ImageView.setBackgroundResource

Question

Attempt to invoke virtual method 'void android.widget.ImageView.setBackgroundResource(int)' on a null object reference at com.Adapter.MessageAdapter.onBindViewHolder(MessageAdapter.java:240) at com.Adapter.MessageAdapter.onBindViewHolder(MessageAdapter.java:37) at androidx.recyclerview.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:7093) at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:7172) at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:6037) at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6304) at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6143) at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6139) at androidx.recyclerview.widget.LinearLayoutManager$LayoutState.next

 public class ViewHolder extends RecyclerView.ViewHolder {

        public ImageView read_chat;

}

onBindViewHolder

public void onBindViewHolder(@NonNull MessageAdapter.ViewHolder holder, int position) {

    int type = holder.getItemViewType();
    Chat chat = mChat.get(position);

    if (chat.isIsseen()) {
        holder.read_chat. setBackgroundResource(R.drawable.ic_check_double_fill_read);    
    } else {
        holder.read_chat. setBackgroundResource(R.drawable.ic_check_double_fill);
    }

}

ViewHolder 视图

public ViewHolder(View itemView) {
super(itemView);

  read_chat = itemView.findViewById(R.id.read_chat);

}

Answer 1

我不确定你在 onCreateViewHolder 函数中做了什么，但通常当我看到这个时，是因为你夸大了错误的布局。确保你正在膨胀你的 list_item xml 布局。希望这有帮助。

Answer 2

试试这个

imageView.setImageDrawable(getResources().getDrawable(R.drawable.your_selected_image));