android sqlite

新建一个class extends SQLiteOpener

getWritableDatabase function 可以打开资料库

public class MySQLiteHelper extends SQLiteOpenHelper {//    public static final String TABLE_COMMENTS = "comments";//    public static final String COLUMN_ID = "_id";//    public static final String COLUMN_COMMENT = "comment";////    private static final String DATABASE_NAME = "commments.db";//    private static final int DATABASE_VERSION = 1;    public MySQLiteHelper(Context context,String name,SQLiteDatabase.CursorFactory factory,int version) {        super(context, name,factory,version);              //上下文 资料库名 cursor 版本号        mContext=context;    }    // Database creation sql statement    private static final String CREATE_BOOK = "create table BOOK"            + "("            + " id integer primary key autoincrement, " + "author text,"            +"price real,"            +"pages integer,"            +"name text);";    private static final String CREATE_CATEGORY = "create table Category"            + "("            + " id integer primary key autoincrement, " + "category text,"            +"category_code integer);";    private Context mContext;    @Override    public void onCreate(SQLiteDatabase database) {        database.execSQL(CREATE_BOOK);        database.execSQL(CREATE_CATEGORY);        Toast.makeText(mContext,"sussed",Toast.LENGTH_SHORT).show();    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        Log.w(MySQLiteHelper.class.getName(),                "Upgrading database from version " + oldVersion + " to "                        + newVersion + ", which will destroy all old data");        db.execSQL("DROP TABLE IF EXISTS BOOK" );        db.execSQL("DROP TABLE IF EXISTS Category" );        onCreate(db);    }}

public class MainActivity extends AppCompatActivity {    private MySQLiteHelper dbHelper;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        dbHelper = new MySQLiteHelper(this, "BookStore.db", null, 3);        Button create=(Button) findViewById(R.id.create);                create.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                dbHelper.getWritableDatabase();            }        });                Button add=(Button) findViewById(R.id.add);        Button update=(Button) findViewById(R.id.up);                update.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                SQLiteDatabase database=dbHelper.getWritableDatabase();                 ContentValues values=new ContentValues();                 values.put("price",11);                 database.update(                         "Book",values,"name=?",new String[]{                                 "uuko"                         });            }        });                Button del =(Button)findViewById(R.id.del);        Button query=(Button) findViewById(R.id.query);        query.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                SQLiteDatabase database=dbHelper.getWritableDatabase();                Cursor cursor=database.query("Book",                        null,null,null,                        null,null,null);                        //表 列 where条件 具体值 groupby having orderby                if (cursor.moveToFirst()){                    do {                        String name=cursor.getString(cursor.getColumnIndex("name"));                        Log.d("MainActivity", "onClick: "+name);                    }while (cursor.moveToNext());                }                cursor.close();            }        });        del.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                SQLiteDatabase database=dbHelper.getWritableDatabase();                ContentValues values=new ContentValues();                database.delete("Book","pages>?",new String[] {"500"});            }        });//        add.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                SQLiteDatabase database=dbHelper.getWritableDatabase();                ContentValues values=new ContentValues();                //组装数据                values.put("name","uuko");                values.put("author","yy");                values.put("pages",444);                values.put("price",10.55);                database.insert("Book",null,values);                values.put("name","ttt");                values.put("author","tt");                values.put("pages",41);                values.put("price",3.55);                database.insert("Book",null,values);            }        });    }}