如何将上下文传递给毕加索

Question

你好，我正在尝试使用 Picasso 添加图像，但是当我使用以下视图持有者时，在适配器中获取 Picasso 的上下文时遇到问题：

这是我的适配器

               public class DataAdapter extends 
                  RecyclerView.Adapter<DataAdapter.ViewHolder> {
                            private ArrayList<String> 
                              al_prod_name,al_prod_price,al_prod_id,
                                 al_prod_image;

                    public DataAdapter(ArrayList<String> al_prod_id, 
                           ArrayList<String> al_prod_name,
                               ArrayList<String> al_prod_price, 
                                  ArrayList<String> al_prod_image) {
                                   this.al_prod_id = al_prod_id;
                                   this.al_prod_price = al_prod_price;
                                   this.al_prod_name = al_prod_name;
                                   this.al_prod_image = al_prod_image
                               }


                      public DataAdapter.ViewHolder 
                         onCreateViewHolder(ViewGroup viewGroup, int i) {
                              View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.cardrow, viewGroup, 
                                    false);
                              return new ViewHolder(view);
                             }

                        public void onBindViewHolder(DataAdapter.ViewHolder 
                          viewHolder, int i) {

                             viewHolder.tv_prod_name.setText
                               (al_prod_name.get(i));
                             viewHolder.tv_prod_price.setText
                               (al_prod_price.get(i));

                        Picasso.with().load(al_prod_image.get(i))
                       .placeholder(R.drawable.floatingicon)
                       .error(R.drawable.floatingicon).
                       .into(viewHolder.img_prod);

                          }
                      public int getItemCount() {
                      return al_prod_id.size();
                      }

                   public class ViewHolder extends RecyclerView.ViewHolder{
                      private TextView tv_prod_name,tv_prod_price;
                      private ImageView img_prod;
                      public ViewHolder(View view) {
                      super(view);

                       tv_prod_name = (TextView)view
                       .findViewById(R.id.tv_prod_name);
                        tv_prod_price = (TextView)view
                       .findViewById(R.id.tv_prod_price);
                       img_prod = (ImageView)view
                       .findViewById(R.id.img_prod);
                       }
                       }
                       }

请帮助获取 context.This 我是如何设置适配器的：

                       RecyclerView.Adapter adapter = new 
                       DataAdapter(al_prod_id,al_prod_name,
                       al_prod_price,al_prod_image);

Answer 1

在您的适配器 Context 上下文中声明一个数据成员；像这样为您的适配器编写构造函数，

DataAdapter(Context context, otherAurguments);

并且在创建适配器时

DataAdapter adapter = new DataAdapter(yourActivityName.this , otherAurguments);

Answer 2

将您的构造函数更改为

private Context context;
public DataAdapter(Context context, ArrayList<String> al_prod_id, 
                       ArrayList<String> al_prod_name,
                           ArrayList<String> al_prod_price, 
                              ArrayList<String> al_prod_image) {
                               this.context = context;
                               this.al_prod_id = al_prod_id;
                               this.al_prod_price = al_prod_price;
                               this.al_prod_name = al_prod_name;
                               this.al_prod_image = al_prod_image
                           }

现在将您的适配器命名为

RecyclerView.Adapter adapter = new 
                   DataAdapter(context, al_prod_id,al_prod_name,
                   al_prod_price,al_prod_image);

此处的上下文是您的 activity 参考。希望对你有帮助。

Answer 3

每个视图都有一个上下文。我建议您使用 getApplicationContext() 来防止应用程序在 activity 上下文变为 null

时崩溃

Picasso.with(itemView.getContext()).load(al_prod_image.get(i))

或

Picasso.with(itemView.getContext().getApplicationContext()).load(al_prod_image.get(i))

Answer 4

最简单的解决方案是使用 viewHolder.itemView.getContext()

Picasso.with(viewHolder.itemView.getContext()).load(al_prod_image.get(i))
                   .placeholder(R.drawable.floatingicon)
                   .error(R.drawable.floatingicon).
                   .into(viewHolder.img_prod);

Answer 5

来自 Activity,

 RecyclerView.Adapter adapter = new DataAdapter(YOUR_ACTIVITY.this, al_prod_id,al_prod_name, al_prod_price,al_prod_image);

在适配器中，

   private Context context;

public DataAdapter(Context mContext, ArrayList<String> al_prod_id, ArrayList<String> al_prod_name, ArrayList<String> al_prod_price, ArrayList<String> al_prod_image) {
     this.context= mContext;
     this.al_prod_id = al_prod_id;
     this.al_prod_price = al_prod_price;
     this.al_prod_name = al_prod_name;
     this.al_prod_image = al_prod_image
 }

在 Picasso 的上下文中使用它

Picasso.with(context).load(al_prod_image.get(i))
                   .placeholder(R.drawable.floatingicon)
                   .error(R.drawable.floatingicon).
                   .into(viewHolder.img_prod);

Answer 6

将您的 activity 上下文传递给 DataAdapter

RecyclerView.Adapter adapter = new  DataAdapter(yourActivity.this,al_prod_id,al_prod_name,
                   al_prod_price,al_prod_image);

数据适配器

private Context mContext;
private ArrayList<String> al_prod_name,al_prod_price,al_prod_id,al_prod_image;

public DataAdapter(Context mContext,ArrayList<String> al_prod_id,  ArrayList<String> al_prod_name,ArrayList<String> al_prod_price, ArrayList<String> al_prod_image)
{
   this.mContext=mContext;
   this.al_prod_id = al_prod_id;
   this.al_prod_price = al_prod_price;
   this.al_prod_name = al_prod_name;
   this.al_prod_image = al_prod_image
}

//set image
  Picasso.with(mContext).load(al_prod_image.get(i))
                   .placeholder(R.drawable.floatingicon)
                   .error(R.drawable.floatingicon).
                   .into(viewHolder.img_prod);

Answer 7

像这样更改您的 DataAdapter 构造函数在您的适配器中创建一个 Context 对象 class 并像这样更改您的构造函数

 public DataAdapter(Context context,ArrayList<String> al_prod_id, 
                           ArrayList<String> al_prod_name,
                               ArrayList<String> al_prod_price, 
                                  ArrayList<String> al_prod_image) {
                                   this.al_prod_id = al_prod_id;
                                   this.al_prod_price = al_prod_price;
                                   this.al_prod_name = al_prod_name;
                                   this.al_prod_image = al_prod_image;
this.mContext = context;
                               }

如何将上下文传递给毕加索

How to pass context to Picasso

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