在之前提供了小例子BookProvider,我们回过头看看如何将通过该Content Provider进行数据的读取。
(1)增加
private void addBook(String name ,String isbn,String author){ /* 从ContentProvider的insert()方法的参数可以看到,通过ContentValues来进行数据的传递。ContentValues是key/values对,可以存储多个组,非常适合传递信息 */ ContentValues cv = new ContentValues(); cv.put(BookTableMetaData.BOOK_NAME, name); cv.put(BookTableMetaData.BOOK_ISBN, isbn); cv.put(BookTableMetaData.BOOK_AUTHOR, author); /* ContentResolver负责将URI reference解析到正确的provider上,并对该provider的公开的读写接口进行操作。它的方法和provider提供的方法一一对应,并增加了uri参数。*/ ContentResolver cr = getContentResolver(); Uri insertUri = cr.insert(BookProviderMetaData.BookTableMetaData.CONTENT_URI, cv); //对应BookProvider的insert() } |
(2)删除
private void delBook(String name){ ContentResolver cr = getContentResolver(); int count = cr.delete(BookProviderMetaData.BookTableMetaData.CONTENT_URI, /* Uri uri */ BookTableMetaData.BOOK_NAME + "=?", /* String WhereClause */ new String[]{name}); /* String[] selectionArgs */ } |
(3)修改: update和insert非常相似,也是通过ContentValues传递修改内容。
private void updateBookIsbn(String name ,String newIsbn,String newAuthor){ ContentValues cv = new ContentValues(); cv.put(BookTableMetaData.BOOK_NAME, name); cv.put(BookTableMetaData.BOOK_ISBN, newIsbn); cv.put(BookTableMetaData.BOOK_AUTHOR, newAuthor); ContentResolver cr = getContentResolver(); int count = cr.update(BookProviderMetaData.BookTableMetaData.CONTENT_URI, /* Uri uri */ cv, /* ContentValues values */ BookTableMetaData.BOOK_NAME + "=?", /* String WhereClause */ new String[]{name}); /* String[] selectionArgs */ } |
(4)查询
private void showBooks(){ Uri uri = BookProviderMetaData.BookTableMetaData.CONTENT_URI; /*方式一,通过managedQuery( )*/ @SuppressWarnings("deprecation") Cursor c = managedQuery(uri, null, null, null, null); /* 方式二:利用ContentResolver的query来获取*/ // ContentResolver cr = getContentResolver(); // Cursor c = cr.query(uri, null, null, null, null); int iIndex = c.getColumnIndex(BookTableMetaData._ID); int iName = c.getColumnIndex(BookTableMetaData.BOOK_NAME); int iIsbn = c.getColumnIndex(BookTableMetaData.BOOK_ISBN); int iAuthor = c.getColumnIndex(BookTableMetaData.BOOK_AUTHOR); /* 需要注意,通过下面showInfo显示,各列的Id并非按我们的创建table的列的顺序,所以一定要先获取列的ID。至于row的_id,是按顺序提供,为当前最大的_id+1。但除非我们能很明确清楚,一般不使用这些系统内部安排的Id */ |
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转自http://blog.csdn.net/flowingflying/article/details/9243275