Android系统集成了一个轻量级的数据库SQLite，是一个嵌入式的数据库引擎，适用于资源有限的设备适量数据存取

Android提供了SQLiteOpenHelper类，作为访问SQLite的助手类，通常都会继承SQLiteOpenHelper开发子类

SQLiteOpenHelper类提供两个方面的功能：

第一，getReadableDatabase(),getWritableDatabase()可以获得SQLiteDatabse对象，通过该对象可以对数据库进行操作

第二，提供了onCreate()和onUpgrade()两个回调函数，允许我们在创建和升级数据库时，进行自己的操作

例程：

DatabaseHelper.java

import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper; public class DatabaseHelper extends SQLiteOpenHelper { private static final int VERSION = 1; //在SQLiteOepnHelper的子类当中，必须有该构造函数 public DatabaseHelper(Context context, String name, CursorFactory factory, int version) { //必须通过super调用父类当中的构造函数 super(context, name, factory, version); // TODO Auto-generated constructor stub } public DatabaseHelper(Context context, String name) { this(context, name, VERSION); // TODO Auto-generated constructor stub } public DatabaseHelper(Context context,String name,int version){ this(context,name,null,version); } @Override public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub System.out.println("create a Database"); //execSQL函数用于执行SQL语句，创建一个表名为user,有两列数据id、name db.execSQL("create table user(id int,name varchar(20))"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub System.out.println("update a Database"); } } 主要Activity

SQLiteActivity.java(五个按钮：创建数据库、更新数据库版本、插入数据、更新数据、查询数据、删除数据)

import android.app.Activity; import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import com.mars.sqlite.db.DatabaseHelper; public class SQLiteActivity extends Activity { private Button createButton; private Button updateButton; private Button insertButton; private Button updateRecordButton; private Button queryButton; private Button deleteButton; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); createButton = (Button)findViewById(R.id.createDatabase); updateButton = (Button)findViewById(R.id.updateDatabase); insertButton = (Button)findViewById(R.id.insert); updateRecordButton = (Button)findViewById(R.id.update); queryButton = (Button)findViewById(R.id.query); deleteButton = (Button)findViewById(R.id.delete); createButton.setOnClickListener(new CreateListener()); updateButton.setOnClickListener(new UpdateListener()); insertButton.setOnClickListener(new InsertListener()); updateRecordButton.setOnClickListener(new UpdateRecordListener()); queryButton.setOnClickListener(new QueryListener()); deleteButton.setOnClickListener(new DeleteListener()); } class CreateListener implements OnClickListener{ public void onClick(View v){ DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this, "test_db"); //只有调用了DatabaseHelper对象的getReadableDatabase()方法，或者是getWritableDatabase()方法之后，才会创建，或打开一个数据库 SQLiteDatabase db = dbHelper.getReadableDatabase(); } } class UpdateListener implements OnClickListener{ @Override public void onClick(View v) { DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this, "test_db",2); SQLiteDatabase db = dbHelper.getReadableDatabase(); } } //insert into <表名>（key1,key2,..） values（value1，value2） where class InsertListener implements OnClickListener{ @Override public void onClick(View v) { ContentValues values = new ContentValues(); values.put("id",1); values.put("name","wanger"); DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this, "test_db",2); SQLiteDatabase db = dbHelper.getWritableDatabase(); db.insert("user", null, values); } } //updata table_name set XXCOL=XXX where XXCOL=XX... class UpdateRecordListener implements OnClickListener{ @Override public void onClick(View v) { DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this, "test_db",2); SQLiteDatabase db = dbHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("name", "wangerniang"); db.update("user",values,"id = ?",new String[]{"1"}); } } class QueryListener implements OnClickListener{ @Override public void onClick(View v) { DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_db",2); SQLiteDatabase db = dbHelper.getReadableDatabase(); Cursor cursor = db.query("user", new String[]{"id","name"}, "id=http://www.it165.net/database/html/201412/?", new String[]{"1"}, null, null, null); while(cursor.moveToNext()){ String name = cursor.getString(cursor.getColumnIndex("name")); System.out.println("query--->" + name); } } } //delete <table> where <whereClause> class DeleteListener implements OnClickListener{ @Override public void onClick(View v) { // TODO Auto-generated method stub DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_db",2); SQLiteDatabase db = dbHelper.getWritableDatabase(); db.delete("user", "name = ?",new String[]{"wanger"} ); } } }

备注:

当更新数据库的版本为2时，后面增改查删操作之前打开数据库就要用版本为2，

如果选择默认（默认版本为1），会报错（不能从版本2降级到版本1）