Android（三）数据存储之三SQLite嵌入式数据库
}
}
3.编写MyOpenHelper类
MyOpenHelper继承自SQLiteOpenHelper类。我们需要创建数据表，必须重写onCreate（更新时重写onUpgrade方法）方法，在这个方法中创建数据表。
package com.changcheng.sqlite;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class MyOpenHelper extends SQLiteOpenHelper {
private static final String name = "contants"; // 数据库名称
private static final int version = 1; // 数据库版本
public MyOpenHelper(Context context) {
/**
* CursorFactory指定在执行查询时获得一个游标实例的工厂类。 设置为null，则使用系统默认的工厂类。
*/
super(context, name, null, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
// 创建contacts表，SQL表达式时提供的字段类型和长度仅为提高代码的可读性。
db.execSQL("CREATE TABLE IF NOT EXISTS contacts("
+ "_id integer primary key autoincrement,"
+ "name varchar(20)," + "phone varchar(50))");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// 仅演示用，所以先删除表然后再创建。
db.execSQL("DROP TABLE IF EXISTS contacts");
this.onCreate(db);
}
}
4.编写ContactsService类
ContactsService类主要实现对业务逻辑和数据库的操作。
package com.changcheng.sqlite.service;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.database.Cursor;
import com.changcheng.sqlite.MyOpenHelper;
import com.changcheng.sqlite.entity.Contact;
public class ContactsService {
private MyOpenHelper openHelper;
public ContactsService(Context context) {
this.openHelper = new MyOpenHelper(context);
}
/**
* 保存
*
* @param contact
*/
public void save(Contact contact) {
String sql = "INSERT INTO contacts (name, phone) VALUES (?, ?)";
Object[] bindArgs = { contact.getName(), contact.getPhone() };
this.openHelper.getWritableDatabase().execSQL(sql, bindArgs);
}
/**
* 查找
*
* @param id
* @return
*/
public Contact find(Integer id) {
String sql = "SELECT _id,name, phone FROM contacts WHERE _id=?";
String[] selectionArgs = { id + "" };
Cursor cursor = this.openHelper.getReadableDatabase().rawQuery(sql,
selectionArgs);
if (cursor.moveToFirst())
return new Contact(cursor.getInt(0), cursor.getString(1), cursor
.getString(2));
return null;
}
/**
* 更新
*
* @param contact
*/
public void update(Contact contact) {
String sql = "UPDATE contacts SET name=?, phone=? WHERE _id=?";
Object[] bindArgs = { contact.getName(), contact.getPhone(),
contact.get_id() };
this.openHelper.getWritableDatabase().execSQL(sql, bindArgs);
}
/**
* 删除
*
* @param id
*/
public void delete(Integer id) {
String sql = "DELETE FROM contacts WHERE _id=?";
Object[] bindArgs = { id };
this.openHelper.getReadableDatabase().execSQL(sql, bindArgs);
}
/**
* 获取记录数量
*
* @return
*/
public long getCount() {
String sql = "SELECT count(*) FROM contacts";
Cursor cursor = this.openHelper.getReadableDatabase().rawQuery(sql,
null);
cursor.moveToFirst();
return cursor.getLong(0);
}
/**
* 获取分页数据
*
* @param startIndex
* @param maxCount
* @return
*/
public List getScrollData(long startIndex, long maxCount) {
String sql = "SELECT _id,name,phone FROM contacts LIMIT ?,?";
String[] selectionArgs = { String.valueOf(startIndex),
String.valueOf(maxCount) };
Cursor cursor = this.openHelper.getReadableDatabase().rawQuery(sql,
selectionArgs);
List contacts = new ArrayList();
while (cursor.moveToNext()) {
Contact contact = new Contact(cursor.getInt(0),
cursor.getString(1), cursor.getString(2));
contacts.add(contact);
}
return contacts;
}
/**
* 获取分页数据，提供给SimpleCursorAdapter使用。
*
* @param startIndex
* @param maxCount
* @return
*/
public Cursor getScrollDataCursor(long startIndex, long maxCount) {
String sql = "SELECT _id,name,phone FROM contacts LIMIT ?,?";
String[] selectionArgs = { String.valueOf(startIndex),
String.valueOf(maxCount) };
Cursor cursor = this.openHelper.getReadableDatabase().rawQuery(sql,
selectionArgs);
return cursor;
}
}
5.编写测试类
编写一个针对ContactsService的测试类，测试ContactsService类中的各个方法是否正确。
package com.changcheng.sqlite.test;
import java.util.List;
import com.changcheng.sqlite.MyOpenHelper;
import com.changcheng.sqlite.entity.Contact;
import com.changcheng.sqlite.service.ContactsService;
import android.database.Cursor;
import android.test.AndroidTestCase;
import android.util.Log;
public class ContactsServiceTest extends AndroidTestCase {
private static final String TAG = "ContactsServiceTest";
// 测试创建表
public void testCreateTable() throws Throwable {
MyOpenHelper openHelper = new MyOpenHelper(this.getContext());
openHelper.getWritableDatabase();
}
// 测试save
public void testSave() throws Throwable {
ContactsService contactsService = new ContactsService(this.getContext());
Contact contact1 = new Contact(null, "tom", "13898679876");
Contact contact2 = new Contact(null, "lili", "13041094909");
Contact contact3 = new Contact(null, "jack", "13504258899");
Contact contact4 = new Contact(null, "heary", "1335789789");
contactsService.save(contact1);
contactsService.save(contact2);
contactsService.save(contact3);
contactsService.save(contact4);
}
// 测试find
public void testFind() throws Throwable {
