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Android ViewHolder parameter from RecyclerView # onCreateViewHolder differents

This is an example of the code that I followed.

And the code below is part of the onCreateViewHolder in the sample code:

 @Override public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { // create a new view View v = LayoutInflater.from(parent.getContext()) .inflate(R.layout.my_text_view, parent, false); // set the view size, margins, paddings and layout parameters ... ViewHolder vh = new ViewHolder(v); return vh; }

And this is part of ViewHolder:

 public static class ViewHolder extends RecyclerView.ViewHolder { public TextView mTextView; public ViewHolder(TextView v) { super(v); mTextView = v; } }

Obviously, the TextView v parameter is incorrect.

Then I play the trick in the onCreateViewHolder method as follows:

  ... TextView textView = (TextView) v.findViewById(R.id.tv_test); ViewHolder vh = new ViewHolder(textView);

But when I started the application, I got an exception.

  java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child parent first. at android.view.ViewGroup.addViewInner(ViewGroup.java:3693) at android.view.ViewGroup.addView(ViewGroup.java:3546) at android.view.ViewGroup.addView(ViewGroup.java:3491) at android.support.v7.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:3533) at android.support.v7.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:3558) at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1012) at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:524) at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:1461) at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:1600) at android.view.View.layout(View.java:15273) at android.view.ViewGroup.layout(ViewGroup.java:4763) at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1069) at android.view.View.layout(View.java:15273) at android.view.ViewGroup.layout(ViewGroup.java:4763) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:457) at android.widget.FrameLayout.onLayout(FrameLayout.java:392) at android.view.View.layout(View.java:15273) at android.view.ViewGroup.layout(ViewGroup.java:4763) at com.android.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:494) at android.view.View.layout(View.java:15273) at android.view.ViewGroup.layout(ViewGroup.java:4763) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:457) at android.widget.FrameLayout.onLayout(FrameLayout.java:392) at android.view.View.layout(View.java:15273) at android.view.ViewGroup.layout(ViewGroup.java:4763) at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2057) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1814) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1044) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5749) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767) at android.view.Choreographer.doCallbacks(Choreographer.java:580) at android.view.Choreographer.doFrame(Choreographer.java:550) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753) at android.os.Handler.handleCallback(Handler.java:738) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5070) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:836) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:631)

BUT, when I change the ViewHolder code as follows:

  public ViewHolder(View v) { super(v); mTextView = (TextView) v; }

Everything will be good.

I want to know what this exception means? What happened to this exception?

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1 answer

I stumbled on the same pattern and was soon puzzled. The view that is passed to the ViewHolder, so the constructor is a bloated parent view containing all of your views in one list item. Use this traversed view to initialize all ViewHolder fields in its constructor as follows:

 public class MyViewHolder extends RecyclerView.ViewHolder { public TextView titleWithIcon; public TextView teaser; public MyViewHolder(View itemView) { super(itemView); titleWithIcon = (TextView) itemView.findViewById(R.id.title_with_icon); teaser = (TextView) itemView.findViewById(R.id.teaser); } }
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Source: https://habr.com/ru/post/1201442/

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