对于ListView的一些用法（一）

• ScrollView：只能用于控件比较少的界面，如果数据有上千上万条，那么使用ScrollView就不好了，因为ScrollView就把所有的控件进行初始化，这是非常消耗性能的操作，所以android就设计了一个类ListView来专门处理列表数据条目的显示。
• ListView：处理条目比较多，并且每个条目都非常相似的场景。就是一个条目控件，会自动回收没有在屏幕上显示的控件，来优化性能。

对于ListView和BaseAdapter

1简单的用法

MainActivity.java

package com.example.listview;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
public class MainActivity extends Activity {
    protected static final String TAG = "MainActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //找到ListView
        ListView lv = (ListView) findViewById(R.id.lv);
        //给ListView设置数据(设置适配器     基本适配器)
        lv.setAdapter(new BaseAdapter() {
            //加工ListView需要的条目    int position 条目的下标
            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                Log.i(TAG, "position:"+position);
                TextView tv = new TextView(MainActivity.this);
                tv.setText("人生自古谁没有年轻的时候"+position);
                tv.setTextSize(20);
                return tv;
            }
            @Override
            public long getItemId(int position) {
                return 0;
            }
            @Override
            public Object getItem(int position) {
                return null;
            }
            //控制条目的数量
            @Override
            public int getCount() {
                return 100;
            }
        });
    }
}

activity_main.xml

<LinearLayout 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:orientation="vertical"
    tools:context=".MainActivity" >
    <ListView 
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </ListView>
</LinearLayout>

上图就是ListView控件的基本图像

2复杂ListView的用法

首先要创建一个ListView和一个条目上的内容

activity_main.xml

<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"
    tools:context=".MainActivity" >

    <ListView 
        android:layout_height="match_parent"
        android:layout_width="match_parent"
        android:id="@+id/lv">
    </ListView>

</RelativeLayout>

item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >
    
    <ImageView 
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher"
        android:layout_centerVertical="true"
        android:layout_marginRight="10dp"/>
    
    <TextView 
        android:id="@+id/tv_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/iv"
        android:layout_marginTop="10dp"
        android:textSize="22sp"
        android:text="姓名"/>
    <TextView 
        android:id="@+id/tv_age"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/iv"
        android:layout_below="@id/tv_name"
        android:textSize="16sp"
        android:text="年龄"/>

</RelativeLayout>

布局填充器layoutinflate：可以把res/layout下面的资源加载到内存，即可以把xml布局变成Java对象。一般就是加载item.xml上的东西

MainActivity.java

package com.example.listiview;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import cn.itcast.wh08.lv.domain.Teacher;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        ListView lv = (ListView) findViewById(R.id.lv);
        //模拟对象集合的数据 一般数据都是来自于网络，或者数据库       
        List<Teacher> data = new ArrayList<Teacher>();
        for(int i = 0;i<100;i++){
            data.add(new Teacher(i, "隔壁老王"+i, i+20));
        }
        //适配器
        MyAdapter adapter = new MyAdapter(data, this);
        //设置适配器
        lv.setAdapter(adapter);
    }

    //适配器
    private class MyAdapter extends BaseAdapter{
        private List<Teacher> data;
        private Context context;
        private LayoutInflater mInflater;
        
        public MyAdapter(List<Teacher> data, Context context) {
            super();
            this.data = data;
            this.context = context;
            //获取布局加载器
            mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }

        @Override
        public int getCount() {
            return data.size();
        }

        //返回条目指定位置的数据
        @Override
        public Object getItem(int position) {
            return data.get(position);
        }

        @Override
        public long getItemId(int position) {
            return 0;
        }

        //加工条目
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            //使用布局加载器加载布局
            View view = mInflater.inflate(R.layout.item, null);
            //找到条目对应的控件
            TextView tv_name = (TextView) view.findViewById(R.id.tv_name);
            TextView tv_age = (TextView) view.findViewById(R.id.tv_age);
            //获取条目对应的数据
            Teacher info = data.get(position);
            //把数据绑定给控件
            tv_name.setText(info.name);
            tv_age.setText(info.age+"");
            return view;
        }
        
