ADD file via upload

DbHelper.java

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+package cn.lblbc.notepad.db;
+
+import ohos.app.Context;
+import ohos.data.DatabaseHelper;
+import ohos.data.orm.OrmContext;
+import ohos.data.orm.OrmPredicates;
+
+import java.util.List;
+
+/**
+ * 厦门大学计算机专业 | 前华为工程师
+ * 专注《零基础学编程系列》  http://lblbc.cn/blog
+ * 包含：Java | 安卓 | 前端 | Flutter | iOS | 小程序 | 鸿蒙
+ * 公众号：蓝不蓝编程
+ */
+public class DbHelper {
+    private static DbHelper dbHelper = new DbHelper();
+    private OrmContext ormContext;
+
+    private DbHelper() {
+    }
+
+    public static DbHelper getInstance() {
+        return dbHelper;
+    }
+
+    public void initDb(Context context) {
+        DatabaseHelper databaseHelper = new DatabaseHelper(context);
+        ormContext = databaseHelper.getOrmContext("lblDb", "lblDb.db", NoteDatabase.class);
+    }
+
+    public void add(String content) {
+        Note note = new Note();
+        note.setId(System.currentTimeMillis());
+        note.setContent(content);
+        ormContext.insert(note);
+        ormContext.flush();
+    }
+
+    public List<Note> query() {
+        OrmPredicates ormPredicates = ormContext.where(Note.class);
+        return ormContext.query(ormPredicates);
+    }
+
+    public Note query(long noteId) {
+        OrmPredicates ormPredicates = ormContext.where(Note.class).equalTo("id", noteId + "");
+        List<Note> noteList = ormContext.query(ormPredicates);
+        Note note = null;
+        if (!noteList.isEmpty()) {
+            note = noteList.get(0);
+        }
+        return note;
+    }
+
+    public void update(Note note) {
+        ormContext.update(note);
+        ormContext.flush();
+    }
+
+    public void delete(long noteId) {
+        OrmPredicates ormPredicates = ormContext.where(Note.class).equalTo("id", noteId + "");
+        ormContext.delete(ormPredicates);
+        ormContext.flush();
+    }
+}