android 数据库操作
另一篇：http://database.51cto.com/art/200903/113334.htm
public class DatabaseHelper extends SQLiteOpenHelper {
private final static String NAME="sharp.db";
//Factory:代表记录集游标工厂，是专门用来生成记录集游标，记录集游标是对查询结果进行迭代的，后面我们会继续介绍。
public DatabaseHelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}
public DatabaseHelper(Context context){
super(context, NAME, null, 1);
}
/**
* 用户第一次使用软件时调用，实现数据库的操作crud
*/
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
Log.i("save", "create");
db.execSQL("create table person(personid integer primary key autoincrement,name varcahr(20),age integer)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("drop table if exists person");
onCreate(db);
}
/**
* 根据版本号进行更新
* @param db
* @param mNewVersion
*/
public void checkVersionCreate(SQLiteDatabase db,int mNewVersion){
int version = db.getVersion();
if (version != mNewVersion) {
db.beginTransaction();
try {
if (version == 0) {
onCreate(db);
}else{
onUpgrade(db, version,mNewVersion);
}
db.setVersion(mNewVersion); //设置为新的版本号
db.setTransactionSuccessful();
}
finally{
db.endTransaction();
}
}
}
/**
* 数据库名不空，获得数据库实例
* @param mDatabase
* @param mContext
* @param mName
* @param mFactory
* @return
*/
public SQLiteDatabase getDatabase(SQLiteDatabase mDatabase,Context mContext,String mName,CursorFactory mFactory){
if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) {
return mDatabase; // The database is already open for business
}
if (mName == null) {
mDatabase = SQLiteDatabase.create(null);
} else {
mDatabase = mContext.openOrCreateDatabase(mName, 0, mFactory);
}
return mDatabase;
}
}
DbService：
public class DbService {
private DatabaseHelper databaseHelper;
private Context context;
public DbService(Context context){
this.context=context;
databaseHelper=new DatabaseHelper(this.context);
}
//保存
public void save(Person person){
SQLiteDatabase db = databaseHelper.getWritableDatabase();
db.execSQL("insert into person(name, age) values(?,?)",new Object[]{person.getName(), person.getAge()});
}
//更新
public void update(Person person){
SQLiteDatabase db = databaseHelper.getWritableDatabase();
db.execSQL("update person set name=?,age=? where personid=?",
new Object[]{person.getName(), person.getAge(),
person.getId()});
}
//根据id查找
public Person find(Integer id){
SQLiteDatabase db = databaseHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select personid,name,age from person where personid=?", new String[]{String.valueOf(id)});
if(cursor.moveToNext()){ //迭代记录集
Person person = new Person();//实例化person
person.setId(cursor.getInt(cursor.getColumnIndex("personid")));
person.setName(cursor.getString(1));
person.setAge(cursor.getInt(2)); //将查到的字段，放入person，
return person;
}
cursor.close();//游标关闭
return null;
}
//删除
public void delete(Integer id){
SQLiteDatabase db=databaseHelper.getWritableDatabase();
db.execSQL("delete from person where id=?",new Object[]{id});
}
//
public List<Person> getScrollData(int firstResult, int maxResult){
List<Person> persons = new ArrayList<Person>();
SQLiteDatabase db = databaseHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select personid,name,age from person limit ?,?",
new String[]{String.valueOf(firstResult),String.valueOf(maxResult)}); //firstResult开始索引
while(cursor.moveToNext()){ //maxResult每页获取的记录数
Person person = new Person();
person.setId(cursor.getInt(cursor.getColumnIndex("personid")));
person.setName(cursor.getString(1));
person.setAge(cursor.getInt(2));
persons.add(person);
}
cursor.close();
return persons;
}
//
public long getCount(){
SQLiteDatabase db = databaseHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select count(*) from person", null);
//没有占位符参数的话，直接用null
cursor.moveToFirst();
long count = cursor.getLong(0);
cursor.close();
return count;
}
//
public void close(){
databaseHelper.close();
}
}
Person：
public class Person {
private Integer id;
private String name;
private Integer age;
public Person(){}
public Person(String name,Integer age){
this.name=name;
this.age=age;
}
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 Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "Person [age=" + age + ", id=" + id + ", name=" + name + "]";
}
}
PersonServiceTest：
public class PersonServiceTest extends AndroidTestCase{
public void testSave() throws Throwable{ //测试保存方法
DbService personService = new DbService(this.getContext());
//传入上下文
Person person = new Person("Tom", 21);
personService.save(person);
}
}
一个activity：
public class SqlLiteActivity extends Activity {
/** Called when the activity is first created. */
private final static String TAG="PersonActivity";
private ListView listView;
private DbService personService;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
listView = (ListView)findViewById(R.id.personList);
personService = new DbService(this);
save(personService);
List<Person> persons = personService.getScrollData(0, 3);//前十条数据
List<HashMap<String, String>> data = new
ArrayList<HashMap<String,String>>();
HashMap<String, String>title = new HashMap<String, String>();
title.put("personid","编号");
title.put("name", "姓名");
title.put("age", "年龄");
data.add(title); //标题
for(Person person : persons){
HashMap<String, String> map = new HashMap<String, String>();
map.put("personid", String.valueOf(person.getId()));
map.put("name", person.getName());
map.put("age", String.valueOf(person.getAge()));
data.add(map); //显示各个数据
}
SimpleAdapter adapter = new SimpleAdapter(SqlLiteActivity.this,
data, R.layout.personitem, new String[]{"personid", "name","age"},
new int[]{R.id.personid, R.id.name, R.id.age});
listView.setAdapter(adapter);
}
//
public void save(DbService service){
for(int i=0;i<5;i++){
Person person=new Person();
person.setName("d");
person.setAge(12);
service.save(person);
}
}
} main.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 android:id="@+id/personList" android:layout_width="fill_parent" android:layout_height="wrap_content" ></ListView> </LinearLayout>
personitem.xml<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TextView
android:layout_width="60px"
android:layout_height="wrap_content"
android:id="@+id/personid"
/>
<TextView
android:layout_width="160px"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/personid"
android:layout_alignTop="@id/personid"
android:gravity="center_horizontal"
android:id="@+id/name"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/name"
android:layout_alignTop="@id/name"
android:id="@+id/age"
/>
</RelativeLayout>