recyclerview获取错误的动画

Question

我想为recyclerview使用动画，但当为recyclerview使用动画时，强制关闭我的应用程序并显示上下文错误即使我不能在适配器中使用toast如何在适配器中使用动画并解决上下文问题，我放了我的代码，如何能解决我的问题或适配器？请帮助我

public class adapter_zakeran_any extends
    RecyclerView.Adapter<adapter_zakeran_any.ItemViewHolder> {

private Context contex;
private ArrayList<Item_zakerin_any> itemlist;
Item_zakerin_any item;
int pos;
String nameeee;
int DownloadComplete;
//  String file;
public Product product;
String mylink, myname, mynamelist, namemadahi_h, namemadah_h;
public SqliteDatabase mDatabase;
private long Music_DownloadId;
private DownloadManager downloadManager;
String namee;
String file;
View view;


//  private EditText linkFileEdt;
private Intent playerService;
public static TextView namemadahi, onvanmadahi;


public static ImageView download, albumart;

String speaker_name, masir, link, imagee;
MediaMetadataRetriever metaRetriver;
byte[] art;
String flink, shname, shonvane;
SharedPreferences preferences;


int lastPosition = -1;


public adapter_zakeran_any(Context contex, ArrayList<Item_zakerin_any> itemlist) {
    this.contex = contex;
    this.itemlist = itemlist;
}

@Override
public adapter_zakeran_any.ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

    LayoutInflater inflater = LayoutInflater.from(parent.getContext());
    view = inflater.from(parent.getContext())
            .inflate(R.layout.cardview_zakeran_any, parent, false);
    adapter_zakeran_any.ItemViewHolder itemViewHolder = new adapter_zakeran_any.ItemViewHolder(view);
    return itemViewHolder;
}

@Override
public void onBindViewHolder(adapter_zakeran_any.ItemViewHolder holder, int position) {

    item = itemlist.get(position);
    nameeee = item.getInfo();


    holder.namemadahi.setText(item.getInfo());
    holder.madah.setText(item.getSpeaker_name());
    holder.link.setText(item.getFile());
    final String ml = (String) holder.link.getText();


    namemadahi_h = (String) holder.namemadahi.getText();
    namemadah_h = item.getSpeaker_name();


    Animation animation = AnimationUtils.loadAnimation(contex, R.anim.item_animation_fall_down);
    holder.itemView.startAnimation(animation);
    lastPosition = position;


}

@Override
public int getItemCount() {
    if (itemlist != null) {
        return itemlist.size();

    }

    return 0;
}


public static class ItemViewHolder extends RecyclerView.ViewHolder {


    public CardView cvItem;
    public TextView namemadahi;
    public TextView madah;
    public TextView link;
    public ImageView download_any_rv;


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

        cvItem = (CardView) itemView.findViewById(R.id.cardView);
        namemadahi = (TextView) itemView.findViewById(R.id.namemadahi);
        madah = (TextView) itemView.findViewById(R.id.madah);


        link = (TextView) itemView.findViewById(R.id.link);
        download_any_rv = (ImageView) itemView.findViewById(R.id.download_anyrv);


    }
}

我的错误

Answer 1

您会得到错误，因为当最后一个项目出现时，它会得到null值。

Android.View.Animation.AnimationUtils.LoadAnimation处的java.lang.NullPointerException（AnimationUtils.java:71)

试试看：在适配器类上创建一个方法，并从OnBindViewWholder方法调用

setAnimation(holder.itemView, position);

全局初始化

 // Allows to remember the last item shown on screen
    private int lastPosition = -1; 

以下是完整代码：

        @Override
    public void onBindViewHolder(adapter_zakeran_any.ItemViewHolder holder, int position) {

        item = itemlist.get(position);
        nameeee = item.getInfo();


        holder.namemadahi.setText(item.getInfo());
        holder.madah.setText(item.getSpeaker_name());
        holder.link.setText(item.getFile());
        final String ml = (String) holder.link.getText();


        namemadahi_h = (String) holder.namemadahi.getText();
        namemadah_h = item.getSpeaker_name();

     // Here you apply the animation when the view is bound
        setAnimation(holder.itemView, position);

    }

 /**
     * Here is the key method to apply the animation
     */
    private void setAnimation(View viewToAnimate, int position)
    {
        // If the bound view wasn't previously displayed on screen, it's animated
        if (position > lastPosition)
        {
            Animation animation = AnimationUtils.loadAnimation(context, R.anim.item_animation_fall_down);
            viewToAnimate.startAnimation(animation);
            lastPosition = position;
        }
    }