android在sd卡建库时为啥我建库一点反映都没有，没有生成的文件。【贴的是java文件】

Question

package com.example.test13;

import android.app.Activity;

import android.content.ContentValues;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.os.Bundle;

import android.support.v4.app.Fragment;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.Toast;

public class DBActivity extends Activity{

public static class PlaceholderFragment extends Fragment {

       public PlaceholderFragment() {

       }

       @Override

       public View onCreateView(LayoutInflater inflater, ViewGroup container,

               Bundle savedInstanceState) {

           View rootView = inflater.inflate(R.layout.fragment_main, container, false);

           return rootView;

       }

   }

protected void onCreat(Bundle savedInstanceState){

super.onCreate(savedInstanceState);

setContentView(R.layout.fragment_main);

String sname="chengkaige";

String sid="2014011797";

Button b1=(Button)this.findViewById(R.id.butCreateDB);

b1.setOnClickListener(new OnClickListener(){

public void onClick(View v)

{

SQLiteDatabase db =SQLiteDatabase.openOrCreateDatabase("/scard/abc.db",null);

}});

//建库

Button b2=(Button)this.findViewById(R.id.button1);

b2.setOnClickListener(new OnClickListener(){

public void onClick(View v)

{

SQLiteDatabase db =SQLiteDatabase.openOrCreateDatabase("/scard/abc.db",null);

String sql ="create table books(id VARCHAR(30) NOT NULL,price float";

db.execSQL(sql);

}});

//建表，而且table里面一个库只能创建一次。

Button b3=(Button)this.findViewById(R.id.button2);

b3.setOnClickListener(new OnClickListener(){

public void onClick(View v)

{

SQLiteDatabase db =SQLiteDatabase.openOrCreateDatabase("/scard/abc.db",null);

String sname="chengkaige";

String sid="2014011797";

ContentValues newValues = new ContentValues();

newValues.put("id", sid);

newValues.put("name", sname);

newValues.put("price", 100);

db.insert("books",null,newValues);

}});

//插入

Button b4=(Button)this.findViewById(R.id.button3);

b4.setOnClickListener(new OnClickListener(){

public void onClick(View v)

{

SQLiteDatabase db =SQLiteDatabase.openOrCreateDatabase("/scard/abc.db",null);

   db.delete("books", null, null);

}});

//删除,delete不返回，books加双引号，因为是字符串。

Button b5=(Button)this.findViewById(R.id.button4);

b5.setOnClickListener(new OnClickListener(){

public void onClick(View v)

{

SQLiteDatabase db =SQLiteDatabase.openOrCreateDatabase("/scard/abc.db",null);

ContentValues updateValues = new ContentValues();

updateValues.put("name","sname");

updateValues.put("id", "sid");

}});

//更新功能。

Button b6=(Button)this.findViewById(R.id.button5);

b6.setOnClickListener(new OnClickListener(){

public void onClick(View v)

{

String sname="chengkaige";

String sid="2014011797";

SQLiteDatabase db =SQLiteDatabase.openOrCreateDatabase("/scard/abc.db",null); 

Cursor m_cursor = db.query("books", null,"id='"+sid+"'", null, null, null, null);

String strRes="";

while(m_cursor.moveToNext()){

String str1=m_cursor.getString(1);

strRes=strRes+str1+"==";

}

Toast.makeText(DBActivity.this, strRes, Toast.LENGTH_LONG);

}});

//查询功能。

}

   

}