android中操作SQLite注意事项

1. 调用rawQuery()后，需要调用Cursor的movToFirst();

public Cursor query(String sql, String[] args){
		SQLiteDatabase db = this.getReadableDatabase();
		Cursor cursor = db.rawQuery(sql, args);
		cursor.moveToFirst();  // 重中之重，千万不能忘了
		db.close();
		return cursor;
	}

2.删除记录时使用 sql ="delete from student where id = ?"

sql ="delete from student where id = ?";
server.delete(sql, new Object[]{113});

public void delete(String sql, Object[] args){
		SQLiteDatabase db = this.getReadableDatabase();
		db.execSQL(sql, args);
		this.sql = sql;
		db.close();
	}

MainActivity.class

package com.example.db1;

import java.util.Random;

import android.R.string;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import android.widget.Toast;

public class DbServer extends SQLiteOpenHelper {
	private final static int DatabaseVersion = 1;
	private final static String DatabaseName = "abcd.db";
	public static int cnt = 111;
	public static String sql = null;
	
	public DbServer(Context context) {
		super(context, DatabaseName, null, DatabaseVersion);
		// TODO Auto-generated constructor stub
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		MainActivity.cnt = 1;
		this.cnt = 101;
		// TODO Auto-generated method stub
		String sql = "CREATE TABLE student (id INT PRIMARY KEY, NAME VARCHAR(10))";
		db.execSQL(sql);
		db.close();
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// TODO Auto-generated method stub
		  
	}

	public Cursor query(String sql, String[] args){
		SQLiteDatabase db = this.getReadableDatabase();
		Cursor cursor = db.rawQuery(sql, args);
		cursor.moveToFirst();  // 重中之重，千万不能忘了
		db.close();
		return cursor;
	}
	
	public void insert(String sql, Object[] args){
		SQLiteDatabase db = this.getReadableDatabase();
		this.sql = sql;
		db.execSQL(sql,args);
		db.close();
	}
	
	public void update(String sql, Object[] args){
		SQLiteDatabase db = this.getReadableDatabase();
		this.sql = sql;
		db.execSQL(sql,args);
		db.close();
	}
	
	public void delete(String sql, Object[] args){
		SQLiteDatabase db = this.getReadableDatabase();
		db.execSQL(sql, args);
		this.sql = sql;
		db.close();
	}
}

SQLiteOpenHelper的子类

package com.example.db1;

import java.util.Random;

import android.R.string;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import android.widget.Toast;

public class DbServer extends SQLiteOpenHelper {
	private final static int DatabaseVersion = 1;
	private final static String DatabaseName = "abcd.db";
	public static int cnt = 111;
	public static String sql = null;
	
	public DbServer(Context context) {
		super(context, DatabaseName, null, DatabaseVersion);
		// TODO Auto-generated constructor stub
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		MainActivity.cnt = 1;
		this.cnt = 101;
		// TODO Auto-generated method stub
		String sql = "CREATE TABLE student (id INT PRIMARY KEY, NAME VARCHAR(10))";
		db.execSQL(sql);
		db.close();
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// TODO Auto-generated method stub
		  
	}

	public Cursor query(String sql, String[] args){
		SQLiteDatabase db = this.getReadableDatabase();
		Cursor cursor = db.rawQuery(sql, args);
		cursor.moveToFirst();  // 重中之重，千万不能忘了
		db.close();
		return cursor;
	}
	
	public void insert(String sql, Object[] args){
		SQLiteDatabase db = this.getReadableDatabase();
		this.sql = sql;
		db.execSQL(sql,args);
		db.close();
	}
	
	public void update(String sql, Object[] args){
		SQLiteDatabase db = this.getReadableDatabase();
		this.sql = sql;
		db.execSQL(sql,args);
		db.close();
	}
	
	public void delete(String sql, Object[] args){
		SQLiteDatabase db = this.getReadableDatabase();
		db.execSQL(sql, args);
		this.sql = sql;
		db.close();
	}
}