noteslistactivity

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

@@ -35,7 +35,7 @@ import net.micode.notes.data.Notes.NoteColumns;
 import net.micode.notes.data.NotesDatabaseHelper.TABLE;
 
 /**
- *
+ *定义便签提供者类
  */
 public class NotesProvider extends ContentProvider {
     private static final UriMatcher mMatcher;
@@ -81,18 +81,25 @@ public class NotesProvider extends ContentProvider {
         + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER
         + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE;
 
+    //重写onCreate方法，实例化类时调用
+    //获取便签数据库
     @Override
     public boolean onCreate() {
         mHelper = NotesDatabaseHelper.getInstance(getContext());
         return true;
     }
 
+    //重写查询方法
+    //@ selection 查询条件，之前的字符串常量
     @Override
     public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
             String sortOrder) {
+        //游标置空
         Cursor c = null;
+        //以可读方式打开数据库
         SQLiteDatabase db = mHelper.getReadableDatabase();
         String id = null;
+        //选择判断uri
         switch (mMatcher.match(uri)) {
             case URI_NOTE:
                 c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
@@ -137,6 +144,7 @@ public class NotesProvider extends ContentProvider {
                     c = db.rawQuery(NOTES_SNIPPET_SEARCH_QUERY,
                             new String[] { searchString });
                 } catch (IllegalStateException ex) {
+                    //将错误信息写入日志，便于查错
                     Log.e(TAG, "got exception: " + ex.toString());
                 }
                 break;
@@ -149,8 +157,10 @@ public class NotesProvider extends ContentProvider {
         return c;
     }
 
+    //该方法实现了向特定uri地址插入内容
     @Override
     public Uri insert(Uri uri, ContentValues values) {
+        //以写入方式打开数据库
         SQLiteDatabase db = mHelper.getWritableDatabase();
         long dataId = 0, noteId = 0, insertedId = 0;
         switch (mMatcher.match(uri)) {
@@ -166,6 +176,7 @@ public class NotesProvider extends ContentProvider {
                 insertedId = dataId = db.insert(TABLE.DATA, null, values);
                 break;
             default:
+                //uri无效，抛出异常
                 throw new IllegalArgumentException("Unknown URI " + uri);
         }
         // Notify the note uri
@@ -183,11 +194,13 @@ public class NotesProvider extends ContentProvider {
         return ContentUris.withAppendedId(uri, insertedId);
     }
 
+    //重写删除方法，根据选择条件删除指定内容
     @Override
     public int delete(Uri uri, String selection, String[] selectionArgs) {
         int count = 0;
         String id = null;
         SQLiteDatabase db = mHelper.getWritableDatabase();
+        //创建是否删除标识
         boolean deleteData = false;
         switch (mMatcher.match(uri)) {
             case URI_NOTE:
@@ -229,11 +242,14 @@ public class NotesProvider extends ContentProvider {
         return count;
     }
 
+    //重写更新方法，更新数据库中的内容
     @Override
     public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
         int count = 0;
         String id = null;
         SQLiteDatabase db = mHelper.getWritableDatabase();
+        //创建是否更新标识
+        //false - 未更新
         boolean updateData = false;
         switch (mMatcher.match(uri)) {
             case URI_NOTE:
@@ -273,6 +289,7 @@ public class NotesProvider extends ContentProvider {
         return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
     }
 
+    //私有方法，更新便签版本
     private void increaseNoteVersion(long id, String selection, String[] selectionArgs) {
         StringBuilder sql = new StringBuilder(120);
         sql.append("UPDATE ");