android-数据存储之sqlite

新建一个类继承SQLiteOpenHelper，实现三个基本方法，

public class DBHelper extends SQLiteOpenHelper {
    
    
    public static final String TABLE_NAME = "mysql";
    public static final String TITLE = "title";
    public static final String CONTEXT = "context";
    public DBHelper(@Nullable Context context) {
    
    
        super(context, "mysql.db", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
    
    
        String str = "create table mysql(_id integer primary key autoincrement,title varchar,context varchar)";
        db.execSQL(str);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    
    

    }
}

增删改查的方法

public class SQLUtils {
    
    
    private static final String TAG = "SQLUtils";
    Context context;
    private final DBHelper helper;

    public SQLUtils(Context context) {
    
    
        this.context = context;
        helper = new DBHelper(context);
    }

    public void insert(String title,String content){
    
    
        SQLiteDatabase writableDatabase = helper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(DBHelper.TITLE,title);
        values.put(DBHelper.CONTEXT,content);
        writableDatabase.insert(DBHelper.TABLE_NAME,null,values);
        writableDatabase.close();
    }

    public void delete(String position){
    
    
        SQLiteDatabase writableDatabase = helper.getWritableDatabase();
        writableDatabase.delete(DBHelper.TABLE_NAME,"_id=?",new String[]{
    
    position});
        writableDatabase.close();
    }

    public void update(String title,String content,int position){
    
    
        SQLiteDatabase writableDatabase = helper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(DBHelper.TITLE,title);
        values.put(DBHelper.CONTEXT,content);
        writableDatabase.update(DBHelper.TABLE_NAME, values, "_id=?", new String[]{
    
    String.valueOf(position)});
        writableDatabase.close();
    }

    public List<Bean> query(){
    
    
        Log.e(TAG, "query: " );
        List<Bean> list = new ArrayList<>();

        SQLiteDatabase readableDatabase = helper.getReadableDatabase();
//        Cursor query = readableDatabase.query(DBHelper.TABLE_NAME, null, null, null, null, null, null);
        Cursor cursor = readableDatabase.rawQuery("select * from " + DBHelper.TABLE_NAME, null);
        while (cursor.moveToNext()){
    
    
            String title = cursor.getString(1);
            String content = cursor.getString(2);
            Bean bean = new Bean();
            bean.setTitle(title);
            bean.setContent(content);
            list.add(bean);
        }
        return list;
    }
}