Android控件之ListView探究二

目录结构

main.xml布局文件

<?xml version="1.0" encoding="utf-8"?>
<!-- 使用相对布局 -->
<RelativeLayout
xmlns:android
="http://schemas.android.com/apk/res/android"
android:orientation
="vertical"
android:layout_width
="wrap_content"
android:layout_height
="wrap_content">
<TextView android:layout_width="100dip"
android:layout_height
="wrap_content"
android:layout_marginLeft
="30dip"
android:textSize
="20dip"
android:id
="@+id/id"/>
<TextView android:layout_width="100dip"
android:layout_height
="wrap_content"
android:layout_alignTop
="@id/id"
android:layout_toRightOf
="@id/id"
android:textSize
="20dip"
android:id
="@+id/name"/>
<TextView android:layout_width="wrap_content"
android:layout_height
="wrap_content"
android:layout_alignTop
="@id/name"
android:layout_toRightOf
="@id/name"
android:textSize
="20dip"
android:id
="@+id/age"/>
</RelativeLayout>

实体JavaBean

package com.ljq.domain;


public class Person {

private String id;
private String name;
private String age;

public Person() {
super();
}

public Person(String id, String name, String age) {
super();
this.id = id;
this.name = name;
this.age = age;
}

public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getAge() {
return age;
}

public void setAge(String age) {
this.age = age;
}
}

自定义适配器PersonAdapter

package com.ljq.ls;

import java.util.List;

import com.ljq.domain.Person;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;
/**
* ListView加载adapter的过程
*
* 1、先判断adapter有多少数据项,根据这个数据确定有多少个item
*
* 2、确定每个item里加载哪个view
*
* 3、在view里加载要显示的数据
*
*
@author jiqinlin
*
*/
public class PersonAdapter extends ArrayAdapter{
private LayoutInflater layoutInflater = null;
private List<Person> persons;

public PersonAdapter(Context context, int textViewResourceId, List objects) {
super(context, textViewResourceId, objects);
layoutInflater
= LayoutInflater.from(context);
persons
= objects;
}

/**
* 获取adapter里有多少个数据项
*/
@Override
public int getCount() {
return persons.size();
}

@Override
public Object getItem(int position) {
return persons.get(position);
}

@Override
public long getItemId(int position) {
return position;
}

/**
* 创建显示的数据界面
*
* Adapter的作用就是ListView界面与数据之间的桥梁,
* 当列表里的每一项显示到页面时,都会调用Adapter的getView方法返回一个View。
* 想过没有? 在我们的列表有1000000项时会是什么样的?是不是会占用极大的系统资源?
*/
@Override
public View getView(int position, View convertView, ViewGroup parent) {
/*
// 优化前
ViewHolder holder = new ViewHolder();
convertView = layoutInflater.inflate(R.layout.main, null);
holder.id = (TextView)convertView.findViewById(R.id.id);
holder.name = (TextView)convertView.findViewById(R.id.name);
holder.age = (TextView)convertView.findViewById(R.id.age);
convertView.setTag(holder);

holder.id.setText(persons.get(position).getId());
holder.name.setText(persons.get(position).getName());
holder.age.setText(persons.get(position).getAge());
return convertView;
*/

// 优化后
ViewHolder holder;
if(convertView == null){
convertView
= layoutInflater.inflate(R.layout.main, null);
holder
= new ViewHolder();
holder.id
= (TextView)convertView.findViewById(R.id.id);
holder.name
= (TextView)convertView.findViewById(R.id.name);
holder.age
= (TextView)convertView.findViewById(R.id.age);
convertView.setTag(holder);
}
else{
holder
= (ViewHolder)convertView.getTag();
}

holder.id.setText(persons.get(position).getId());
holder.name.setText(persons.get(position).getName());
holder.age.setText(persons.get(position).getAge());
return convertView;
}

/**
* 界面上的显示控件
*
*
@author jiqinlin
*
*/
private static class ViewHolder{
private TextView id;
private TextView name;
private TextView age;
}


}

类LsActivity

package com.ljq.ls;

import java.util.ArrayList;

import android.app.ListActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ListView;
import android.widget.Toast;

import com.ljq.domain.Person;

public class LsActivity extends ListActivity {
private ArrayList<Person> persons = new ArrayList<Person>();
private PersonAdapter personAdapter = null;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

initData();
personAdapter
=new PersonAdapter(LsActivity.this, R.layout.main, persons);
setListAdapter(personAdapter);
registerForContextMenu(getListView());
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
Person person
= persons.get(position);
Toast.makeText(LsActivity.
this, person.getId()+":"+person.getName()
+":"+person.getAge(), Toast.LENGTH_LONG).show();
return;
}

private void initData(){
persons.add(
new Person("序号", "姓名", "年龄"));
persons.add(
new Person("1", "ljq1", "20"));
persons.add(
new Person("2", "ljq2", "20"));
persons.add(
new Person("3", "ljq3", "20"));
persons.add(
new Person("4", "ljq4", "20"));
persons.add(
new Person("5", "ljq5", "20"));
persons.add(
new Person("6", "ljq6", "20"));
persons.add(
new Person("7", "ljq7", "20"));
persons.add(
new Person("8", "ljq8", "20"));
persons.add(
new Person("9", "ljq9", "20"));
}
}

运行结果

posted on 2011-02-23 14:58  Ruthless  阅读(8082)  评论(1编辑  收藏  举报