listview更改订单

Question

1. 我在自定义适配器中通过Picasso Library加载图像，然后将其显示在我的ListFragment中。当我尝试滚动时，某些图像更改顺序（我认为重复使用单元格是错误的）。

2. 什么是异步下载图像的最佳地点？我使用viewholder在自定义适配器中执行此操作。

   public class PostsAdapter extends BaseAdapter { 
   private static final String TAG = "tag.example.tag"; 
   private static final String URL_PREFIX = "http://someapi.com/v1/api/"; 
   private Context mContext; 
   private ArrayList<Post> mData; 
   private static LayoutInflater inflater = null; 
   
   public PostsAdapter(Context context, ArrayList<Post> data) { 
       mContext = context; 
       mData = data; 
       inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) 
   } 
   
   @Override 
   public boolean isEnabled(int position) { 
       return true; 
   } 
   
   @Override 
   public int getCount() { 
       return mData.size(); 
   } 
   
   @Override 
   public Object getItem(int i) { 
       return i; 
   } 
   
   @Override 
   public long getItemId(int i) { 
       return i; 
   } 
   
   @Override 
   public View getView(int i, View view, ViewGroup viewGroup) { 
       View v = view; 
       ViewHolder holder = null; 
       if(view == null) 
       v = inflater.inflate(R.layout.post_listviewrow, null); 
   
       holder = new ViewHolder(); 
   
       holder.imageView = (ImageView) v.findViewById(R.id.imageView); 
   
       Post post = (Post) mData.get(i); 
       // Download image with Picasso 
       holder.imageView.setTag(post.getPictureUrl()); 
       Picasso.with(mContext).load(URL_PREFIX + post.getPictureUrl()).into(holder.imageView); 
       return v; 
   } 
   
       static class ViewHolder { 
       TextView titleTextView; 
       ImageView imageView; 
       } 
   } 
   

Answer 1

SOLUTION： 更改getView方法是这样的

@Override 
public View getView(int i, View view, ViewGroup viewGroup) { 

    final ViewHolder holder; 

    if(view == null) { 
     view = inflater.inflate(R.layout.post_listviewrow, null); 
     holder = new ViewHolder(); 
     holder.imageView = (ImageView) view.findViewById(R.id.imageView); 
     holder.titleTextView = (TextView) view.findViewById(R.id.textview); 
     holder.progressBar = (ProgressBar) view.findViewById(R.id.progressBar); 


     view.setTag(holder); 
    } else { 
     holder = (ViewHolder) view.getTag(); 
    } 
     // Get position 
     Post post = (Post) mData.get(i); 

     holder.titleTextView.setText(post.getTitle()); 
     Picasso picasso = Picasso.with(mContext); 
     picasso.setIndicatorsEnabled(true); 
     holder.progressBar.setVisibility(View.VISIBLE); 
     picasso.load(URL_PREFIX + post.getPictureUrl()) 
       .placeholder(R.drawable.placeholder) 
       .fit() 
       .centerCrop() 
       .into(holder.imageView, new Callback() { 
        @Override 
        public void onSuccess() { 
         holder.progressBar.setVisibility(View.GONE); 
        } 
        @Override 
        public void onError() {} 
     }); 

    return view; 
} 
static class ViewHolder { 

    TextView titleTextView; 
    ImageView imageView; 
    ProgressBar progressBar; 

} 

无论如何，你认为适配器是将下载任务的正确的地方？