android 以编程的方式使用SQLite数据库 执行CRUD（创建 读取 更新 删除）操作

DBAdapter数据库辅助类

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;  
    }  
}  

DatabaseActivity

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", "[email protected]");  
        dbAdapter.insertContact("Jackson", "[email protected]");  
          
    }  
  
  
}