ContactsService contactsService = new ContactsService(this.getContext());
Contact contact = contactsService.find(1);
Log.i(TAG, contact.toString());
}
// 测试update
public void testUpdate() throws Throwable {
ContactsService contactsService = new ContactsService(this.getContext());
Contact contact = contactsService.find(1);
contact.setPhone("1399889955");
contactsService.update(contact);
}
// 测试getCount
public void testGetCount() throws Throwable {
ContactsService contactsService = new ContactsService(this.getContext());
Log.i(TAG, contactsService.getCount() + "");
}
// 测试getScrollData
public void testGetScrollData() throws Throwable {
ContactsService contactsService = new ContactsService(this.getContext());
List contacts = contactsService.getScrollData(0, 3);
Log.i(TAG, contacts.toString());
}
// 测试getScrollDataCursor
public void testGetScrollDataCursor() throws Throwable {
ContactsService contactsService = new ContactsService(this.getContext());
Cursor cursor = contactsService.getScrollDataCursor(0, 3);
while (cursor.moveToNext()) {
Contact contact = new Contact(cursor.getInt(0),
cursor.getString(1), cursor.getString(2));
Log.i(TAG, contact.toString());
}
}
}
启用测试功能，不要忘记在AndroidManifest.xml文件中加入测试环境。为application元素添加一个子元素：，为application元素添加一个兄弟元素：。
SQLite数据库以单个文件存储，就像微软的Access数据库。有一个查看SQLite数据库文件的工具——SQLite Developer，我们可以使用它来查看数据库。Android将创建的数据库存放在”/data/data/ com.changcheng.sqlite/databases/contacts”，我们将它导出然后使用SQLite Developer打开。
6.分页显示数据
我们在ContactsService类中，提供了一个获取分页数据的方法。我们将调用它获取的数据，使用ListView组件显示出来。
编辑mail.xml：
"1.0" encoding="utf-8"?>
"http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent">
<!-- ListView -->
"fill_parent"
android:layout_height="fill_parent" android:id="@+id/listView" />
在mail.xml所在目录里添加一个contactitem.xml：
"1.0" encoding="utf-8"?>
"http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content" android:layout_height="wrap_content">
<!-- contact.id -->
"30dip" android:layout_height="wrap_content"
android:textSize="20sp" android:id="@+id/tv_id" />
<!-- contact.name -->
"150dip" android:layout_height="wrap_content"
android:textSize="20sp" android:layout_toRightOf="@id/tv_id"
android:layout_alignTop="@id/tv_id" android:id="@+id/tv_name" />
<!-- contact.phone -->
"150dip" android:layout_height="wrap_content"
android:textSize="20sp" android:layout_toRightOf="@id/tv_name"
android:layout_alignTop="@id/tv_name" android:id="@+id/tv_phone" />
编辑AndroidSQLite类：
package com.changcheng.sqlite;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import com.changcheng.sqlite.R;
import com.changcheng.sqlite.entity.Contact;
import com.changcheng.sqlite.service.ContactsService;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;
public class AndroidSQLite extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// 获取分页数据
ContactsService contactsService = new ContactsService(this);
List contacts = contactsService.getScrollData(0, 3);
// 获取ListView
ListView lv = (ListView) this.findViewById(R.id.listView);
// 生成List>数据
List> data = new ArrayList>();
for (Contact contact : contacts) {
HashMap item = new HashMap();
item.put("_id", contact.get_id());
item.put("name", contact.getName());
item.put("phone", contact.getPhone());
data.add(item);
}
// 生成Adapter
SimpleAdapter adapter = new SimpleAdapter(this, data,
R.layout.contactitem, new String[] { "_id", "name", "phone" },
new int[] { R.id.tv_id, R.id.tv_name, R.id.tv_phone });
// 设置ListView适配器
lv.setAdapter(adapter);
// 为ListView添加事件
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView parent, View view,
int position, long id) {
HashMap item = (HashMap) parent
.getItemAtPosition((int) id);
Toast.makeText(AndroidSQLite.this, item.get("name").toString(),
1).show();
}
});
}
}
上面编写的分页显示数据比较麻烦，Android为我们提供了一个SimpleCursorAdapter类。使用它可以方便的显示分页数据。将AndroidSQLite类修改为：
package com.changcheng.sqlite;
import com.changcheng.sqlite.R;
import com.changcheng.sqlite.service.ContactsService;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class AndroidSQLite extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// 获取分页数据
ContactsService contactsService = new ContactsService(this);
Cursor cursor = contactsService.getScrollDataCursor(0, 3);
// 获取ListView
ListView lv = (ListView) this.findViewById(R.id.listView);
// 创建Adapter
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
R.layout.contactitem, cursor, new String[] { "_id", "name",
"phone" }, new int[] { R.id.tv_id, R.id.tv_name,
R.id.tv_phone });
// 设置ListView适配器
lv.setAdapter(adapter);
// 为ListView添加事件
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView parent, View view,
int position, long id) {
Cursor cursor = (Cursor) parent
.getItemAtPosition((int) position);
Toast.makeText(AndroidSQLite.this, cursor.getString(1), 1)
.show();
}
});
}
}
OK，在Android中的SQLite操作总结结束！
