SQLieOpenHelper
getReadableDatabase(),getwritableDatabase();
SQLiteDatabase提供一系列管理数据库的方法。
OnCreate(SQLiteDatabase db),OnOpen(SQLiteDatabase db),
Onupgrade(SQLiteDatabase db,int old Version,int newVersion);
close();
adb对数据库的几个简单命令
adb shell
#sqlite3 数据库名
sqlite>.schema 当前数据库中的表
sqlite>select * from 数据库名
DatabaseHelper.java
//DatabaseHelper作为一个访问SQLite的助手类,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
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,VERSION); } public DatabaseHelper(Context context,int version){ this(context,null,version); }
//该函数是在第一次创建数据库的时候执行,实际上是在第一次得到SQLiteDatabse对象的时候,才会调用这个方法 @Override public voidonCreate(SQLiteDatabase db) { // TODO Auto-generated method stub System.out.println("create a Database"); //execSQL函数用于执行SQL语句 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"); }
}
SQLiteActiviey.java
import mars.sqlite3.db.DatabaseHelper;
public class SQLiteActivity extends Activity { /** Called when the activity is first created. */ private Button createButton; private Button insertButton; private Button updateButton; private Button updateRecordButton; private Button queryButton; @Override public 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); createButton.setOnClickListener(new CreateListener()); updateButton.setOnClickListener(new UpdateListener()); insertButton.setOnClickListener(new InsertListener()); updateRecordButton.setOnClickListener(new UpdateRecordListener()); queryButton.setOnClickListener(new QueryListener()); } class CreateListener implements OnClickListener{ @Override public void onClick(View v) { //创建一个DatabaseHelper对象 DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_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_mars_db",2); SQLiteDatabase db = dbHelper.getReadableDatabase(); } } class InsertListener implements OnClickListener{
@Override public void onClick(View v) { //生成ContentValues对象 ContentValues values = new ContentValues(); //想该对象当中插入键值对,其中键是列名,值是希望插入到这一列的值,值必须和数据库当中的数据类型一致 values.put("id",1); values.put("name","zhangsan"); DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,2); SQLiteDatabase db = dbHelper.getWritableDatabase(); //调用insert方法,就可以将数据插入到数据库当中 db.insert("user",values); } } //更新操作就相当于执行SQL语句当中的update语句 //UPDATE table_name SET XXCOL=XXX WHERE XXCOL=XX... class UpdateRecordListener implements OnClickListener{
@Override public void onClick(View arg0) { // TODO Auto-generated method stub //得到一个可写的SQLiteDatabase对象 DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db"); SQLiteDatabase db = dbHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("name","zhangsanfeng"); //第一个参数是要更新的表名 //第二个参数是一个ContentValeus对象 //第三个参数是where子句 db.update("user",values,"id=?",new String[]{"1"}); } } class QueryListener implements OnClickListener{
@Override public void onClick(View v) { System.out.println("aaa------------------"); Log.d("myDebug","myFirstDebugMsg"); DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db"); SQLiteDatabase db = dbHelper.getReadableDatabase(); Cursor cursor = db.query("user",new String[]{"id","name"},new String[]{"1"},null); while(cursor.moveToNext()){ String name = cursor.getString(cursor.getColumnIndex("name")); System.out.println("query--->" + name); } } } } (编辑:李大同)
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