关于ListView和Adapter

未优化的Adapter

import java.util.List; import ouc.sei.proandroid.R; import android.content.Context; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.TextView; public class MyAdapter2 extends BaseAdapter { private List<String> lists; private Context context; public MyAdapter2(List<String> lists, Context context) { this.lists = lists; this.context = context; } @Override public int getCount() { // TODO Auto-generated method stub return lists.size(); } @Override public Object getItem(int position) { // TODO Auto-generated method stub return lists.get(position); } @Override public long getItemId(int position) { // TODO Auto-generated method stub return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { // TODO Auto-generated method stub TextView textView; int type = getItemViewType(position); System.out.println("getView " + position + " " + convertView + " type = " + type); convertView = View.inflate(context, R.layout.list_item, null); textView = (TextView) convertView.findViewById(R.id.textView); convertView.setTag(textView); textView.setText(lists.get(position)); return convertView; } }

这个Adapter对Item的每次请求都想getView请求生成一个convertView实例以返回。也就是说，如果有1亿个item，那么每次页面翻滚到这个Item时，convertView都会生成一个实例View，这样的代码是非常的耗内存的。

优化代码如下：

import java.util.List; import ouc.sei.proandroid.R; import android.content.Context; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.TextView; public class MyAdapter extends BaseAdapter { private List<String> lists; private Context context; public MyAdapter(List<String> lists,Context context){ this.lists = lists; this.context = context; } @Override public int getCount() { // TODO Auto-generated method stub return lists.size(); } @Override public Object getItem(int position) { // TODO Auto-generated method stub return lists.get(position); } @Override public long getItemId(int position) { // TODO Auto-generated method stub return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { // TODO Auto-generated method stub TextView textView; int type = getItemViewType(position); System.out.println("getView " + position + " " + convertView + " type = " + type); if (convertView == null){ convertView = View.inflate(context, R.layout.list_item, null); textView = (TextView) convertView.findViewById(R.id.textView); convertView.setTag(textView); } else { textView = (TextView) convertView.getTag(); } textView.setText(lists.get(position)); return convertView; } } 以上代码使用了复用的思想，首次请求时，首先显示一屏幕的Item，并建立实例，当Item1消失，Item10出现，则Item10会复用Item1的实例。如图：

参考：http://android.amberfog.com/?p=296