Android ListView 应用解析
在android开发中ListView是比较常用的组件，它以列表的形式展示具体内容，并且能够根据数据的长度自适应显示。抽空把对ListView的使用做了整理，并写了个小例子，如下图。
列表的显示需要三个元素：
1．ListVeiw 用来展示列表的View。
2．适配器 用来把数据映射到ListView上的中介。
3．数据 具体的将被映射的字符串，图片，或者基本组件。
根据列表的适配器类型，列表分为三种，ArrayAdapter，SimpleAdapter和SimpleCursorAdapter
现在项目的结构如下图所示：
main.xml如下所示：
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical" android:layout_width="fill_parent"android:layout_height="fill_parent"><LinearLayout android:orientation="horizontal"android:layout_width="fill_parent" android:layout_height="wrap_content"><TextView android:text="@string/name" android:layout_width="120dp"android:layout_height="wrap_content" /><TextView android:text="@string/phone" android:layout_width="fill_parent"android:layout_height="wrap_content" /></LinearLayout><ListView android:layout_width="fill_parent"android:layout_height="fill_parent" android:id="@+id/listView" /></LinearLayout>
item.xml如下图所示：
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="horizontal" android:layout_width="fill_parent"android:layout_height="fill_parent"><TextView android:id="@+id/name" android:layout_width="120dp"android:layout_height="wrap_content"/><TextView android:id="@+id/phone" android:layout_width="fill_parent"android:layout_height="wrap_content"/></LinearLayout>
string.xml
<?xml version="1.0" encoding="utf-8"?><resources> <string name="hello">Hello World, MainActivity!</string> <string name="app_name">数据库应用</string> <string name="name">姓名</string> <string name="phone">电话</string></resources>
cn.roco.db.domain.Person代码如下：
package cn.roco.db.domain;public class Person {public Person(Integer id, String name, String phone) {this.id = id;this.name = name;this.phone = phone;}public Person(String name, String phone) {this.name = name;this.phone = phone;}public Person() {}private Integer id;private String name;private String phone;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}@Overridepublic String toString() {// TODO Auto-generated method stubreturn "Person[id="+id+",name="+name+",phone="+phone+"]";}}package cn.roco.db.service;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DBOpenHelper extends SQLiteOpenHelper {public DBOpenHelper(Context context) {super(context,"roco.db", null, 2);}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL("CREATE TABLE person(personid integer primary key autoincrement,name varchar(20),phone varchar(20))");}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {db.execSQL("ALTER TABLE person ADD phone VARCHAR(12) NULL");}}
package cn.roco.db.serice;import java.util.List;import cn.roco.db.domain.Person;public interface IPersonService {public void save(Person person);public void delete(Integer id);public void update(Person person);public Person find(Integer id);public List<Person> getScrollData(int offset,int maxResult);public long getCount();}
package cn.roco.db.serice.imp;import java.util.ArrayList;import java.util.List;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import cn.roco.db.domain.Person;import cn.roco.db.serice.IPersonService;import cn.roco.db.service.DBOpenHelper;public class PersonServiceImp implements IPersonService {private DBOpenHelper dbOpenHelper;public PersonServiceImp(Context context) {this.dbOpenHelper = new DBOpenHelper(context);}/** * 添加记录 * @param person */@Overridepublic void save(Person person) {SQLiteDatabase db = dbOpenHelper.getWritableDatabase();db.execSQL("insert into person(name,phone) values(?,?)", new Object[] {person.getName(), person.getPhone() });}/** * 添加记录 * @param id */@Overridepublic void delete(Integer id) {SQLiteDatabase db = dbOpenHelper.getWritableDatabase();db.execSQL("delete from person where personid=?", new Object[] { id });}/** * 更新记录 * @param person */@Overridepublic void update(Person person) {SQLiteDatabase db = dbOpenHelper.getWritableDatabase();db.execSQL("update person set name=?,phone=? where personid=?",new Object[] { person.getName(), person.getPhone(),person.getId() });}/** * 查询记录 * @param id */@Overridepublic Person find(Integer id) {SQLiteDatabase db = dbOpenHelper.getReadableDatabase();Cursor cursor = db.rawQuery("select personid,name,phone from person where personid=?",new String[] { id.toString() });if (cursor.moveToFirst()) {int personid = cursor.getInt(cursor.getColumnIndex("personid"));String name = cursor.getString(cursor.getColumnIndex("name"));String phone = cursor.getString(cursor.getColumnIndex("phone"));return new Person(personid, name, phone);}cursor.close();return null;}/** * 分页获取几率 * @param offset 跳过前面多少条记录 * @param maxResult 每页获取多少条记录 * @return */@Overridepublic List<Person> getScrollData(int offset, int maxResult) {List<Person> persons = new ArrayList<Person>();SQLiteDatabase db = dbOpenHelper.getReadableDatabase();Cursor cursor = db.rawQuery("select * from person order by personid asc limit ?,?",new String[] { String.valueOf(offset),String.valueOf(maxResult) });while (cursor.moveToNext()) {int personid = cursor.getInt(cursor.getColumnIndex("personid"));String name = cursor.getString(cursor.getColumnIndex("name"));String phone = cursor.getString(cursor.getColumnIndex("phone"));persons.add(new Person(personid, name, phone));}cursor.close();return persons;}public Cursor getCursorScrollData(int offset, int maxResult) {List<Person> persons = new ArrayList<Person>();SQLiteDatabase db = dbOpenHelper.getReadableDatabase();Cursor cursor = db.rawQuery("select personid as _id, name, phone from person order by personid asc limit ?,?",new String[] { String.valueOf(offset),String.valueOf(maxResult) });return cursor;}/** * 获取记录总数 * @return */@Overridepublic long getCount() {SQLiteDatabase db = dbOpenHelper.getReadableDatabase();Cursor cursor = db.rawQuery("select count(*) from person ", null);cursor.moveToFirst();long result = cursor.getLong(0);cursor.close();return result;}}
