diff --git a/src/net/micode/notes/data/NotesProvider.java b/src/net/micode/notes/data/NotesProvider.java index edb0a60..6f81a7e 100644 --- a/src/net/micode/notes/data/NotesProvider.java +++ b/src/net/micode/notes/data/NotesProvider.java @@ -33,9 +33,10 @@ import net.micode.notes.R; import net.micode.notes.data.Notes.DataColumns; 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 public class NotesProvider extends ContentProvider { + // UriMatcher用于匹配Uri private static final UriMatcher mMatcher; private NotesDatabaseHelper mHelper; @@ -51,7 +52,9 @@ public class NotesProvider extends ContentProvider { private static final int URI_SEARCH_SUGGEST = 6; static { + // 创建UriMatcher时，调用UriMatcher(UriMatcher.NO_MATCH)表示不匹配任何路径的返回码 mMatcher = new UriMatcher(UriMatcher.NO_MATCH); + // 把需要匹配Uri路径全部给注册上 mMatcher.addURI(Notes.AUTHORITY, "note", URI_NOTE); mMatcher.addURI(Notes.AUTHORITY, "note/#", URI_NOTE_ITEM); mMatcher.addURI(Notes.AUTHORITY, "data", URI_DATA); @@ -65,6 +68,7 @@ public class NotesProvider extends ContentProvider { * x'0A' represents the '\n' character in sqlite. For title and content in the search result, * we will trim '\n' and white space in order to show more information. */ + // 声明 NOTES_SEARCH_PROJECTION private static final String NOTES_SEARCH_PROJECTION = NoteColumns.ID + "," + NoteColumns.ID + " AS " + SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA + "," + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_1 + "," @@ -72,7 +76,7 @@ public class NotesProvider extends ContentProvider { + R.drawable.search_result + " AS " + SearchManager.SUGGEST_COLUMN_ICON_1 + "," + "'" + Intent.ACTION_VIEW + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_ACTION + "," + "'" + Notes.TextNote.CONTENT_TYPE + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_DATA; - + // 声明NOTES_SNIPPET_SEARCH_QUERY private static String NOTES_SNIPPET_SEARCH_QUERY = "SELECT " + NOTES_SEARCH_PROJECTION + " FROM " + TABLE.NOTE + " WHERE " + NoteColumns.SNIPPET + " LIKE ?" @@ -80,18 +84,23 @@ public class NotesProvider extends ContentProvider { + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE; @Override + // Context只有在onCreate()中才被初始化 + // 对mHelper进行实例化 public boolean onCreate() { mHelper = NotesDatabaseHelper.getInstance(getContext()); return true; } - @Override + // 查询uri在数据库中对应的位置 public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { Cursor c = null; + // 获取可读数据库 SQLiteDatabase db = mHelper.getReadableDatabase(); String id = null; + // 匹配查找uri switch (mMatcher.match(uri)) { + // 对于不同的匹配值，在数据库中查找相应的条目 case URI_NOTE: c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null, sortOrder); @@ -113,6 +122,7 @@ public class NotesProvider extends ContentProvider { case URI_SEARCH: case URI_SEARCH_SUGGEST: if (sortOrder != null || projection != null) { + // 不合法的参数异常 throw new IllegalArgumentException( "do not specify sortOrder, selection, selectionArgs, or projection" + "with this query"); } @@ -120,6 +130,8 @@ public class NotesProvider extends ContentProvider { String searchString = null; if (mMatcher.match(uri) == URI_SEARCH_SUGGEST) { if (uri.getPathSegments().size() > 1) { + // getPathSegments()方法得到一个String的List， + // 在uri.getPathSegments().get(1)为第2个元素 searchString = uri.getPathSegments().get(1); } } else { @@ -139,6 +151,7 @@ public class NotesProvider extends ContentProvider { } break; default: + // 抛出异常 throw new IllegalArgumentException("Unknown URI " + uri); } if (c != null) { @@ -148,13 +161,17 @@ public class NotesProvider extends ContentProvider { } @Override + // 插入一个uri public Uri insert(Uri uri, ContentValues values) { + // 获得可写的数据库 SQLiteDatabase db = mHelper.getWritableDatabase(); long dataId = 0, noteId = 0, insertedId = 0; switch (mMatcher.match(uri)) { + // 新增一个条目 case URI_NOTE: insertedId = noteId = db.insert(TABLE.NOTE, null, values); break; + // 如果存在，查找NOTE_ID case URI_DATA: if (values.containsKey(DataColumns.NOTE_ID)) { noteId = values.getAsLong(DataColumns.NOTE_ID); @@ -167,6 +184,7 @@ public class NotesProvider extends ContentProvider { throw new IllegalArgumentException("Unknown URI " + uri); } // Notify the note uri + // notifyChange获得一个ContextResolver对象并且更新里面的内容 if (noteId > 0) { getContext().getContentResolver().notifyChange( ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null); @@ -177,14 +195,17 @@ public class NotesProvider extends ContentProvider { getContext().getContentResolver().notifyChange( ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null); } - + // 返回插入的uri的路径 return ContentUris.withAppendedId(uri, insertedId); } @Override + // 删除一个uri public int delete(Uri uri, String selection, String[] selectionArgs) { + //Uri代表要操作的数据，Android上可用的每种资源 -包括 图像、视频片段、音频资源等都可以用Uri来表示 int count = 0; String id = null; + // 获得可写的数据库 SQLiteDatabase db = mHelper.getWritableDatabase(); boolean deleteData = false; switch (mMatcher.match(uri)) { @@ -228,6 +249,7 @@ public class NotesProvider extends ContentProvider { } @Override + // 更新一个uri public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { int count = 0; String id = null; @@ -266,11 +288,11 @@ 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 + ')' : ""); } - + //增加一个noteVersion private void increaseNoteVersion(long id, String selection, String[] selectionArgs) { StringBuilder sql = new StringBuilder(120); sql.append("UPDATE "); @@ -292,7 +314,7 @@ 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()); }