对于ListView的一些用法（一）

2023-01-02 13:50:01

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;

            }

        }

    }

}

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