From RecyclerView
item, I am trying to save the selected RadioButton's text in model class. When I select a RadioButton
from 1st item, it's text is saved appropriately. Problem is, RadioButton's text at the same position from 8th item is also auto saved. If I select radio button from 2nd item, text from 9th item is also auto saved, and so on. How to solve this problem?
onBindViewHolder method is given below :
@Override
public void onBindViewHolder(@NonNull final ViewHolder holder, final int position) {
...
holder.radioGroup.setTag(position);
holder.radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(RadioGroup group, int checkedId) {
int radioButtonID = group.getCheckedRadioButtonId();
RadioButton radioButton = (RadioButton) group.findViewById(radioButtonID);
int clickedPos = (Integer) group.getTag();
models.get(clickedPos).setChecked(radioButtonID);
if (radioButtonID > 0){
models.get(clickedPos).setSelectedAns(radioButton.getText().toString());
}
}
});
holder.radioGroup.check(models.get(position).getChecked());
Log.d("TAG", "At position " + position + " selected : " + models.get(position).getSelectedAns());
}
The problem is that although the code looks correct on the surface, what's actually happening is that when you call holder.radioGroup.check()
, it triggers your onCheckedChanged()
event handler just the same as if the user had initiated it.
Since the views are recycled, the view at position 0 is being reused for position 8 in the list. So the call to check()
in onBindViewHolder()
will call onCheckedChanged()
, with the checked radio button from position 0 still checked (ie checkedId
and radioGroup. getCheckedRadioButtonId()
will return the ID of the radiobutton checked when the view was used at position 0).
The real crux is this
models.get(clickedPos).setChecked(radioButtonID);
Consider the first paragraphs of the answer, and you'll realize that this will (incorrectly) update the model item at position 8 with the radioButtonID
that was checked when this view was used at position 0.
One way to solve this is to distinguish between a user-initiated change and a binding-initiated change. You can for example do this by adding a field to the ViewHolder
to indicate if the view is currently binding.
class ViewHolder extends RecyclerView.ViewHolder{
TextView selectedAnswer;
RadioGroup radioGroup;
boolean isBinding;
ViewHolder(View itemView) {
super(itemView);
radioGroup = itemView.findViewById(R.id.radioGroup);
radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(RadioGroup group, int checkedId) {
int position = getAdapterPosition();
RadioButton radioButton = (RadioButton) group.findViewById(checkedId);
/* Only update the model when onCheckedChange() was initiated by the user clicking
a radio button, not when the adapter is binding the view. In that scenario, we
are only interested in passing information FROM the model TO the view. */
if( !isBinding ) {
models.get(position).setChecked(checkedId);
models.get(position).setSelectedAns(radioButton != null ? radioButton.getText().toString() : "");
}
selectedAnswer.setText( models.get(position).getSelectedAns() );
}
});
...
}
}
@Override
public void onBindViewHolder(@NonNull final ViewHolder holder, final int position) {
holder.isBinding = true;
...
/* When calling check() here, we invoke onCheckedChanged(), which will
update the textview that displays the selected answer - so no need to call
holder.selectedAnswer.setText( models.get(position).getSelectedAns() )
from here */
holder.radioGroup.check(models.get(position).getChecked());
holder.isBinding = false;
}
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