使用android studio编写一个简单的使用sqlite存储数据的程序，数据一直保存不了

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <Button
        android:id="@+id/create_database"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Create database"/>
    <Button
        android:id="@+id/add_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Add data"/>
</LinearLayout>

public class MyDatabaseHelper extends SQLiteOpenHelper {
    public static final String CREATE_BOOK="create table Book("
            +"id integer primary key autoincrement," +
            "author text," +
            "price real" +
            "pages integer" +
            "name text )";
    public static final String CREATE_CATEGORY="create table Category(" +
            "id integer primary key autoincrement," +
            "category_name text," +
            "category_code integer)";
    private Context mContext;
    public MyDatabaseHelper(Context context,String name,SQLiteDatabase.CursorFactory factory,
                            int version){
        super(context,name,factory,version);
        mContext=context;
    }
    @Override
    public void onCreate(SQLiteDatabase db){
        db.execSQL(CREATE_CATEGORY);
        db.execSQL(CREATE_BOOK);
        Toast.makeText(mContext,"Create succeeded",Toast.LENGTH_LONG).show();
    }
    @Override
    public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion){
    }
}

public class MainActivity extends Activity {
    private MyDatabaseHelper dbHelper;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        dbHelper=new MyDatabaseHelper(this,"BookStore.db",null,1);
        Button createDatabase=(Button)findViewById(R.id.create_database);
        Button addData=(Button)findViewById(R.id.add_data);
        createDatabase.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                dbHelper.getWritableDatabase();
            }
        });
        addData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                ContentValues values=new ContentValues();
                values.put("name","The Da Vinci Code");
                values.put("author","Dan Brown");
                values.put("pages",454);
                values.put("price",16.96);
                db.insert("Book",null,values);
                values.clear();
            }
        });
    }
}

一个数据都没有