單擊項目后，如何從RecyclerView適配器內部的drawable更改imageView的圖像？

Question

1. 我從SERVER提取了數據以填充RECYCLER視圖
2. 我在每個recyclerview行中都有一個imageview

3. 當我單擊該圖像視圖時，我想將可繪制對象加載到該圖像視圖中

    holder.imageView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { Drawable placeholder = holder.imageView.getContext().getResources().getDrawable(R.drawable.app); holder.imageView.setImageDrawable(placeholder); } }); 

上面是我嘗試過的內容，但是它說“ holder”需要聲明為final，但實際上，我什至沒有提到我可以寫“ finalholder”或其他方式。

我的ADAPTER代碼：

public class ProductsAdapter extends 
RecyclerView.Adapter<ProductsAdapter.ProductViewHolder> {


private Context mCtx;
private List<Product> productList;

public ProductsAdapter(Context mCtx, List<Product> productList) {
    this.mCtx = mCtx;
    this.productList = productList;
}

@Override
public ProductViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    LayoutInflater inflater = LayoutInflater.from(mCtx);
    View view = inflater.inflate(R.layout.product_list, null);
    return new ProductViewHolder(view);
}

@Override
public void onBindViewHolder(ProductViewHolder holder, int position) {
    final Product product = productList.get(position);

    //loading the image
    Glide.with(mCtx)
            .load(product.getImage())
            .into(holder.imageView);

    holder.textViewTitle.setText(product.getTitle());
    holder.textViewShortDesc.setText(product.getShortdesc());
    holder.textViewRating.setText(String.valueOf(product.getRating()));
    holder.textViewPrice.setText(String.valueOf(product.getPrice()));


    holder.imageView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {


            Drawable placeholder = holder.imageView.getContext().getResources().getDrawable(R.drawable.app);
            holder.imageView.setImageDrawable(placeholder);

        }
    });



        }

@Override
public int getItemCount() {
    return productList.size();
}

class ProductViewHolder extends RecyclerView.ViewHolder {

    TextView textViewTitle, textViewShortDesc, textViewRating, textViewPrice;
    ImageView imageView;

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

        textViewTitle = itemView.findViewById(R.id.textViewTitle);
        textViewShortDesc = itemView.findViewById(R.id.textViewShortDesc);
        textViewRating = itemView.findViewById(R.id.textViewRating);
        textViewPrice = itemView.findViewById(R.id.textViewPrice);
        imageView = itemView.findViewById(R.id.imageView);
    }
}
}

Answer 1

您可以在方法標頭中聲明Holder final

public void onBindViewHolder(final ProductViewHolder holder, int position) {
    Your code here
}

Answer 2

有幾種解決方案：

1）讓您的持有人做最后一件事

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

或使用其他變量

final Holder finalHolder = holder;
holder.imageView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {


            Drawable placeholder = finalHolder.imageView.getContext().getResources().getDrawable(R.drawable.app);
            holder.imageView.setImageDrawable(placeholder);

        }
    });

2）在特定視圖上設置ClickListener時，請確保只有該視圖會觸發操作，因此您可以使用該知識

holder.imageView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            ImageView imgView = (ImageView) view;
            Drawable placeholder = imgView.getContext().getResources().getDrawable(R.drawable.app);
            imgView.setImageDrawable(placeholder);

        }
    });