Question

在下面的代码中，presentsAlbumIndex用于控制TileList的selectedIndex。最初选择项目“五”。每当按下按钮时，数组中的第一项将被删除，并且presentAlbumIndex将递减。

理论上，每次单击按钮时，所选索引应保持“五”（直到“五”本身被删除）。它按照第一次按下按钮的方式工作。但是，在第二个按钮上，由于某种原因按突出显示更改为“六”。此外，TileList selectedIndex总是一个落后。

为什么？

我尝试查看ListBase并监控selectedIndex。看起来selectedIndex 最初更新为正确的索引，但随后它会在某个时刻恢复到正确的索引+ 1。我不知道为什么会退缩。

这似乎是因为我在同一操作中进行数据提供程序删除和索引更改。

TileList中是否有一些函数我可以覆盖以使selectedIndex保持最新状态？

史蒂夫

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="absolute"
        applicationComplete="init()">
    <mx:Label id="label1" text="{'TileList selected index: ' + albumsThumbnailList.selectedIndex}"
        x="255" y="55" width="234"/>
    <mx:Label id="label2" text="{'Presented album index: ' + presentedAlbumIndex}" x="255" y="81" width="234"/>
    <mx:TileList id="albumsThumbnailList" direction="vertical"
        dataProvider="{presentedAlbums}"
        selectedIndex="{presentedAlbumIndex}" x="25" y="13"
        change="presentedAlbumIndex=albumsThumbnailList.selectedIndex"
        height="400"/>
    <mx:Button click="test2()" x="297" y="150"/>

    <mx:Script>
        <![CDATA[
            import mx.events.CollectionEvent;
            import mx.collections.ArrayCollection;
            private var _includedAlbums:ArrayCollection = new
                ArrayCollection(["zero","one","two","three","four","five","six","seven"]);

            [Bindable]
            private var presentedAlbumIndex:int = 5;

            private function init():void {

                _includedAlbums.addEventListener(CollectionEvent.COLLECTION_CHANGE,
                    function():void {
                        dispatchEvent(new Event("albumDataChanged"));
                    }
                );
            }

            public function test2():void {
                _includedAlbums.removeItemAt(0);
                presentedAlbumIndex--;
            }

           [Bindable(event="albumDataChanged")]
           public function get presentedAlbums():ArrayCollection {
               return _includedAlbums;
           }

        ]]>
    </mx:Script>

</mx:Application>

Answer 1

使用COLLECTION_CHANGED侦听器，List会获取一个新的dataProvider，因为这是一个异步事件，它会在selectedIndex上绑定后触发。通过删除此侦听器并在集合更改时不提供新的集合dataProvider，selectedIndex绑定按预期运行。

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="absolute"
        applicationComplete="init()">
    <mx:Label id="label1" text="{'TileList selected index: ' + albumsThumbnailList.selectedIndex}"
        x="255" y="55" width="234"/>
    <mx:Label id="label2" text="{'Presented album index: ' + presentedAlbumIndex}" x="255" y="81" width="234"/>
    <mx:TileList id="albumsThumbnailList" direction="vertical"
        dataProvider="{presentedAlbums}" x="25" y="13" 
        selectedIndex="{presentedAlbumIndex}"
        height="400"/>
    <mx:Button click="test2()" x="297" y="150"/>

    <mx:Script>
        <![CDATA[
            import mx.events.CollectionEvent;
            import mx.collections.ArrayCollection;
            private var _includedAlbums:ArrayCollection = new
                ArrayCollection(["zero","one","two","three","four","five","six","seven"]);

            [Bindable]
            private var presentedAlbumIndex:int = 5;

            private function init():void {

            }

            public function test2():void {
                _includedAlbums.removeItemAt(0);
                presentedAlbumIndex--;
            }

           [Bindable(event="albumDataChanged")]
           public function get presentedAlbums():ArrayCollection {
               return _includedAlbums;
           }

        ]]>
    </mx:Script>

</mx:Application>

为什么我的TileList selectedIndex没有更新？

1 个答案: