Setting the background image of a CardView inside RecyclerView causes the program to crash when scrolling

问题

I have a RecyclerView containing a list of CardViews with information that is pulled from a server, some cards have only a background color but some contains a background image. If the cards all have just background colors, the RecyclerView behaves accordingly (I am able to set the margins and corner radius as well). However, if any one card contains a background image, a crash will happen when I try to scroll up/down the list (although the background image will load without the previously set corner radius).

Here is the crash log:

java.lang.ClassCastException: android.graphics.drawable.BitmapDrawable cannot be cast to android.support.v7.widget.RoundRectDrawable
        at android.support.v7.widget.CardViewApi21.setBackgroundColor(CardViewApi21.java:107)
        at android.support.v7.widget.CardView.setCardBackgroundColor(CardView.java:234)
        at co.roverlabs.sdk.ui.CardListAdapter.onBindViewHolder(CardListAdapter.java:88)
        at co.roverlabs.sdk.ui.CardListAdapter.onBindViewHolder(CardListAdapter.java:28)
        at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:4402)
        at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:3717)
        at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:3609)
        at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1859)
        at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1311)
        at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1274)
        at android.support.v7.widget.LinearLayoutManager.scrollBy(LinearLayoutManager.java:1102)
        at android.support.v7.widget.LinearLayoutManager.scrollVerticallyBy(LinearLayoutManager.java:959)
        at android.support.v7.widget.RecyclerView$ViewFlinger.run(RecyclerView.java:3062)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
        at android.view.Choreographer.doCallbacks(Choreographer.java:580)
        at android.view.Choreographer.doFrame(Choreographer.java:549)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5254)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

Here is my onBindViewHolder() method (simplified with hard coded values for easier reading):

public void onBindViewHolder(final CardViewHolder holder, int position) {

    //Set margins
    CardView.LayoutParams cardLayoutParams = new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 2000);
    cardLayoutParams.setMargins(20, 20, 20, 20);
    holder.cardView.setLayoutParams(cardLayoutParams);

    //Set background color or image
    if(view.hasBackgroundImage()) {
        holder.cardView.setBackground(R.drawable.background);
    }
    else {
        holder.cardView.setCardBackgroundColor(Color.CYAN);
    }

    //Set border radius
    holder.cardView.setRadius(20);

    //Set elevation
    holder.cardView.setCardElevation(0);

Here is my onCreateViewHolder() method and custom Recycler.ViewHolder method:

public CardViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

    View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.card_view, parent, false);
    return new CardViewHolder(itemView);
}

public class CardViewHolder extends RecyclerView.ViewHolder {

    protected CardView cardView;

    public CardViewHolder(View view) {

        super(view);
        cardView = (CardView)view.findViewById(R.id.single_card_view);
    }
}

And finally, here is my XML file for the CardView:

<android.support.v7.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/single_card_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <RelativeLayout
        android:id="@+id/single_card_view_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    </RelativeLayout>

</android.support.v7.widget.CardView>

I just wish to know how to set the background of a CardView to a custom image instead of just a color, and if there are any workarounds. It is important for me to be able to set the corner radius of the cards. Thank you!

回答1:

Assuming you are using CardView, you cannot change background drawable because CardView uses background drawable to draw the card. You can change card background color via setCardBackgroundColor.

来源：https://stackoverflow.com/questions/29924560/setting-the-background-image-of-a-cardview-inside-recyclerview-causes-the-progra