I make a drop-down list, here's the code. I assume that the error is related to LayoutInflater but I cannot figure out how to do it correctly.
public class CompRVAdapter extends RecyclerView.Adapter<CompRVAdapter.ViewHolder> { CardView cardView; @NonNull @Override public CompRVAdapter.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) { View view = LayoutInflater.from(parent.getContext()) .inflate(R.layout.fragment_comp, parent, false); View child_view = LayoutInflater.from(parent.getContext()) .inflate(R.layout.fragment_child_1, parent, true); return new ViewHolder(view, child_view); } @Override public void onBindViewHolder(@NonNull CompRVAdapter.ViewHolder holder, int position) { } @Override public int getItemCount() { return 15; } public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener { public ViewHolder(View itemView, View childView) { super(itemView); cardView = (CardView) itemView.findViewById(R.id.cv1); CardView childCardView = (CardView) childView.findViewById(R.id.child_cv); LinearLayout linearLayout_childItems = (LinearLayout) itemView.findViewById(R.id.child_linear_layout); for (int indexView = 0; indexView < 3; indexView++) { LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT); linearLayout_childItems.addView(childCardView, layoutParams); } } @Override public void onClick(View view) { } } } Here is the text of the error
java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first. at android.view.ViewGroup.addViewInner(ViewGroup.java:4417) at android.view.ViewGroup.addView(ViewGroup.java:4258) at android.view.ViewGroup.addView(ViewGroup.java:4230) at ru.human_factors.characterist.adapters.CompRVAdapter$ViewHolder.<init>(CompRVAdapter.java:44) at ru.human_factors.characterist.adapters.CompRVAdapter.onCreateViewHolder(CompRVAdapter.java:22) at ru.human_factors.characterist.adapters.CompRVAdapter.onCreateViewHolder(CompRVAdapter.java:13) at android.support.v7.widget.RecyclerView$Adapter.createViewHolder(RecyclerView.java:6685) at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5869) at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5752) at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5748) at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2232) at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1559) at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1519) at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:614) at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3812) at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3529) at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:4082) at android.view.View.layout(View.java:17637) at android.view.ViewGroup.layout(ViewGroup.java:5575) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) at android.widget.FrameLayout.onLayout(FrameLayout.java:261) at android.view.View.layout(View.java:17637) at android.view.ViewGroup.layout(ViewGroup.java:5575) at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741) at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585) at android.widget.LinearLayout.onLayout(LinearLayout.java:1494) at android.view.View.layout(View.java:17637) at android.view.ViewGroup.layout(ViewGroup.java:5575) at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1079) at android.view.View.layout(View.java:17637) at android.view.ViewGroup.layout(ViewGroup.java:5575) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) at android.widget.FrameLayout.onLayout(FrameLayout.java:261) at android.view.View.layout(View.java:17637) at android.view.ViewGroup.layout(ViewGroup.java:5575) at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:443) at android.view.View.layout(View.java:17637) at android.view.ViewGroup.layout(ViewGroup.java:5575) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) at android.widget.FrameLayout.onLayout(FrameLayout.java:261) at android.view.View.layout(View.java:17637) at android.view.ViewGroup.layout(ViewGroup.java:5575) at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741) at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585) at android.widget.LinearLayout.onLayout(LinearLayout.java:1494) at android.view.View.layout(View.java:17637) at android.view.ViewGroup.layout(ViewGroup.java:5575) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) at android.widget.FrameLayout.onLayout(FrameLayout.java:261) at com.android.internal.policy.DecorView.onLayout(DecorView.java:726) at android.view.View.layout(View.java:17637) at android.view.ViewGroup.layout(ViewGroup.java:5575) at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2346) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2068) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1254) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6337) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:874) at android.view.Choreographer.doCallbacks(Choreographer.java:686) at android.view.Choreographer.doFrame(Choreographer.java:621) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:860) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6119) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
