添加了对NotesProvider类的注释

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

@@ -35,6 +35,15 @@ import net.micode.notes.data.Notes.NoteColumns;
 import net.micode.notes.data.NotesDatabaseHelper.TABLE;
 
 
+/**
+ * 为存储和获取数据提供接口。可以在不同的应用程序之间共享数据
+ * ContentProvider提供的方法
+ * query：查询
+ * insert：插入
+ * update：更新
+ * delete：删除
+ * getType：得到数据类型
+ */
 public class NotesProvider extends ContentProvider {
     private static final UriMatcher mMatcher;
 
@@ -79,12 +88,19 @@ public class NotesProvider extends ContentProvider {
             + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER
             + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE;
 
+    /**
+     * 只在onCreate()中初始化Context
+     *  对mHelper进行实例化
+     */
     @Override
     public boolean onCreate() {
         mHelper = NotesDatabaseHelper.getInstance(getContext());
         return true;
     }
 
+    /**
+     *查询uri在数据库中对应的位置
+     */
     @Override
     public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
                         String sortOrder) {
@@ -112,6 +128,9 @@ public class NotesProvider extends ContentProvider {
                 break;
             case URI_SEARCH:
             case URI_SEARCH_SUGGEST:
+                /**
+                 * 不合法的参数异常
+                 */
                 if (sortOrder != null || projection != null) {
                     throw new IllegalArgumentException(
                             "do not specify sortOrder, selection, selectionArgs, or projection" + "with this query");
@@ -147,6 +166,9 @@ public class NotesProvider extends ContentProvider {
         return c;
     }
 
+    /**
+     *   插入一个uri
+     */
     @Override
     public Uri insert(Uri uri, ContentValues values) {
         SQLiteDatabase db = mHelper.getWritableDatabase();
@@ -181,6 +203,9 @@ public class NotesProvider extends ContentProvider {
         return ContentUris.withAppendedId(uri, insertedId);
     }
 
+    /**
+     * 删除一个uri
+     */
     @Override
     public int delete(Uri uri, String selection, String[] selectionArgs) {
         int count = 0;
@@ -227,6 +252,9 @@ public class NotesProvider extends ContentProvider {
         return count;
     }
 
+    /**
+     * 更新一个uri
+     */
     @Override
     public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
         int count = 0;
@@ -267,6 +295,9 @@ public class NotesProvider extends ContentProvider {
         return count;
     }
 
+    /**
+     *将字符串解析成规定格式
+     */
     private String parseSelection(String selection) {
         return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
     }
@@ -292,7 +323,7 @@ public class NotesProvider extends ContentProvider {
             }
             sql.append(selectString);
         }
-
+        /** execSQL()方法可以执行insert、delete、update和CREATE TABLE之类有更改行为的SQL语句 */
         mHelper.getWritableDatabase().execSQL(sql.toString());
     }