listview改变字体大小实例讲解

package lt.com; 
import java.util.ArrayList; 
import java.util.HashMap; 
import java.util.List; 
import java.util.Map; 
import android.app.Activity; 
import android.app.AlertDialog; 
import android.app.ListActivity; 
import android.content.Context; 
import android.content.DialogInterface; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AdapterView; 
import android.widget.BaseAdapter; 
import android.widget.Button; 
import android.widget.ImageView; 
import android.widget.ListView; 
import android.widget.TextView; 
import android.widget.AdapterView.OnItemClickListener; 
public class ListText extends Activity { 
List<Map<String,Object>> mData; 
public static int select_item = -1; 
//MyAdapter adapter; 

/** Called when the activity is first created. */ 
@Override 
public void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.main); 
ListView lv=(ListView)findViewById(R.id.lv) ; 
mData= GetDate(); 
final MyAdapter adapter =new MyAdapter(this); 
lv.setAdapter(adapter); 
Log.v("tag", "100"); 
//点击事件 
lv.setOnItemClickListener(new OnItemClickListener(){ 

public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, 
long arg3) { 
select_item = arg2; //当前选择的item 
adapter.notifyDataSetChanged(); //通知adapter刷新数据 
Log.v("tag", "1"); 
} 
public void onNothingSelected(AdapterView<?> arg0) { 

} 

}); 
} 
//item相关信息 名称 图片 
public List<Map<String,Object>> GetDate(){ 

List<Map<String,Object>> list=new ArrayList<Map<String,Object>>(); //存在一个大仓库，摆放着很多抽屉 ，list相当把抽屉放进仓库。 
// 这是upcast 或者ArrayList<Map<String,Object>> list=new ArrayList<Map<String,Object>>();也行 

Map<String,Object> map=new HashMap<String,Object>();//抽屉，里面有东西。 
map.put("text", "中国");//把东西放到抽屉里面 
list.add(map);//把抽屉放到仓库里 

HashMap<String,Object> map1=new HashMap<String,Object>(); 
map1.put("text", "美国"); 
list.add(map1); 

HashMap<String,Object> map2=new HashMap<String,Object>(); 
map2.put("text", "日本"); 
list.add(map2); 

return list; 
} 
//自定义适配器 
public class MyAdapter extends BaseAdapter{ 
private LayoutInflater mInflater;//Instantiates a layout XML file into its corresponding View objects. 
private int select_item; 
public MyAdapter(Context context){ 
this.mInflater = LayoutInflater.from(context);//Obtains the LayoutInflater from the given context. 
} 

//item的数量 
public int getCount() { 
// TODO Auto-generated method stub 
return mData.size(); 
} 
public Object getItem(int arg0) { 
// TODO Auto-generated method stub 
return null; 
} 
public long getItemId(int position) { 
// TODO Auto-generated method stub 
return 0; 
} 
//convertView是复用的view，如果没有旧的就新建个新的view；parent是listview 
public View getView(int position, View convertView, ViewGroup parent) { 
// TODO Auto-generated method stub 
ViewHolder holder = null; 
if(convertView==null){ 
holder=new ViewHolder(); 
convertView=mInflater.inflate(R.layout.main, null);//Inflate a new view hierarchy from the specified xml resource. 
holder.texta = (TextView)convertView.findViewById(R.id.text); 
convertView.setTag(holder);//Sets the tag associated with this view ， A tag can be used to mark a view in its hierarchy and does not have to be unique within the hierarchy. 
//这个view是holder绘制的 
} 
else{ 
holder = (ViewHolder)convertView.getTag();//get tag 
} 
holder.texta.setText((String)mData.get(position).get("text")); 
this.select_item = ListText.select_item; 
try{ 
if(this.select_item == position){ 
holder.texta.setTextSize(50); //选中的Item字体：50px 
Log.v("tag", "3"); 
} 
else 
holder.texta.setTextSize(20); //未选中的Item字体：10px 
Log.v("tag", "2"); 
}catch(Exception ex){ 
ex.printStackTrace(); 
} 


return convertView; 
} 
} 
/** listView 中某项被选中后的逻辑 
protected void onListItemClick(ListView l, View v, int position, long id) { 
select_item = position; //当前选择的item 
// adapter.notifyDataSetChanged(); //通知adapter刷新数据 

Log.v("tag", "1"); 
} 
*/ 
public final class ViewHolder{ 
TextView texta; 

} 
} 

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="fill_parent" 
android:layout_height="fill_parent" 
android:orientation="vertical" > 
<ListView 
android:id="@+id/lv" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
> 
</ListView> 
<TextView 
android:id="@+id/text" 
android:layout_width="fill_parent" 
android:layout_height="wrap_content" 
/> 
</LinearLayout>