android中的Cursor

android.database.Cursor提供了两个接口来监听数据库的变化；

<nobr style="line-height:21px">abstract void</nobr>

<nobr style="line-height:21px"><span style="line-height:21px; margin-right:2px"><a rel="nofollow" href="http://developer.android.com/reference/android/database/Cursor.html#registerContentObserver(android.database.ContentObserver)" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">registerContentObserver</a></span>(<a rel="nofollow" href="http://developer.android.com/reference/android/database/ContentObserver.html" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">ContentObserver</a>observer)</nobr> Register an observer that is called when changes happen to the content backing this cursor.

<nobr style="line-height:21px">abstract void</nobr>

<nobr style="line-height:21px"><span style="line-height:21px; margin-right:2px"><a rel="nofollow" href="http://developer.android.com/reference/android/database/Cursor.html#registerDataSetObserver(android.database.DataSetObserver)" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">registerDataSetObserver</a></span>(<a rel="nofollow" href="http://developer.android.com/reference/android/database/DataSetObserver.html" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">DataSetObserver</a>observer)</nobr> Register an observer that is called when changes happen to the contents of the this cursors data set, for example, when the data set is changed viarequery(),deactivate(), orclose().

其对应的取消监听接口如下：

<nobr style="line-height:21px">abstract void</nobr>

<nobr style="line-height:21px"><span style="line-height:21px; margin-right:2px"><a rel="nofollow" href="http://developer.android.com/reference/android/database/Cursor.html#unregisterContentObserver(android.database.ContentObserver)" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">unregisterContentObserver</a></span>(<a rel="nofollow" href="http://developer.android.com/reference/android/database/ContentObserver.html" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">ContentObserver</a>observer)</nobr> Unregister an observer that has previously been registered with this cursor viaregisterContentObserver(ContentObserver).

<nobr style="line-height:21px">abstract void</nobr>

<nobr style="line-height:21px"><span style="line-height:21px; margin-right:2px"><a rel="nofollow" href="http://developer.android.com/reference/android/database/Cursor.html#unregisterDataSetObserver(android.database.DataSetObserver)" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">unregisterDataSetObserver</a></span>(<a rel="nofollow" href="http://developer.android.com/reference/android/database/DataSetObserver.html" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">DataSetObserver</a>observer)</nobr> Unregister an observer that has previously been registered with this cursor viaregisterContentObserver(ContentObserver).

Cursor还提供了重新查询的接口：

<nobr style="line-height:21px">abstract boolean</nobr>

<nobr style="line-height:21px"><span style="line-height:21px; margin-right:2px"><a rel="nofollow" href="http://developer.android.com/reference/android/database/Cursor.html#requery()" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">requery</a></span>()</nobr> This method is deprecated. Don't use this. Just request a new cursor, so you can do this asynchronously and update your list view once the new cursor comes back.

Activity还提供了对Cursor进行管理的机制：
publicvoidstartManagingCursor(Cursorc)
Since:APILevel1
ThismethodallowstheactivitytotakecareofmanagingthegivenCursor'slifecycle
foryoubasedontheactivity'slifecycle.Thatis,whentheactivityisstopped
itwillautomaticallycalldeactivate()onthegivenCursor,
andwhenitislaterrestarteditwillcallrequery()foryou.
Whentheactivityisdestroyed,allmanagedCursorswillbeclosedautomatically.
参数
cTheCursortobemanaged.
publicfinalCursormanagedQuery(Uriuri,String[]projection,Stringselection,String[]selectionArgs,StringsortOrder)
Since:APILevel1
Wrapperaroundquery(android.net.Uri,String[],String,String[],String)thatgivestheresultingCursortocallstartManagingCursor(Cursor)sothattheactivitywillmanageitslifecycleforyou.
参数
uriTheURIofthecontentprovidertoquery.
projectionListofcolumnstoreturn.
selectionSQLWHEREclause.
selectionArgsTheargumentstoselection,ifany?sarepesent
sortOrderSQLORDERBYclause.
返回
*TheCursorthatwasreturnedbyquery().
注意：managedQuery就是查询了再调用了startManagingCursor，让Activity对Cursor进行管理。

Cursor还提供一个对数据变化进行监听的接口

<nobr style="line-height:21px">abstract void</nobr>

<nobr style="line-height:21px"><span style="line-height:21px; margin-right:2px"><a rel="nofollow" href="http://developer.android.com/reference/android/database/Cursor.html#setNotificationUri(android.content.ContentResolver,%20android.net.Uri)" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">setNotificationUri</a></span>(<a rel="nofollow" href="http://developer.android.com/reference/android/content/ContentResolver.html" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">ContentResolver</a>cr,<a rel="nofollow" href="http://developer.android.com/reference/android/net/Uri.html" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">Uri</a>uri)</nobr> Register to watch a content URI for changes.

关于setNotificationUri()函数的更多内容请参考《ContentProvider》