列表视图暂时冻结

Question

活动的ListView由自定义ArrayAdapter加载。当活动打开时，可以看到顶部一个和一半的列表视图项目 - 这对于高度来说可以。然而，当向下滚动时，在第三个项目被看到/加载之前的那一刻，活动暂时冻结。第三项完成装载后，根本不会冻结其他物品。什么会导致冻结？

这里是getView方法（没有什么可疑的，我认为）：

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 

    if (convertView instanceof LinearLayout) 
     return convertView; 

    LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    View rowView = inflater.inflate(R.layout.list_item_overview, parent, false); 

    TextView venueName = (TextView) rowView.findViewById(R.id.venueName); 
    TextView requestTime = (TextView) rowView.findViewById(R.id.requestTime); 
    TextView likeCount = (TextView) rowView.findViewById(R.id.likeCount); 
    TextView commentCount = (TextView) rowView.findViewById(R.id.commentCount); 
    TextView singerName = (TextView) rowView.findViewById(R.id.singerName); 
    TextView songName = (TextView) rowView.findViewById(R.id.songName); 

    venueName.setText(feeds.get(position).getVenue().getName()); 
    requestTime.setText(TimeUtil.getFeedItemRequestedTime(feeds.get(position).getRequested_at())); 
    likeCount.setText(Integer.toString(feeds.get(position).getLikes())); 
    commentCount.setText(Integer.toString(feeds.get(position).getComments())); 
    singerName.setText(feeds.get(position).getSong().getArtist()); 
    songName.setText(feeds.get(position).getSong().getTitle()); 


    return rowView; 
} 

Answer 1

原因之一，会人为增加每次的看法。在前几次之后，convertView已经被夸大了。另外，findViewById()是一个相当昂贵的电话。建议使用ViewHolder策略来减少呼叫。尝试改变，看看性能是否提高。

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 

    if (convertView instanceof LinearLayout) 
     return convertView; 

    View rowView = super.getView(position, convertView, parent); 

    ViewHolder holder = (ViewHolder)convertView.getTag(); 

    if (holder == null) { 
     holder = new ViewHolder(); 
     holder.venueName = (TextView) rowView.findViewById(R.id.venueName); 
     holder.requestTime = (TextView) rowView.findViewById(R.id.requestTime); 
     holder.likeCount = (TextView) rowView.findViewById(R.id.likeCount); 
     holder.commentCount = (TextView) rowView.findViewById(R.id.commentCount); 
     holder.singerName = (TextView) rowView.findViewById(R.id.singerName); 
     holder.songName = (TextView) rowView.findViewById(R.id.songName); 
     rowView.setTag(holder); 
    } 

    holder.venueName.setText(feeds.get(position).getVenue().getName()); 
    holder.requestTime.setText(TimeUtil.getFeedItemRequestedTime(feeds.get(position).getRequested_at())); 
    holder.likeCount.setText(Integer.toString(feeds.get(position).getLikes())); 
    holder.commentCount.setText(Integer.toString(feeds.get(position).getComments())); 
    holder.singerName.setText(feeds.get(position).getSong().getArtist()); 
    holder.songName.setText(feeds.get(position).getSong().getTitle()); 


    return rowView; 
} 

private static class ViewHolder { 
    TextView venueName, requestTime, likeCount, commentCount, 
     singerName, songName; 
}