比如listview的item里面含有姓名、年龄和头像;我想让姓名和年龄实时刷新数据,头像不刷新,怎么用代码实现啊?
实现的方式参见下面的示例:
public class ParticalRefreshActivity extends ListActivity {
String[] contents = new String[]{"aa","bb","cc","dd","ee","ff","gg","hh","ii","jj","kk","ll","mm","nn","oo","pp","qq","rr","ss","tt","uu","vv","ww","xx","yy","zz"};
ParticalRefreshAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mAdapter = new ParticalRefreshAdapter(this,contents);
setListAdapter(mAdapter);
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
mAdapter.refreshFixPosition(position);
}
class ParticalRefreshAdapter extends BaseAdapter{
public String[] contents;
LayoutInflater mInflater;
public ParticalRefreshAdapter(Context context,String[] contents){
this.contents = contents;
mInflater = LayoutInflater.from(context);
}
@Override
public int getCount() {
return contents.length;
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
//局部刷新的代码
public void refreshFixPosition(int position){
//刷新局部的item
ViewHolder holder = map.get(position);
String text = holder.textView.getText().toString().trim();
holder.textView.setText(text+"-");
//更改数据源,防止滑动时数据错误
contents[position] = text+"-";
}
public Map<Integer,ViewHolder> map = new HashMap<>();
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if(convertView == null) {
convertView = mInflater.inflate(R.layout.item_partical_refresh, null);
holder = new ViewHolder();
holder.textView = (TextView) convertView.findViewById(R.id.tv_partical_refresh);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.textView.setText(contents[position]);
map.put(position, holder);
return convertView;
}
class ViewHolder{
TextView textView;
}
}
}
如果确实如你所说,item数目也没有变化,直接添加监听器,在里面更新就行了啊。
更改数据源里的年龄姓名,然后notifyDataSetChanged
局部更新终究还是要伴随着listview的全局更新的,想想你局部更新,虽然可以内置什么监听器之类的对可视范围内的item进行控件的更新,但当你的item滑动滚出可视范围再滑回来,由于contentView的回收机制,你之前所做的更新将被重置到最初的状态,这时候往往你会考虑要弄一个记录的东西来记录之前修改的item的位置,还有一堆item上的控件的状态,还要对各种状态进行判断,复杂度不见得比全局更新代价小。而全局更新,你只需要根据item的位置修改和adapter绑定的数据集合中对应位置的数据实体,再调nodifyDataSetChanged来更新listview即可,虽然这样是全局更新,但不会引起listview的滚动,用户是感知不到是整体在刷新的。