Android（三）数据存储之三SQLite嵌入式数据库 2

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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<Contact> 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<Contact> contacts = new ArrayList<Contact>();                    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<Contact> 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：<uses-library android:name="android.test.runner"/>，为application元素添加一个兄弟元素：<instrumentation android:name="android.test.InstrumentationTestRunner"     android:targetPackage="com.changcheng.sqlite" android:label="Tests for My App" />。
 
       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：

<?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">          <!-- ListView -->          <ListView android:layout_width="fill_parent"                    android:layout_height="fill_parent" android:id="@+id/listView" />   </LinearLayout>