Update NotesDatabaseHelper.java

app/src/main/java/net/micode/notes/data/NotesDatabaseHelper.java

@@ -28,20 +28,22 @@ import net.micode.notes.data.Notes.NoteColumns;
 
 
 public class NotesDatabaseHelper extends SQLiteOpenHelper {
-    private static final String DB_NAME = "note.db";
+    private static final String DB_NAME = "note.db";// 数据库名称
+
+    private static final int DB_VERSION = 4; // 数据库版本号
 
-    private static final int DB_VERSION = 4;
 
     public interface TABLE {
-        public static final String NOTE = "note";
+        public static final String NOTE = "note";// 笔记表
 
-        public static final String DATA = "data";
+        public static final String DATA = "data"; // 数据表
     }
 
-    private static final String TAG = "NotesDatabaseHelper";
+    private static final String TAG = "NotesDatabaseHelper";// 日志标签
 
-    private static NotesDatabaseHelper mInstance;
+    private static NotesDatabaseHelper mInstance;// 数据库帮助类实例
 
+// 创建笔记表的 SQL 语句
     private static final String CREATE_NOTE_TABLE_SQL =
         "CREATE TABLE " + TABLE.NOTE + "(" +
             NoteColumns.ID + " INTEGER PRIMARY KEY," +