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>

　　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>

　　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;
        
    }
}