ListView详解之六

Adapter是ListView和数据源之间的桥梁,当每条数据进入可见区时，adapter会调用其getView()方法，并返回代表具体数据的视图。滚动的时候频繁调用，支持成千上万的数据。重写的getView方法有如下几种形式：

public void getView(int position , View convertView , ViewGroup parent)
{       
 View item = mInflater.inflate(R.layout.list_view, null); 
 (TextView)item.findViewById(R.id.text).setText(DATA[position]);
 (ImageView)item.findViewById(R.id.img).setImageBitmap(icon); 
return item;    
}

public void getView(int position , View convertView , ViewGroup parent)
{        
    if(convertView == null){
          convertView = mInflater.inflate(R.layout.list_view, null);        
    }　　　　　　
   (TextView)convertView.findViewById(R.id.text).setText(DATA[position]);　
　 (ImageView)convertView.findViewById(R.id.img).setImageBitmap(icon);
    return convertView;
 }

static class ViewHolder
{        
    private TextView tv;
    private ImageView iv;
}        
public void getView(int position , View convertView , ViewGroup parent)
{        
    ViewHolder holder;        
   if(convertView == null)
   {            
      convertView = mInflater.inflate(R.layout.list_view, null); 
      holder = new ViewHolder();
      holder.tv = (TextView)convertView.findViewById(R.id.text); 
      holder.iv = (ImageView)convertView.findViewById(R.id.img);            
      convertView.setTag(holder); 
    }else{            
          holder = (ViewHolder) convertView.getTag();
     }        
    holder.tv.setText(DATA[position]);
    holder.iv.setImageBitmap(icon);        
    return convertView;   
}

这三种方式，从前往后效率依次提高！