withValueBackReference简介

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最新推荐文章于 2025-11-26 16:17:36 发布

最新推荐文章于 2025-11-26 16:17:36 发布 · 115 阅读

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#移动开发 #数据库 #java

本文介绍如何使用ContentProviderOperation.Builder的withValueBackReference方法在Android中实现数据库批量操作时的值回引，通过示例展示了如何将一个操作的结果作为后续操作的输入。

ContentProviderOperation.Builder的 withValueBackReference函数定义如下：

<a rel="nofollow" href="http://developer.android.com/reference/android/content/ContentProviderOperation.Builder.html" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">ContentProviderOperation.Builder</a>

<a rel="nofollow" href="http://developer.android.com/reference/android/content/ContentProviderOperation.Builder.html#withValueBackReference(java.lang.String,%20int)" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">withValueBackReference</a>(<a rel="nofollow" href="http://developer.android.com/reference/java/lang/String.html" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">String</a>key, int previousResult)

Add a ContentValues back reference.

第一个参数key对应于数据库中的列名，第二个参数 previousResult代表着：回引数据库批量操作中的第previousResult个数据库操作的返回值。

总的来说就是说把批量数据库操作中的第previousResult个数据库操作的返回值作为列名为key的记录的值

<a rel="nofollow" href="http://developer.android.com/reference/android/content/ContentProviderOperation.Builder.html#withValueBackReferences(android.content.ContentValues)" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">withValueBackReferences</a>(<a rel="nofollow" href="http://developer.android.com/reference/android/content/ContentValues.html" style="color:rgb(0,102,153); line-height:21px; text-decoration:none">ContentValues</a>backReferences)

Add a ContentValuesof back references.

同上，只是把2个参数封装成一个参数。

<div style="line-height:25px">示例1：</div> <div style="line-height:25px">来源<a rel="nofollow" href="http://developer.android.com/reference/android/provider/ContactsContract.RawContacts.html" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">http://developer.android.com/reference/android/provider/ContactsContract.RawContacts.html</a> </div> <div style="line-height:25px"> <pre class="prettyprint" style="line-height:inherit; padding-top:10px; padding-right:10px; padding-bottom:10px; padding-left:10px; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); color:rgb(0,112,0); font-family:monospace; background-color:rgb(250,250,250); margin-top:1em; margin-bottom:0px; margin-left:1em; overflow-x:auto; overflow-y:auto">ArrayList<ContentProviderOperation> ops = new ArrayList<ContentProviderOperation>(); ... int rawContactInsertIndex = ops.size(); ops.add(ContentProviderOperation.newInsert(RawContacts.CONTENT_URI) .withValue(RawContacts.ACCOUNT_TYPE, accountType) .withValue(RawContacts.ACCOUNT_NAME, accountName) .build()); ops.add(ContentProviderOperation.newInsert(Data.CONTENT_URI) .withValueBackReference(Data.RAW_CONTACT_ID, rawContactInsertIndex) .withValue(Data.MIMETYPE, StructuredName.CONTENT_ITEM_TYPE) .withValue(StructuredName.DISPLAY_NAME, "Mike Sullivan") .build()); getContentResolver().applyBatch(ContactsContract.AUTHORITY, ops); </pre> <p style="line-height:1.3em; margin-top:1em; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial"> <p style="line-height:1.3em; margin-top:1em; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial"> Note the use of<code style="line-height:1em; color:rgb(0,112,0); font-family:monospace"><a rel="nofollow" href="http://developer.android.com/reference/android/content/ContentProviderOperation.Builder.html#withValueBackReference(java.lang.String,%20int)" style="color:rgb(0,102,153); line-height:23px; text-decoration:none">withValueBackReference(String, int)</a></code>to refer to the as-yet-unknown index value of the raw contact inserted in the first operation. </div> <div style="line-height:25px">结束！</div>