ListView显示数据库的数据-采用自定义布局-向上滑动可以加载更多数据

Posted 2022-09-22 Veer Han

本案例使用自定义布局实现在ListView中显示数据库的数据(用户名、手机号)的功能，ListView向上滑动可以加载更多数据。

1.user_item.xml

<?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/tv_name"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginLeft="10dp"
        android:layout_weight="1"
        android:text="chj" />

    <TextView
        android:id="@+id/tv_phone"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:text="13527168697" />

    <Button
        android:id="@+id/btn_call"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="拨号" />

    <Button
        android:id="@+id/btn_sms"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="信息" />

</LinearLayout>

2.在activity_main.xml中添加ListView控件 id=”@+id/lv_users”

3.自定义的adapter UserAdapter.java

package com.example.dbhytc.adapter;

import java.util.List;
import java.util.Map;

import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import com.example.dbhytc.R;
import com.example.dbhytc.SmsActivity;

public class UserAdapter extends BaseAdapter 

    private Context context;
    private List<Map<String, Object>> data;
    private ViewHolder viewHolder;

    public UserAdapter(Context context, List<Map<String, Object>> data) 
        this.context = context;
        this.data = data;
    

    @Override
    public int getCount() 
        // TODO Auto-generated method stub
        return data.size();
    

    @Override
    public Object getItem(int position) 
        // TODO Auto-generated method stub
        return data.get(position);
    

    @Override
    public long getItemId(int position) 
        // TODO Auto-generated method stub
        return position;
    

    @Override
    public View getView(int position, View convertView, ViewGroup parent) 

        if (convertView == null) 
            viewHolder = new ViewHolder();
            convertView = View.inflate(context, R.layout.user_item, null);
            viewHolder.tv_name = (TextView) convertView
                    .findViewById(R.id.tv_name);
            viewHolder.tv_phone = (TextView) convertView
                    .findViewById(R.id.tv_phone);
            viewHolder.btn_call = (Button) convertView
                    .findViewById(R.id.btn_call);
            viewHolder.btn_sms = (Button) convertView
                    .findViewById(R.id.btn_sms);

            convertView.setTag(viewHolder);
         else 
            viewHolder = (ViewHolder) convertView.getTag();
        

        // 赋值
        Map map = data.get(position);
        viewHolder.tv_name.setText(map.get("name").toString());
        final String phone = map.get("phone").toString();
        viewHolder.tv_phone.setText(phone);

        viewHolder.btn_call.setOnClickListener(new OnClickListener() 

            @Override
            public void onClick(View v) 
                Toast.makeText(context, "打电话", 1).show();
                Intent intent = new Intent(Intent.ACTION_CALL, Uri.parse("tel:"
                        + phone));
                context.startActivity(intent);
            
        );

        viewHolder.btn_sms.setOnClickListener(new OnClickListener() 

            @Override
            public void onClick(View v) 
                Toast.makeText(context, "发信息", 1).show();
                // 执行一个意图 打开发短信界面
                // 1.定义一个意图
                Intent intent = new Intent(context, SmsActivity.class);
                // 通过这个意图可以附带数据
                intent.putExtra("phone", phone);
                // 2.执行意图
                context.startActivity(intent);
            
        );

        return convertView;
    

    class ViewHolder 
        public TextView tv_name, tv_phone;
        public Button btn_call, btn_sms;

    

4.HytcSQLiteOpenHelper.java

package com.example.dbhytc.db;

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

public class HytcSQLiteOpenHelper extends SQLiteOpenHelper


    //数据库的名称
    private static String name="hytc.db";
    //数据库的版本
    private static Integer version=2;

    /**
     * 只需保证 在实例化子类对象时，保证父类对象先实例化
     * @param context
     */
    public HytcSQLiteOpenHelper(Context context) 
        super(context, name, null, version);
    

    /**
     * 第一次执行的时候创建数据库
     */
    @Override
    public void onCreate(SQLiteDatabase db) 
       db.execSQL("CREATE TABLE user (id integer primary key autoincrement, name varchar(20))");
    

