Android学习笔记_11_ListView控件使用

一、界面设计：

　　1、activity_main.xml文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >

    <LinearLayout 

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:orientation="horizontal" >

    

        <TextView

            android:layout_width="120dp"

            android:layout_height="wrap_content"

            android:text="@string/name" />

          <TextView

            android:layout_width="match_parent"

            android:layout_height="wrap_content"

            android:text="@string/age" />

    </LinearLayout>



    <ListView

        android:id="@+id/listView"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:layout_marginTop="20dp" >



    </ListView>



</RelativeLayout>

View Code

　　2、item.xml文件：用于显示每一行的内容

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="horizontal" >

    

    <TextView

        android:id="@+id/name"

        android:layout_width="120dp"

        android:layout_height="wrap_content"

        />

      <TextView

        android:id="@+id/age"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        />

</LinearLayout>

View Code

　　3、最终测试界面：

　　每行显示用户名称和年龄。

二、三种方式将数据绑定到ListView控件上：

package com.example.listview;



import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;



import android.app.Activity;

import android.database.Cursor;

import android.os.Bundle;

import android.support.v4.widget.SimpleCursorAdapter;

import android.view.Menu;

import android.view.View;

import android.widget.AdapterView;

import android.widget.AdapterView.OnItemClickListener;

import android.widget.ListView;

import android.widget.SimpleAdapter;

import android.widget.Toast;



import com.example.entity.Person;

import com.example.lservice.DBPersonService;

import com.example.lservice.PersonAdapter;



public class MainActivity extends Activity {



    private ListView listView;

    private DBPersonService personService;



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        listView = (ListView) this.findViewById(R.id.listView);

        personService = new DBPersonService(this);

　　　　 //监听行点击事件
        listView.setOnItemClickListener(new OnItemClickListener() {

            //parent:指当前被点击条目的listview view：指当前被点击的条目 position:被点击条目的索引

              @Override

            public void onItemClick(AdapterView<?> parent, View view,

                    int position, long id) {

                ListView lv = (ListView) parent;

                /*

                 * 1、自定义适配器当前条目是Person对象。

                    * 2、采用SimpleCursorAdapter适配器，返回的是Cursor对象。

                    * 3、采用SimpleAdapter适配器，返回的是HashMap<String, Object>对象。

                   */

                Person p = (Person) lv.getItemAtPosition(position);

                String info = p.getName() + " " + position + " " + id;

                Toast.makeText(getApplicationContext(), info, 1).show();



            }



        });

        show3();

    }



    //第一种： 使用SimpleAdapter作为适配器

    private void show() {

        List<Person> persons = personService.getScrollData(0, 20);

        List<HashMap<String, Object>> data = new ArrayList<HashMap<String, Object>>();

        for (Person person : persons) {

            HashMap<String, Object> map = new HashMap<String, Object>();

            map.put("name", person.getName());

            map.put("age", person.getAge());

            data.add(map);

        }

        SimpleAdapter adapter = new SimpleAdapter(this, data, 

                R.layout.item,// 就是一个界面显示文件item.xml

                new String[] { "name", "age" },//from： 从结果集中获取数据，将需要显示的数据列名放到该集合

                new int[] { R.id.name, R.id.age }// to:将结果集的数据字段对应到listview（item.xml）上

        );

        listView.setAdapter(adapter);

    }



    //第二种： 使用SimpleCursorAdapter作为适配器

    private void show2() {

        Cursor cursor = personService.getCursorScrollData(0, 20);

        // 使用SimpleCursorAdapter适配器注意两个问题：

        // 1、返回的游标对象不能被关闭。

        // 2、查询语句字段必须有"_id"这个字段，例如：select id as _id,name,age from person。

        @SuppressWarnings("deprecation")

        SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,

                R.layout.item, cursor, new String[] { "name", "age" },

                new int[] { R.id.name, R.id.age });

        listView.setAdapter(adapter);

    }

    

    //第三种： 自定义适配器PersonAdapter

    private void show3() {

        List<Person> persons = personService.getScrollData(0, 10);

        PersonAdapter adapter = new PersonAdapter(this, persons, R.layout.item);

        listView.setAdapter(adapter);

    }



    

    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        getMenuInflater().inflate(R.menu.main, menu);

        return true;

    }



}

 

　　自定义适配器类实现：

package com.example.lservice;



import java.util.List;



import android.content.Context;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.BaseAdapter;

import android.widget.TextView;



import com.example.entity.Person;

import com.example.listview.R;



public class PersonAdapter extends BaseAdapter {

    //被绑定的数据

    private List<Person> persons;

    //绑定条目界面

    private int resource;

    //布局填充，作用是可以用xml文件生成View对象

    private LayoutInflater inflater;

    

    public PersonAdapter(Context context,List<Person> persons, int resource) {

        this.persons = persons;

        this.resource = resource;

        inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    }



    @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;

    }



    //会缓存之前的View

    @Override

    public View getView(int position, View convertView, ViewGroup parent) {

        TextView nameView =null;

        TextView ageView = null;

        if (convertView == null) {// 表示是第一页，需要创建该对象

            //生成条目界面对象

            convertView = inflater.inflate(resource, null);

             nameView = (TextView) convertView.findViewById(R.id.name);

             ageView = (TextView) convertView.findViewById(R.id.age);

            ViewCache cache = new ViewCache();

            cache.ageView=ageView;

            cache.nameView=nameView;

            //Tags can also be used to store data within a view without resorting to another data structure.

            convertView.setTag(cache);

        }else{

            ViewCache cache = (ViewCache) convertView.getTag();

            nameView = cache.nameView;

            ageView = cache.ageView;

        }

//        TextView nameView = (TextView) convertView.findViewById(R.id.name);

//        TextView ageView = (TextView) convertView.findViewById(R.id.age);

        Person person = persons.get(position);

        nameView.setText(person.getName());

        //setText方法：被设置的值要转换成字符串类型，否则出错

        ageView.setText(person.getAge().toString());

        

        return convertView;

    }

    /**

     * 由于每次都要查找View对象，因此就通过setTag将其保存起来。

     * @author Administrator

     *

     */

    private final class ViewCache{

        public TextView nameView;

        public TextView ageView;

        

    }

}