ArrayList<Object> 中的类型不兼容错误

Question

我正在尝试将广告放在当前正在解析 JSON 文件的 RecyclerView 中，问题是当我尝试用广告或 JSON 中的数据填充 ArrayList 时，它会引发转换错误。

错误发生在两个地方，一个在RecyclerViewAdapter() 方法体中，另一个在BindViewHolder()。

这是我来自 RecyclerViewAdapter.java 的代码（错误在第 5 行注释）

private ArrayList<Object> arrayList = new ArrayList<>();

public RecyclerViewAdapter(Context context, ArrayList<CardSetterGetter> arrayList, ArrayList<String> favouriteItemList, int totalCount) {
    this.context = context;
    this.arrayList = arrayList; //Incompatible types.  Required: ArrayList<java.lang.object>;    found: ArrayList<com.comp.app.modal.CardSetterGetter>
    this.favouriteItemList = favouriteItemList;
    this.totalCount = totalCount;

}

onBindViewHolder()（第 27 行注释错误）

@Override
public void onBindViewHolder(final RecyclerViewHolder holder, final int position) {

    int viewType = getItemViewType(position);

    switch (viewType){

        case AD_VIEW_TYPE:
            NativeExpressAdViewHolder nativeExpressHolder = (NativeExpressAdViewHolder)holder;
            NativeExpressAdView adView = (NativeExpressAdView)arrayList.get(position);

            ViewGroup adCardView = (ViewGroup)nativeExpressHolder.itemView;
            adCardView.removeAllViews();

            if(adView.getParent() != null){
                ((ViewGroup)adView.getParent()).removeView(adView);
            }

            adCardView.addView(adView);
            break;

        case MENU_ITEM_VIEW_TYPE:

        default:
            String card_image;
            CardSetterGetter cardSetterGetter;
            cardSetterGetter = arrayList.get(position); //Incompatible types.  Required: ArrayList<com.comp.app.modal.CardSetterGetter>;    found: ArrayList<java.lang.object>;

            card_image = constants.SERVERIP.concat(cardSetterGetter.getImageurl());
            holder.cardSetterGetter = cardSetterGetter;
            holder.title.setText(cardSetterGetter.getImagetitle()); //set title

            PointF focusPoint = new PointF(0.5f, 0f);
            // your app populates the focus point

            holder.image // set image
                    .getHierarchy()
                    .setActualImageFocusPoint(focusPoint);
            holder.image.setImageURI(Uri.parse(card_image));
    }

}

这是我的 CardSetterGetter.java

public class CardSetterGetter implements Serializable {
    private  String  imagetitle ;
    private  String  imageurl;
    private  String  description;
    private  String  tag;
    private  boolean isFavorite;

    public String getImageId() {
        return imageId;
    }

    public void setImageId(String imageId) {
        this.imageId = imageId;
    }

    public String getFavourite() {
        return favourite;
    }

    public void setFavourite(String favourite) {
        this.favourite = favourite;
    }

    private  String  imageId ;
    private  String favourite ;



    public String getCategory() {
        return category;
    }

    public void setCategory(String category) {
        this.category = category;
    }

    public  String category;

    public CardSetterGetter(){

    }

    public String getImagetitle() {
        return imagetitle;
    }

    public void setImagetitle(String imagetitle) {
        this.imagetitle = imagetitle;
    }

    public String getImageurl() {
        return imageurl;
    }

    public void setImageurl(String imageurl) {
        this.imageurl = imageurl;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getTag() {
        return tag;
    }

    public void setTag(String tag) {
        this.tag = tag;
    }

    public CardSetterGetter(String imageurl , String imagetitle , String description , String category , String tag,String imageId ,String favourite){
        this.imageurl = imageurl ;
        this.imagetitle = imagetitle ;
        this.description = description ;
        this.tag = tag ;
        this.category = category ;
        this.isFavorite =false ;
        this.imageId = imageId ;
        this.favourite = favourite ;
    }


    public boolean isFavorite() {
        return isFavorite;
    }

    public void setFavorite(String favorite) {
        favourite = favorite;
    }
}

我在 StackOverFlow 上尝试了一些类似这个 (Question) 的问题，但我无法理解解决方案的基本概念，我已经将数据类型更改为 Object（来自 CardSetterGetter）。

还告诉我，如果这个转换问题得到解决并且 arrayList 返回 adView 预期 CardSetterGetter 或反之亦然，我是否需要将所有此类语句放在 try catch 块中？

Answer 1

问题：您的 List 包含两种项目 CardSetterGetter 和 NativeExpressAdView 因此您需要使用 Objects 的 List 而不是任何特定类型，因为这两种类型没有关系并在适当的位置应用强制转换

使用这个

public RecyclerViewAdapter(Context context, ArrayList<Object> arrayList, ArrayList<String> favouriteItemList, int totalCount) {

并使用强制转换

cardSetterGetter =(CardSetterGetter ) arrayList.get(position); 

而不是

public RecyclerViewAdapter(Context context, ArrayList<CardSetterGetter> arrayList, ArrayList<String> favouriteItemList, int totalCount) {

还告诉我，如果这个铸造问题得到解决并且 arrayList 返回预期 CardSetterGetter 的 adView 或 反之亦然，我是否需要将所有此类语句放在 try catch 块中？

getItemViewType(position) 正在按照position 工作

   // ITEMS_PER_AD = 8
   return (position % MainActivity.ITEMS_PER_AD == 0) ? NATIVE_EXPRESS_AD_VIEW_TYPE
                : MENU_ITEM_VIEW_TYPE;

列表中 position % 8 == 0 项目 (0,8,16,24,32...) 的平均结果将是 NATIVE_EXPRESS_AD_VIEW_TYPE 类型，因此它是 position 依赖数学。

Answer 2

问题出在您的成员定义中：

private ArrayList<Object> arrayList = new ArrayList<>();

应该是这样的：

private ArrayList<CardSetterGetter> arrayList = new ArrayList<>();

这里的问题是ArrayList<CardSetterGetter> 不能分配给ArrayList<Object> - 尽管CardSetterGetter（和所有对象）都可以分配给Object。

Answer 3

像这样改变arraylist初始化

private ArrayList<CardSetterGetter> arrayList = new ArrayList<>();

Answer 4

在 RecyclerViewAdapter.java 中更改 ArrayList<Object> arrayList

private ArrayList<Object> arrayList = new ArrayList<>();

到

private ArrayList<CardSetterGetter> arrayList = new ArrayList<>();

这会解决你的问题