MainActivity
package cn.roco.db;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import cn.roco.db.adapter.PersonAdapter;import cn.roco.db.domain.Person;import cn.roco.db.serice.imp.PersonServiceImp;import android.app.Activity;import android.database.Cursor;import android.os.Bundle;import android.view.View;import android.widget.AdapterView;import android.widget.AdapterView.OnItemClickListener;import android.widget.ListView;import android.widget.SimpleAdapter;import android.widget.SimpleCursorAdapter;import android.widget.Toast;public class MainActivity extends Activity {private ListView listView;private PersonServiceImp personService;/** Called when the activity is first created. */@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);personService = new PersonServiceImp(this);listView = (ListView) this.findViewById(R.id.listView);listView.setOnItemClickListener(new ItemClickListener());showByCursor();//showByList();//showByPersonAdapter();}/** *配置一个响应事件类 */private final class ItemClickListener implements OnItemClickListener{@Overridepublic void onItemClick(AdapterView<?> parent, View view, int position,long id) {ListView lView=(ListView) parent;/** * 对应自定义适配器 *///Person person= (Person) lView.getItemAtPosition(position);//Toast.makeText(getApplicationContext(), "id="+person.getId(), 1).show();/** * 对应游标适配器 */Cursor cursor=(Cursor) lView.getItemAtPosition(position);int personid=cursor.getInt(cursor.getColumnIndex("_id"));Toast.makeText(getApplicationContext(), "id="+personid, 1).show();}}//使用自定义的适配器PersonAdapterprivate void showByPersonAdapter() {List<Person> persons=personService.getScrollData(0, 30);PersonAdapter adapter=new PersonAdapter(this, persons, R.layout.item);listView.setAdapter(adapter);}//使用游标适配器SimpleCursorAdapterprivate void showByCursor() {Cursor cursor = personService.getCursorScrollData(0, 30);/** * 注意该适配器中的cursor必须要包含 _id 字段 * 解决方法：select personid as _id ..... */SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,R.layout.item, cursor, new String[] { "name", "phone" },new int[] { R.id.name, R.id.phone });listView.setAdapter(adapter);}//使用简单适配器SimpleAdapterprivate void showByList() {List<Person> persons = personService.getScrollData(0, 30);/** * 将取出来的数据封装到 List<HashMap<String, Object>> 中 */List<HashMap<String, Object>> data = new ArrayList<HashMap<String, Object>>();for (Person person : persons) {HashMap<String, Object> item = new HashMap<String, Object>();item.put("name", person.getName());item.put("phone", person.getPhone());item.put("id", person.getId());data.add(item);}/** * 设置好适配器对应的关系 */SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.item,new String[] { "name", "phone" }, new int[] { R.id.name,R.id.phone });listView.setAdapter(adapter);}}
自定义的Adapter
package cn.roco.db.adapter;import java.util.List;import cn.roco.db.R;import cn.roco.db.domain.Person;import android.content.Context;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.TextView;public class PersonAdapter extends BaseAdapter {private List<Person> persons; //绑定数据private int resouce ; //绑定的条目节目private LayoutInflater inflater;public PersonAdapter(Context context, List<Person> persons,int resouce) {this.persons=persons;this.resouce=resouce;inflater= (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);}@Override//得到总的数量public int getCount() {return persons.size(); //数据总数}@Override//根据ListView位置返回Viewpublic Object getItem(int position) {return persons.get(position);}@Override //根据ListView位置得到List中的IDpublic long getItemId(int position) {return position;}@Override //根据位置得到View对象public View getView(int position, View convertView, ViewGroup parent) {TextView nameView=null;TextView phoneView=null;if (convertView==null) {convertView=inflater.inflate(resouce, null);//生成条目节目对象 //得到条目中的子组件nameView=(TextView) convertView.findViewById(R.id.name);phoneView= (TextView) convertView.findViewById(R.id.phone);ViewCache cache=new ViewCache();cache.nameView=nameView;cache.phoneView=phoneView;convertView.setTag(cache);}else{ViewCache cache=(ViewCache) convertView.getTag();nameView=cache.nameView;phoneView=cache.phoneView;}//从list对象中为子组件赋值 实现数据绑定Person person= persons.get(position);nameView.setText(person.getName());phoneView.setText(person.getPhone());return convertView;}/** * 定义的缓存类 */private final class ViewCache{public TextView nameView;public TextView phoneView;}}