1.使用场景
在重写ListView的BaseAdapter时，我们常常在getView()方法中复用convertView，以提高性能。convertView在Item为单一的同种类型布局时，能够回收并重用，但是多个Item布局类型不同时，convertView的回收和重用会出现问题。比如有些行为纯文本，有些行则是图文混排，这里纯文本行为一类布局，图文混排的行为第二类布局。单一类型的ListView很简单，下面着重介绍一下ListView包含多种类型视图布局的情形。
2.ListView包含不同Item的布局
我们需要做这些工作:
1）重写 getViewTypeCount() – 该方法返回多少个不同的布局
2）重写 getItemViewType(int) – 根据position返回相应的Item
3）根据view item的类型，在getView中创建正确的convertView
3.案例
import java.util.ArrayList;import android.app.Activity; import android.content.Context; import android.os.Bundle; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.CheckBox; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.ListView; import android.widget.TextView;public class listViewTest extends Activity { ListView listView;MyAdapter listAdapter;ArrayList listString;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);listView = (ListView)this.findViewById(R.id.listview);listString = new ArrayList();for(int i = 0 ; i < 100 ; i++){listString.add(Integer.toString(i));}listAdapter = new MyAdapter(this);listView.setAdapter(listAdapter);}class MyAdapter extends BaseAdapter{Context mContext;LinearLayout linearLayout = null;LayoutInflater inflater;TextView tex;final int VIEW_TYPE = 3;final int TYPE_1 = 0;final int TYPE_2 = 1;final int TYPE_3 = 2;public MyAdapter(Context context) {// TODO Auto-generated constructor stubmContext = context;inflater = LayoutInflater.from(mContext);}@Overridepublic int getCount() {// TODO Auto-generated method stubreturn listString.size();}//每个convert view都会调用此方法，获得当前所需要的view样式@Overridepublic int getItemViewType(int position) {// TODO Auto-generated method stubint p = position%6;if(p == 0)return TYPE_1;else if(p < 3)return TYPE_2;else if(p < 6)return TYPE_3;elsereturn TYPE_1;}@Overridepublic int getViewTypeCount() {// TODO Auto-generated method stubreturn 3;}@Overridepublic Object getItem(int arg0) {// TODO Auto-generated method stubreturn listString.get(arg0);}@Overridepublic long getItemId(int position) {// TODO Auto-generated method stubreturn position;}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {// TODO Auto-generated method stubviewHolder1 holder1 = null;viewHolder2 holder2 = null;viewHolder3 holder3 = null;int type = getItemViewType(position);//无convertView，需要new出各个控件if(convertView == null){ Log.e("convertView = ", " NULL");//按当前所需的样式，确定new的布局switch(type){case TYPE_1:convertView = inflater.inflate(R.layout.listitem1, parent, false);holder1 = new viewHolder1();holder1.textView = (TextView)convertView.findViewById(R.id.textview1);holder1.checkBox = (CheckBox)convertView.findViewById(R.id.checkbox);Log.e("convertView = ", "NULL TYPE_1");convertView.setTag(holder1);break;case TYPE_2:convertView = inflater.inflate(R.layout.listitem2, parent, false);holder2 = new viewHolder2();holder2.textView = (TextView)convertView.findViewById(R.id.textview2);Log.e("convertView = ", "NULL TYPE_2");convertView.setTag(holder2);break;case TYPE_3:convertView = inflater.inflate(R.layout.listitem3, parent, false);holder3 = new viewHolder3();holder3.textView = (TextView)convertView.findViewById(R.id.textview3);holder3.imageView = (ImageView)convertView.findViewById(R.id.imageview);Log.e("convertView = ", "NULL TYPE_3");convertView.setTag(holder3);break;}}else{//有convertView，按样式，取得不用的布局switch(type){case TYPE_1:holder1 = (viewHolder1) convertView.getTag();Log.e("convertView !!!!!!= ", "NULL TYPE_1");break;case TYPE_2:holder2 = (viewHolder2) convertView.getTag();Log.e("convertView !!!!!!= ", "NULL TYPE_2");break;case TYPE_3:holder3 = (viewHolder3) convertView.getTag();Log.e("convertView !!!!!!= ", "NULL TYPE_3");break;}}//设置资源switch(type){case TYPE_1:holder1.textView.setText(Integer.toString(position));holder1.checkBox.setChecked(true);break;case TYPE_2:holder2.textView.setText(Integer.toString(position));break;case TYPE_3:holder3.textView.setText(Integer.toString(position));holder3.imageView.setBackgroundResource(R.drawable.icon);break;}return convertView;}}//各个布局的控件资源class viewHolder1{CheckBox checkBox;TextView textView;}class viewHolder2{TextView textView;}class viewHolder3{ImageView imageView;TextView textView;} }