创建打开与删除数据库

《通信业务开发》课程创建打开DB创建打开数据库使用步骤PART33-2实例演示使用步骤示例继承android.database.sqlite.SQLiteOpenHelper，创建数据库操作辅助类实现onCreate()，编写SQL语句，创建数据库表等操作实现onUpdate()方法，编写SQL语句，进行数据库更新操作添加相应方法，实现DBCRUD操作Activity中事件驱动，获取可读or可写DB，调用DB操作辅助类中方法，进行CRUD操作步骤SQLite中，为表设置自动增长字段时，使用“INTEGERPRIMARYKEY”声明即可实例演示实例演示publicclassDatabaseHelperextendsSQLiteOpenHelper{

publicDatabaseHelper(Contextcontext){super(context,DATABASE_NAME,null,DATABASE_VERSION);}privatefinalstaticStringDATABASE_NAME="BOOKS.db";privatefinalstaticintDATABASE_VERSION=1;privatefinalstaticStringTABLE_NAME="books_table";publicfinalstaticStringBOOK_ID="book_id";publicfinalstaticStringBOOK_NAME="book_name";publicfinalstaticStringBOOK_AUTHOR="book_author";@OverridepublicvoidonCreate(SQLiteDatabasedb){Stringsql="CREATETABLE"+TABLE_NAME+"("+BOOK_ID+"INTEGERprimarykeyautoincrement,“+BOOK_NAME+"text,"+BOOK_AUTHOR+"text);";db.execSQL(sql);}@OverridepublicvoidonUpgrade(SQLiteDatabasedb,intoldVersion,intnewVersion){Stringsql="DROPTABLEIFEXISTS"+TABLE_NAME;db.execSQL(sql);onCreate(db);}publicCursorselect(){SQLiteDatabasedb=this.getReadableDatabase();Cursorcursor=db.query(TABLE_NAME,null,null,null,null,null,null);returncursor;……}｝DatabaseHelper.java实例演示publicclassDatabaseHelperextendsSQLiteOpenHelper{publiclonginsert(Stringbookname,Stringauthor){SQLiteDatabasedb=this.getWritableDatabase();ContentValuescv=newContentValues();cv.put(BOOK_NAME,bookname);cv.put(BOOK_AUTHOR,author);longrow=db.insert(TABLE_NAME,null,cv);returnrow;}publicvoiddelete(intid){SQLiteDatabasedb=this.getWritableDatabase();Stringwhere=BOOK_ID+"=?";String[]whereValue={Integer.toString(id)};db.delete(TABLE_NAME,where,whereValue);}publicvoidupdate(intid,Stringbookname,Stringauthor){SQLiteDatabasedb=this.getWritableDatabase();Stringwhere=BOOK_ID+"=?";String[]whereValue={Integer.toString(id)};ContentValuescv=newContentValues();cv.put(BOOK_NAME,bookname);cv.put(BOOK_AUTHOR,author);db.update(TABLE_NAME,cv,where,whereValue);}}DatabaseHelper.java实例演示publicclassMainAcextendsActivityimplementsAdapterView.OnItemClickListener{privateDatabaseHelpermBooksDB;privateCursormCursor;privateEditTextBookName;privateEditTextBookAuthor;privateListViewBooksList;privateintBOOK_ID=0;protectedfinalstaticintMENU_ADD=Menu.FIRST;protectedfinalstaticintMENU_DELETE=Menu.FIRST+1;protectedfinalstaticintMENU_UPDATE=Menu.FIRST+2;publicvoidonCreate(BundlesavedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);setUpViews();}publicvoidsetUpViews(){mBooksDB=newDatabaseHelper(this);mCursor=mBooksDB.select();}@OverridepublicbooleanonCreateOptionsMenu(Menumenu){super.onCreateOptionsMenu(menu);menu.add(Menu.NONE,MENU_ADD,0,"ADD");menu.add(Menu.NONE,MENU_DELETE,0,"DELETE");menu.add(Menu.NONE,MENU_DELETE,0,"UPDATE");returntrue;}publicbooleanonOptionsItemSelected(MenuItemitem){super.onOptionsItemSelected(item);switch(item.getItemId()){caseMENU_ADD:add();break;caseMENU_DELETE:delete();break;caseMENU_UPDATE:update();break;}returntrue;}……}MainAc.java实例演示publicclassMainAcextendsActivityimplementsAdapterView.OnItemClickListener{……publicvoidadd(){Stringbookname=BookName.getText().toString();Stringauthor=BookAuthor.getText().toString();if(bookname.equals("")||author.equals("")){return;}mBooksDB.insert(bookname,author);mCursor.requery();BooksList.invalidateViews();BookName.setText("");BookAuthor.setText("");Toast.makeText(this,"AddSuccessed!",Toast.LENGTH_SHORT).show();}publicvoiddelete(){if(BOOK_ID==0){return;}mBooksDB.delete(BOOK_ID);mCursor.requery();BooksList.invalidateViews();BookName.setText("");BookAuthor.setText("");Toast.makeText(this,"DeleteSuccessed!",Toast.LENGTH_SHORT).show();}publicvoidupdate(){Stringbookname=BookName.getText().toString();Stringauthor=BookAuthor.getText().toString();

if(bookname.equals("")||author.equals("")){return;}mBooksDB.update(BOOK_ID,bookname,author);mCursor.requery();BooksList.invalidateViews();BookName.setText("");BookAuthor.setText("");Toast.makeText(this,"UpdateSuccessed!",Toast.LENGTH_SHORT).show();}……}MainAc.java实例演示publicclassMainAcextendsActivityimplementsAdapterView.OnItemClickListener{……@OverridepublicvoidonItemClick(AdapterView<?>parent,Viewview,intposition,longid){mCursor.moveToPosition(position);BOOK_ID=mCursor.getInt(0);BookName.setText(mCursor.getString(1));BookAuthor.setText(mCursor.getString(2));}publicclassBooksListAdapterextendsBaseAdapter{privateContextmContext;privateCursormCursor;public