package com.databses;    import android.content.ContentValues;  import android.content.Context;  import android.database.Cursor;  import android.database.SQLException;  import android.database.sqlite.SQLiteDatabase;  import android.database.sqlite.SQLiteOpenHelper;  import android.util.Log;    public class DBAdapter {        static final String KEY_ROWID = "_id";      static final String KEY_NAME = "name";      static final String KEY_EMAIL = "email";      static final String TAG = "DBAdapter";            static final String DATABASE_NAME = "mydb";      static final String DATABASE_TABLE = "contacts";      static final int DATABASE_VERSION = 1;      final Context context;            //创建表sql语句      static final String DATABASE_CREATE = "create table contacts (_id integer primary key autoincrement,name text not null,email text not null)";            SQLiteDatabase db;      DatabaseHelper dBHelper;            public DBAdapter(Context context){          this.context = context;          dBHelper = new DatabaseHelper(context);      }            //数据库辅助类 继承SQLiteOpenHelper      private static class DatabaseHelper extends SQLiteOpenHelper{          public DatabaseHelper(Context context) {              super(context, DATABASE_NAME, null, DATABASE_VERSION);          }            //创建数据库          @Override          public void onCreate(SQLiteDatabase db) {              try {                  db.execSQL(DATABASE_CREATE);              } catch (Exception e) {                  e.printStackTrace();              }          }          //升级数据库版本          @Override          public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {              Log.w(TAG, "upgrading db from version "+oldVersion+"to"+newVersion+",which will destory all old data");              db.execSQL("drop table if exists contacts");              onCreate(db);          }      }            //打开数据库      public DBAdapter open() throws SQLException      {          db = dBHelper.getWritableDatabase();          return this;      }            //关闭数据库      public void close(){          dBHelper.close();      }            //插入一条联系人记录      public long insertContact(String name,String email){          ContentValues initalValues = new ContentValues();          initalValues.put(KEY_NAME,name);          initalValues.put(KEY_EMAIL, email);          return db.insert(DATABASE_TABLE, null, initalValues);      }            //删除一条记录      public boolean deleteContact(long rowId){          return db.delete(DATABASE_TABLE,KEY_ROWID+"="+rowId,null)>0;      }            //查询所有联系人      public Cursor getAllContacts()      {          return db.query(DATABASE_TABLE, new String[]{KEY_ROWID,KEY_NAME,KEY_EMAIL},null, null, null, null, null, null);      }            //查询一条记录      public Cursor getContact(long rowId) throws SQLException{          Cursor cursor = db.query(true, DATABASE_TABLE, new String[]{KEY_ROWID,KEY_NAME,KEY_EMAIL}, KEY_ROWID+"="+rowId, null, null, null, null, null);          if(cursor != null){              cursor.moveToFirst();          }          return cursor;      }            //更新一个联系人      public boolean updateContact(long rowId,String name,String email){          ContentValues contentValues = new ContentValues();          contentValues.put(KEY_NAME, name);          contentValues.put(KEY_EMAIL, email);          return db.update(DATABASE_TABLE, contentValues, KEY_ROWID+"="+KEY_ROWID, null)>0;      }  }  

package com.databses;    import android.os.Bundle;  import android.app.Activity;  import android.view.Menu;    public class DatabasesActivity extends Activity {        @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_databases);          DBAdapter dbAdapter = new DBAdapter(this);                    dbAdapter.open();          dbAdapter.insertContact("weiwei", "weiwei@163.com");          dbAdapter.insertContact("Jackson", "Jackson@163.com");                }      }