Android控件之ListView探究二
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
参考文档：
android常用控件