(i).getName();
//This line of code doesn't work for some items when both English and Arabic texts are used
((ItemViewHolder) viewHolder).dsc.setText(itemName);
//This line of code shows the correct values at all times
System.out.println("itemName " + ((ItemViewHolder) viewHolder).dsc.getText());
}else{
((ProgressViewHolder)viewHolder).progressBar.setIndeterminate(true);
}
}
As shown in the picture, there are some items which have empty TextView. The three values for empty items of this picture should be: bb, سلام , bbسلام

A short example of multiple viewholders.
May be after this your code will be clearer
public class yourAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
class ItemViewHolder extends RecyclerView.ViewHolder {
...
}
class ProgressViewHolder extends RecyclerView.ViewHolder {
...
}
#Override
public int getItemViewType(int position) {
//here is the place where viewholder may choose
return position;
}
#Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
switch (viewType) {
case 0: return new ItemViewHolder(...);
case 1: return new ProgressViewHolder(...);
...
}
}
}

After researching I figured out that my TextViews become visible after pressing Request Layout button in Hierarchy Viewer tool in Android Studio. So, I added one line to my code after setText()
((ItemViewHolder) viewHolder).dsc.requestLayout();
And after that, everything worked fine.
I would be really thankful If anyone could explain the reason.

ViewPager and AsyncTask for loading the Items

I've a ViewPager with an PageAdapter loading ImageViews.
The images displayed come from the internet and I use an AsyncTask for loading the Bitmap and then (if the Page hasn't been destroyed) assign it to the ImageView.
#Override
public Object instantiateItem(ViewGroup container, int position) {
ImageView img = new ImageView(container.getContext());
new LoadImageTask(img,Data.getImageUrL(position)).execute();
container.addView(img );
return img;
}
So the ImageView has two states: loading or loaded. I need to track if the user waits for the image. So I implement this at the LoadImageTask onPostExecute:
if (loadListener != null) {
loadListener.onImageLoaded(position);
}
And in the listener:
public void onImageLoaded(int position) {
if (position == mViewPager.getCurrentItem()) {
// Save record ..
}
}
Since I only need to count the images displayed at the "Current Item of the ViewPager" this method is not enought because if the user moves to the item 5 for example, the ViewPager loads in cache the item 6. If the user waits enought time for this load (beeing the item 5 the current) the callback to onImageLoaded is lost (because the item 6 is not the currentItem at the moment, and then when the user moves to the item 6 I've no way of knowing if the image is loaded or not.
I was thinking in adding something like [[PSEUDOCODE]]:
mViewPager.setOnPageChangeListener(new OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
if (mViewPager.isLoaded(posistion)){
// Save record ...
}
}
But I dont know how to retrieve if the corresponding view loaded the image or not at this moment. How can I do it?