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