对于ListView的一些用法（一）-白红宇

对于ListView的一些用法（一）

阅读量：4654 次

发布时间：2019-06-09

本文共 14460 字，大约阅读时间需要 48 分钟。

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

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

item.xml

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
     
       data = new ArrayList
      
       ();        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
       
         data;        private Context context;        private LayoutInflater mInflater;                public MyAdapter(List
        
          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

item.xml

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
     
       queryFriendsLimit(int startIndex, int block) {        List
      
        infos = new ArrayList
       
        ();        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
     
       infos;    private LayoutInflater mInflater;    public void setInfos(List
      
        infos) {        this.infos = infos;    }    public MyAdapter(List
       
         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
     
       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
      
        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;            }        }    }}

转载于:https://www.cnblogs.com/clarencezzh/p/5225440.html

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