onCreateViewHolder only creates a new view holder when there are no existing view holders which the RecyclerView can reuse. So, for instance, if your RecyclerView can display 5 items at a time, it will create 5-6 ViewHolders , and then automatically reuse them, each time calling onBindViewHolder .
A ViewHolder describes an item view and metadata about its place within the RecyclerView. RecyclerView. Adapter implementations should subclass ViewHolder and add fields for caching potentially expensive View. findViewById(int) results.
Based on the link: Why doesn't RecyclerView have onItemClickListener()? and How RecyclerView is different from Listview?, and also @Duncan's general idea, I give my solution here:
Define one interface RecyclerViewClickListener
for a passing message from the adapter to Activity
/Fragment
:
public interface RecyclerViewClickListener {
public void recyclerViewListClicked(View v, int position);
}
In Activity
/Fragment
implement the interface, and also pass listener to adapter:
@Override
public void recyclerViewListClicked(View v, int position){... ...}
//set up adapter and pass clicked listener this
myAdapter = new MyRecyclerViewAdapter(context, this);
In Adapter
and ViewHolder
:
public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyRecyclerViewAdapter.ItemViewHolder> {
... ...
private Context context;
private static RecyclerViewClickListener itemListener;
public MyRecyclerViewAdapter(Context context, RecyclerViewClickListener itemListener) {
this.context = context;
this.itemListener = itemListener;
... ...
}
//ViewHolder class implement OnClickListener,
//set clicklistener to itemView and,
//send message back to Activity/Fragment
public static class ItemViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
... ...
public ItemViewHolder(View convertView) {
super(convertView);
... ...
convertView.setOnClickListener(this);
}
@Override
public void onClick(View v) {
itemListener.recyclerViewListClicked(v, this.getPosition());
}
}
}
After testing, it works fine.
[UPDATE]
Since API 22, RecyclerView.ViewHolder.getPosition()
is deprecated, so instead with getLayoutPosition()
.
public class MyRvAdapter extends RecyclerView.Adapter<MyRvAdapter.MyViewHolder>{
public Context context;
public ArrayList<RvDataItem> dataItems;
...
constructor
overrides
...
class MyViewHolder extends RecyclerView.ViewHolder{
public TextView textView;
public Context context;
public MyViewHolder(View itemView, Context context) {
super(itemView);
this.context = context;
this.textView = (TextView)itemView.findViewById(R.id.textView);
// on item click
itemView.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
// get position
int pos = getAdapterPosition();
// check if item still exists
if(pos != RecyclerView.NO_POSITION){
RvDataItem clickedDataItem = dataItems.get(pos);
Toast.makeText(v.getContext(), "You clicked " + clickedDataItem.getName(), Toast.LENGTH_SHORT).show();
}
}
});
}
}
}
Here is an Example to set a Click Listener.
Adapter extends RecyclerView.Adapter<MessageAdapter.MessageViewHolder> { ... }
public static class MessageViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public TextView tv_msg;
public TextView tv_date;
public TextView tv_sendTime;
public ImageView sharedFile;
public ProgressBar sendingProgressBar;
public MessageViewHolder(View v) {
super(v);
tv_msg = (TextView) v.findViewById(R.id.tv_msg);
tv_date = (TextView) v.findViewById(R.id.tv_date);
tv_sendTime = (TextView) v.findViewById(R.id.tv_sendTime);
sendingProgressBar = (ProgressBar) v.findViewById(R.id.sendingProgressBar);
sharedFile = (ImageView) v.findViewById(R.id.sharedFile);
sharedFile.setOnClickListener(this);
}
@Override
public void onClick(View view) {
int position = getAdapterPosition();
switch (view.getId()){
case R.id.sharedFile:
Log.w("", "Selected"+position);
break;
}
}
}
Put this code where you define recycler view in activity.
rv_list.addOnItemTouchListener(
new RecyclerItemClickListener(activity, new RecyclerItemClickListener.OnItemClickListener() {
@Override
public void onItemClick(View v, int position) {
Toast.makeText(activity, "" + position, Toast.LENGTH_SHORT).show();
}
})
);
Then make separate class and put this code:
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
public class RecyclerItemClickListener implements RecyclerView.OnItemTouchListener {
private OnItemClickListener mListener;
public interface OnItemClickListener {
public void onItemClick(View view, int position);
}
GestureDetector mGestureDetector;
public RecyclerItemClickListener(Context context, OnItemClickListener listener) {
mListener = listener;
mGestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
@Override
public boolean onSingleTapUp(MotionEvent e) {
return true;
}
});
}
@Override
public boolean onInterceptTouchEvent(RecyclerView view, MotionEvent e) {
View childView = view.findChildViewUnder(e.getX(), e.getY());
if (childView != null && mListener != null && mGestureDetector.onTouchEvent(e)) {
mListener.onItemClick(childView, view.getChildAdapterPosition(childView));
}
return false;
}
@Override
public void onTouchEvent(RecyclerView view, MotionEvent motionEvent) {
}
@Override
public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
}
}
create java file with below code
public class RecyclerItemClickListener implements RecyclerView.OnItemTouchListener {
private OnItemClickListener mListener;
public interface OnItemClickListener {
public void onItemClick(View view, int position);
}
GestureDetector mGestureDetector;
public RecyclerItemClickListener(Context context, OnItemClickListener listener) {
mListener = listener;
mGestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
@Override public boolean onSingleTapUp(MotionEvent e) {
return true;
}
});
}
@Override public boolean onInterceptTouchEvent(RecyclerView view, MotionEvent e) {
View childView = view.findChildViewUnder(e.getX(), e.getY());
if (childView != null && mListener != null && mGestureDetector.onTouchEvent(e)) {
mListener.onItemClick(childView, view.getChildLayoutPosition(childView));
return true;
}
return false;
}
@Override public void onTouchEvent(RecyclerView view, MotionEvent motionEvent) { }
@Override
public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
}
and just use the listener on your RecyclerView object.
recyclerView.addOnItemTouchListener(
new RecyclerItemClickListener(context, new RecyclerItemClickListener.OnItemClickListener() {
@Override public void onItemClick(View view, int position) {
// TODO Handle item click
}
}));
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