    }

}

Teacher.java

package com.example.listview.vo;

public class Teacher {
    public int _id;
    public String _name;
    public int age;

    public Teacher(int _id, String _name, int age) {
        super();
        this._id = _id;
        this._name = _name;
        this.age = age;
    }

    public Teacher() {
        super();
    }
    
}

3.与数据库结合来显示

• mode 数据模型(数据) ：要被显示到ListView上的数据集合
• view 视图(展示数据) ： ListView
• controller控制层(把数据展示到空间上) : 适配器Adapter

我们还是要先建立ListView控件和item控件

activity_main.xml

<LinearLayout 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:orientation="vertical"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:paddingBottom="5dp"
        android:paddingTop="5dp"
        android:text="闺蜜列表"
        android:textSize="22sp" />

    <ListView
        android:id="@+id/lv"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />
- 

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/bt_pre"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:enabled="false"
            android:text="上一页" />

        <Button
            android:id="@+id/bt_next"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="下一页" />
    </LinearLayout>

</LinearLayout>

item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <ImageView
        android:id="@+id/iv_head"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher" />

    <TextView
        android:id="@+id/tv_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:layout_toRightOf="@id/iv_head"
        android:text="老师" />

    <TextView
        android:id="@+id/tv_phone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/tv_name"
        android:layout_toRightOf="@id/iv_head"
        android:text="13787009878" />

</RelativeLayout>

先建立一个数据库，为了得到数据。

MySqliteOpenHelper.java

package com.example.lisview.db;

import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class MySqliteOpenHelper extends SQLiteOpenHelper {

    private static SQLiteOpenHelper mInstance;

    public static synchronized SQLiteOpenHelper getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new MySqliteOpenHelper(context, "itcast.db", null, 1);
        }
        return mInstance;
    }

    public MySqliteOpenHelper(Context context, String name,
            CursorFactory factory, int version) {
        super(context, name, factory, version);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // 设计一个表
        db.execSQL("create table friends(_id integer primary key autoincrement,"
                + "name text," + "phone text)");
        // 初始化表数据
        ContentValues values = new ContentValues();
        for (int i = 0; i < 100; i++) {
            values.clear();
            values.put("name", "老师" + i);
            values.put("phone", "13787990" + i);
            db.insert("friends", null, values);
        }
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }

}

Friend.java

package com.example.lisview.vo;

public class Friend {
    public int _id;
    public String name;
    public String phone;
    public Friend(int _id, String name, String phone) {
        super();
        this._id = _id;
        this.name = name;
        this.phone = phone;
    }
    public Friend() {
        // TODO Auto-generated constructor stub
    }
}

对数据库的增、删、查、改

FriendDao.java

package com.example.lisview.dao;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import com.example.lisview.db.MySqliteOpenHelper;
import com.example.lisview.vo.Friend;

public class FriendDao {
    private Context context;
    private SQLiteOpenHelper helper;

    public FriendDao(Context context) {
        this.context = context;
        helper = MySqliteOpenHelper.getInstance(context);
    }
    
    /**
     * 获取数据的总条目
     * @return
     */
    public int queryAllSize(){
        int size = 0;
        SQLiteDatabase db = helper.getReadableDatabase();
        if(db.isOpen()){
            Cursor cursor = db.query("friends", new String[]{"*"}, null, null, null, null, null);
            size = cursor.getCount();//获取Cursor的大小
            cursor.close();
            db.close();
        }
        return size;
    }

    /**
     * 分页查询的
     * 
     * @param startIndex
     *            查询的开始下标
     * @param block
     *            每次查询的数据量
     * @return
     */
    public List<Friend> queryFriendsLimit(int startIndex, int block) {
        List<Friend> infos = new ArrayList<Friend>();
        SQLiteDatabase db = helper.getReadableDatabase();
        if (db.isOpen()) {
            Cursor cursor = db.query("friends", new String[] { "*" }, null,
                    null, null, null, null, startIndex + "," + block);
            while (cursor.moveToNext()) {
                int _id = cursor.getInt(0);
                String name = cursor.getString(1);
                String phone = cursor.getString(2);
                infos.add(new Friend(_id, name, phone));
            }
            cursor.close();
            db.close();
        }
        return infos;
    }
}

MyAdapter.java

package com.example.lisview.service;

