android之SQLite

package com.example.sql;

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.graphics.Color;
import android.view.Menu;
import android.widget.TextView;

public class MainActivity extends Activity {

	private TextView tv;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		DBHelper db=new DBHelper(this);
		tv=(TextView)findViewById(R.id.tv);
		tv.setBackgroundColor(Color.RED);
		db.clear();
		//db.insert();
		//String str=db.query(0);
		//System.out.println(str);
		//db.insert();
		db.insert1(3,"cmaker");
		String str=db.query(0);
		tv.setText(str);
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}
}
class DBHelper extends SQLiteOpenHelper
{
	private static final String CREATE_TABLE_SQL="create table TempTb1(_id integer,name text)";
	private SQLiteDatabase db;
	DBHelper(Context context)
	{
		super(context,"test.db",null,2);
	}
	@Override
	public void onCreate(SQLiteDatabase db)
	{
		db.execSQL(CREATE_TABLE_SQL);
	}
	@Override
	public void onUpgrade(SQLiteDatabase db,int OldVersion,int NewVersion)
	{
	}
	public void insert()
	{
		String sql="insert into TempTb1(_id,name)values(1,'amaker')";
		getWritableDatabase().execSQL(sql);
	}
	public void insert1(int id,String name)
	{
		//String sql="insert into TempTb1(_id,name)values(2,'bmaker')";
		//getWritableDatabase().execSQL(sql);
		getWritableDatabase().execSQL("insert into TempTb1(_id,name)values(?,?)",new Object[]{id,name});
	}
	public String query(int index)
	{
		SQLiteDatabase db=this.getWritableDatabase();
		Cursor cur=db.query("TempTb1",null,null,null,null,null,null);
		if(cur.moveToFirst())//note
		{
			cur.move(index);
			int id=cur.getInt(0);
			String name=cur.getString(1);
			String str=id+":"+name;
			//System.out.println(id+":"+name);
			db.close();//note
			return str;
		}
		return "Fail to find any item";
	}
	public void clear()
	{
		SQLiteDatabase db=this.getWritableDatabase();
		db.execSQL("delete from TempTb1");
	}
}