如何在回收站视图适配器中获取上下文

我试图使用picasso库能够加载url到imageView，但我无法获得context正确使用picasso库。

 public class FeedAdapter extends RecyclerView.Adapter<FeedAdapter.ViewHolder> { private List<Post> mDataset; // Provide a reference to the views for each data item // Complex data items may need more than one view per item, and // you provide access to all the views for a data item in a view holder public class ViewHolder extends RecyclerView.ViewHolder { // each data item is just a string in this case public TextView txtHeader; public ImageView pub_image; public ViewHolder(View v) { super(v); txtHeader = (TextView) v.findViewById(R.id.firstline); pub_image = (ImageView) v.findViewById(R.id.imageView); } } // Provide a suitable constructor (depends on the kind of dataset) public FeedAdapter(List<Post> myDataset) { mDataset = myDataset; } // Create new views (invoked by the layout manager) @Override public FeedAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { // create a new view View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.feedholder, parent, false); // set the view's size, margins, paddings and layout parameters ViewHolder vh = new ViewHolder(v); return vh; } // Replace the contents of a view (invoked by the layout manager) @Override public void onBindViewHolder(ViewHolder holder, int position) { // - get element from your dataset at this position // - replace the contents of the view with that element holder.txtHeader.setText(mDataset.get(position).getPost_text()); Picasso.with(this.context).load("http://i.imgur.com/DvpvklR.png").into(holder.pub_image); } // Return the size of your dataset (invoked by the layout manager) @Override public int getItemCount() { return mDataset.size(); } } 

Answer 1

这里有几个选项：

1. 将Context作为parameter passing给FeedAdapter并将其保留为类字段
2. 在需要时使用dependency injection来注入Context 。 我强烈build议阅读一下。 有一个很好的工具 – Square的Dagger

3. 从任何View对象获取它。 在你的情况下，这可能适合你：

   holder.pub_image.getContext()

   由于pub_image是一个ImageView 。

Answer 2

你可以添加全局variables：

 private Context context; 

然后从这里分配上下文：

 @Override public FeedAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,int viewType) { // create a new view View v=LayoutInflater.from(parent.getContext()).inflate(R.layout.feedholder, parent, false); // set the view's size, margins, paddings and layout parameters ViewHolder vh = new ViewHolder(v); // set the Context here context = parent.getContext(); return vh; } 

快乐的Codding 🙂

Answer 3

您可以使用pub_image上下文（ holder.pub_image.getContext() ）：

 @Override public void onBindViewHolder(ViewHolder ViewHolder, int position) { holder.txtHeader.setText(mDataset.get(position).getPost_text()); Picasso.with(holder.pub_image.getContext()).load("http://i.imgur.com/DvpvklR.png").into(holder.pub_image); } 

Answer 4

你可以像这样使用view.getContext（）

例

 holder.tv_room_name.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Toast.makeText(v.getContext(), "", Toast.LENGTH_SHORT).show(); } }); 

Answer 5

首先全球申报

Context mContext;

通过修改构造函数传递上下文。

 public FeedAdapter(List<Post> myDataset, Context context) { mDataset = myDataset; this.mContext = context; } 

然后使用mContext你需要它

Answer 6

创build一个FeedAdapter的构造函数：

 Context context; //global public FeedAdapter(Context context) { this.context = context; } 

并在活动

 FeedAdapter obj = new FeedAdapter(this); 

Answer 7

首先添加一个全局variables

 Context mContext; 

然后改变你的构造函数

 public FeedAdapter(Context context, List<Post> myDataset) { mContext = context; mDataset = myDataset; } 

在创build适配器时传递你的上下文。

 FeedAdapter myAdapter = new FeedAdapter(this,myDataset); 

Answer 8

你可以使用这个：

 itemView.getContext()