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.lisview.R;
import com.example.lisview.vo.Friend;

public class MyAdapter extends BaseAdapter {
    private List<Friend> infos;
    private LayoutInflater mInflater;

    public void setInfos(List<Friend> infos) {
        this.infos = infos;
    }

    public MyAdapter(List<Friend> infos, Context context) {
        super();
        this.infos = infos;
        // 布局加载器
        mInflater = LayoutInflater.from(context);
    }

    // 返回条目的总数
    @Override
    public int getCount() {
        return infos.size();
    }

    // 得到item.xml代表的对象
    @Override
    public Object getItem(int position) {
        return infos.get(position);
    }

    // 得到Item的id，不过在这里貌似没有用
    @Override
    public long getItemId(int position) {
        return position;
    }

    // 得到Item的视图
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = mInflater.inflate(R.layout.item, null);
        TextView tv_name = (TextView) view.findViewById(R.id.tv_name);
        TextView tv_phone = (TextView) view.findViewById(R.id.tv_phone);

        Friend info = infos.get(position);

        tv_name.setText(info.name);
        tv_phone.setText(info.phone);
        return view;
    }

}

MainActivity.java

package com.example.lisview;

import java.util.List;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Button;
import android.widget.ListView;

import com.example.lisview.dao.FriendDao;
import com.example.lisview.service.MyAdapter;
import com.example.lisview.vo.Friend;

public class MainActivity extends Activity {

    private ListView lv;
    private Button bt_pre;
    private Button bt_next;
    private FriendDao friendDao;
    private int block = 10;// 每一页获取10条数据
    private int startIndex = 0;// 获取数据的下标
    private MyAdapter adapter;
    private int size;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
    }

    private void initView() {
        lv = (ListView) findViewById(R.id.lv);
        bt_pre = (Button) findViewById(R.id.bt_pre);
        bt_next = (Button) findViewById(R.id.bt_next);

        MyOnClickListener l = new MyOnClickListener();
        bt_pre.setOnClickListener(l);
        bt_next.setOnClickListener(l);

        friendDao = new FriendDao(this);
        size = friendDao.queryAllSize();
        // 查询第一页数据
        List<Friend> infos = friendDao.queryFriendsLimit(0, block);
        adapter = new MyAdapter(infos, this);
        lv.setAdapter(adapter);
        // 设置条目点击事件
        lv.setOnItemClickListener(new MyOnItemClickListener());
    }

    private class MyOnItemClickListener implements OnItemClickListener {

        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position,
                long id) {
            //获取条目的数据
            final Friend info = (Friend) adapter.getItem(position);
            //弹出对话框
            new AlertDialog.Builder(MainActivity.this)
            .setTitle(info.name)
            .setMessage("请选择操作")
            .setPositiveButton("打电话", new DialogInterface.OnClickListener() {
                
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    //打电话需要拨号权限
                    Intent intent = new Intent();
                    intent.setAction(Intent.ACTION_CALL);
                    intent.setData(Uri.parse("tel:"+info.phone));
                    startActivity(intent);
                }
            })
            .setNegativeButton("发短信", new DialogInterface.OnClickListener() {
                
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    //TODO:学员自己处理
                }
            })
            .show();
        }

    }

    private class MyOnClickListener  implements OnClickListener {

        @Override
        public void onClick(View v) {
            List<Friend> infos = null;
            switch (v.getId()) {
            case R.id.bt_pre:
                startIndex = startIndex - block;
                if (startIndex == 0) {
                    bt_pre.setEnabled(false);
                } else {
                    bt_pre.setEnabled(true);
                }
                bt_next.setEnabled(true);
                infos = friendDao.queryFriendsLimit(startIndex, block);
                adapter.setInfos(infos);// 把查询的数据设置给适配器
                // 刷新界面
                adapter.notifyDataSetChanged();
                break;

            case R.id.bt_next:
                startIndex = startIndex + block;
                // 判断是否是最后页面的数据
                // 现在页面的数据 startIndex=startIndex+block
                if ((startIndex + block) >= size) {
                    // 已经是最后一页数据
                    bt_next.setEnabled(false);
                } else {
                    bt_next.setEnabled(true);
                }
                bt_pre.setEnabled(true);
                infos = friendDao.queryFriendsLimit(startIndex, block);
                adapter.setInfos(infos);// 把查询的数据设置给适配器
                // 刷新界面
                adapter.notifyDataSetChanged();
                break;

            default:
                break;
            }
        }

    }

}