java.lang.ClassCastException: android.widget.LinearLayout$LayoutParams cannot be cast to android.support.v7.widget.RecyclerView$LayoutParams

Question

I have a RecyclerView with a LinearLayout inside. The LinearLayout consists out of 9 buttons. Before some changes I could click the buttons and it didn't crashed. But after I added this code below it gives the error and does not show where it comes from:

java.lang.ClassCastException: android.widget.LinearLayout$LayoutParams cannot be cast to android.support.v7.widget.RecyclerView$LayoutParams

The imports in Adapter:

    import android.content.Context;
import android.graphics.Color;
import android.support.v7.widget.RecyclerView;
import android.widget.LinearLayout.LayoutParams;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;

Added this in the onClickListener:

tempTag = (int) v.getTag();
mAdapter.grayButton(tempTag / 9, tempTag % 9);
zahl1 = Integer.parseInt(mAdapter.getText(tempTag).toString());

Added this method in the RecyclerView.Adapter:

    public void grayButton(int row, int element){
    recycleViewDatas.get(row).setGray(element);
    notifyItemChanged(row);
}

Added this code in the onBindViewHolder:

LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
viewHolder.ll.setLayoutParams(lp);
lp.height = viewHolder.ll.getLayoutParams().height - (int) (viewHolder.buttons.get(j).getLayoutParams().height - recycleViewDatas.get(i).getSize()) + 30;
viewHolder.ll.setLayoutParams(lp);
if(recycleViewDatas.get(i).getGray() == j)
     viewHolder.buttons.get(j).setTextColor(Color.GRAY);
else if(recycleViewDatas.get(i).getGray() == -1)
     viewHolder.buttons.get(j).setTextColor(Color.BLACK);

This is my ViewHolder:

public static class ViewHolder extends RecyclerView.ViewHolder {
    LinearLayout ll;
    private ArrayList<Button> buttons = new ArrayList<>();

    public ViewHolder(View v, Context context) {
        super(v);

        ll = (LinearLayout) v.findViewById(R.id.llRecycleView);
        for (int i = 0; i < ll.getChildCount(); i++) {
            buttons.add((Button) ll.getChildAt(i));
        }
    }
}

The layout file of the recycleviewdata:

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:weightSum="9"
android:background="@drawable/zeile"
android:id="@+id/llRecycleView">

<Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:textColor="@android:color/black"
    android:background="@android:color/transparent"
    android:textSize="23sp"
    android:clickable="false"
    android:layout_gravity="center"
    android:gravity="center" />

...more buttons

The layout of the MainActivity:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">

<LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:weightSum="2"
    android:background="@drawable/top">
...some buttons
</LinearLayout>

<android.support.v7.widget.RecyclerView
    android:id="@+id/my_recycler_view"
    android:scrollbars="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/></LinearLayout>

I do not understand why the error comes after the update. And the app only crashes on my M9. On the HTC One V it does not crash and all works as expected. You know the problem? Do you need any more code?

Answer 1

Your problem is in onBindViewHolder:

LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);

LayoutParams is implemented for (almost) all the layouts. When you set LayoutParams on a view, you need to set it with a type of the view's parents. So if you have a LinearLayout and you are trying to add a Button, you need to set LinearLayout.LayoutParams on the Button. The problem in this case is that you don't know the parent type. And by that I mean it can different on different Android versions.

The safe bet is to use the LayoutParams from a common class (ViewGroup?) since you only set width and height.