    /**
     * 当版本号发生变化的时候 触发
     */
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
        db.execSQL("alter table user add column phone varchar(11)");

    

5.UserDao中定义了查询数据data集合的方法getObjects()及得到总页数的方法getPages()

package com.example.dbhytc.dao;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

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

import com.example.dbhytc.db.HytcSQLiteOpenHelper;

public class UserDao 

    // 数据库管理操作对象
    private HytcSQLiteOpenHelper helper;
    private List<Map<String, Object>> data;
    private int pagesize = 12;

    public UserDao(List<Map<String, Object>> data, Context context) 
        this.data = data;
        helper = new HytcSQLiteOpenHelper(context);
    

    /**
     * 查询方法
     */

    public void getObjects(Integer nowpage) 
        // 获取SQLiteDatabase对象
        SQLiteDatabase db = helper.getReadableDatabase();
        // 计算开始的记录数
        int startSize = (nowpage - 1) * pagesize;
        Cursor c = db.rawQuery("select id,name,phone from user limit ?,?",
                new String[]  startSize + "", pagesize + "" );

        while (c.moveToNext()) 
            Map<String, Object> map = new HashMap<String, Object>();
            map.put("name", c.getString(c.getColumnIndex("name")));
            map.put("phone", c.getString(c.getColumnIndex("phone")));
            map.put("id", c.getInt(c.getColumnIndex("id")));
            data.add(map);
        
        c.close();
        db.close();

    

    public int getPages() 
        int pages = 0;
        // 获取SQLiteDatabase对象
        SQLiteDatabase db = helper.getReadableDatabase();
        // 计算开始的记录数
        Cursor c = db.rawQuery("select count(*) as c from user", null);
        if (c.moveToNext()) 
            int count = c.getInt(c.getColumnIndex("c"));
            //计算总页数
            pages = count % pagesize == 0 ? count / pagesize : count / pagesize
                    + 1;
        
        c.close();
        db.close();
        return pages;
    

6.MainActivity.java

package com.example.dbhytc;

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

import android.app.Activity;
import android.os.Bundle;
import android.view.ViewTreeObserver.OnScrollChangedListener;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;

import com.example.dbhytc.adapter.UserAdapter;
import com.example.dbhytc.dao.UserDao;

public class MainActivity extends Activity implements OnScrollListener 

    // 声明控件
    private ListView lv_users;

    private UserDao userDao;
    private List<Map<String, Object>> data = new ArrayList<Map<String, Object>>();

    private int nowpage = 1;

    private boolean isLastRow = false;

    private UserAdapter adapter;

    private int pages;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 获取控件对象
        lv_users = (ListView) findViewById(R.id.lv_users);

        // 数据
        userDao = new UserDao(data, this);
        // 查询出总页数
        pages = userDao.getPages();
        userDao.getObjects(nowpage);

        adapter = new UserAdapter(this, data);

        // 设置适配器
        lv_users.setAdapter(adapter);

        // 注册事件监听 滚动的事件
        lv_users.setOnScrollListener(this);
    

    /**
     * 当scrollstate改变的时候 都会触发该函数 scrollstate 0 空闲 1滚动 2抛 1 0 1 2 0
     */

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) 

        // 判断是否是最后一行
        if (isLastRow) 
            // 再判断是否停止滚动
            if (scrollState == SCROLL_STATE_IDLE) 
                // pages = userDao.getPages();
                if (nowpage < pages) 
                    // 让当前页加1
                    nowpage = nowpage + 1;
                    // 假设往这个集合中添加数据
                    userDao.getObjects(nowpage);
                    // 通知变化
                    adapter.notifyDataSetChanged();
                
            
            // 改变值
            isLastRow = false;
        

    

    /**
     * 当滚动的时候触发的函数 firstVisibleItem:条目可见第一个位置值 visibleItemCount：条目可见的数量
     * totalItemCount data集合数量 条目总个数
     */
    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) 

        // 判断
        if ((firstVisibleItem + visibleItemCount) >= totalItemCount) 
            isLastRow = true;