带有自定义ListCell的javafx ListView中的Ghost项 [英] Ghost items in javafx ListView with custom ListCell

问题描述

我尝试使用自定义ListCell在ListView中查看自定义对象。作为演示问题的示例，我选择 java.util.File 。出于演示目的，我在渲染时直接禁用ListCell。这些项目由线程模拟的外部进程添加。一切看起来都不错，直到我将CSS着色为禁用的ListCell。现在似乎有一些幽灵物品与它们被创建的ListCell一起被禁用。

I try to view a custom object in a ListView using a custom ListCell. As an example to demonstrate the problem I chose java.util.File. Also for demonstration purpose I disable the ListCell directly when rendered. The items are added by an external process simulated by the thread. Everything looks nice until I apply the CSS coloring the disabled ListCell. Now it seems that there are some ghost items which get disabled together with the ListCell they are created of.

我该如何解决这个问题？

How can I solve this?

App.java

App.java

public class App extends Application
{
    @Override
    public void start( Stage primaryStage )
    {   
        final ListView<File> listView = new ListView<>();
        listView.setCellFactory( column -> { 
            return new ListCell<File>()
            {
                protected void updateItem( File item, boolean empty )
                {   
                    super.updateItem( item, empty );

                    if( item == null || empty )
                    {
                        setGraphic( null );
                        return;
                    }

                    setDisable( true );                 
                    setGraphic( new TextField( item.getName() ) );
                }
            };
        });

        new Thread( () -> {
            for( int i=0 ; i<10 ; ++i )
            {
                try
                {
                    Thread.sleep( 1000 );
                }
                catch( Exception e )
                {
                    e.printStackTrace();
                }
                final int n = i;
                Platform.runLater( () -> {
                    listView.getItems().add( new File( Character.toString( (char)( (int) 'a' + n ) ) ) );
                });
            }       
        }).start();

        Scene scene = new Scene( listView );    
        scene.getStylesheets().add( "app.css" );

        primaryStage.setScene( scene );
        primaryStage.show();
    }

    @Override
    public void stop() throws Exception
    {
        super.stop();
    }

    public static void main( String[] args ) throws Exception
    {       
        launch( args );     
    }
}

app.css

app.css

.list-cell:disabled {
    -fx-background-color: #ddd;
}

推荐答案

你永远不会设置禁用属性返回 false 。您需要为空单元格执行此操作。以下情况可能发生在 Cell ：

You never set the disable property back to false. You need to do this for empty cells. The following could happen to a Cell:

1. 一个项目被添加到单元格并且单元格已禁用


2. 该项目已从单元格中移除， Cell 变为空，但仍保持禁用状态。

1. a item is added to the Cell and the cell is disabled
2. the item is removed from the Cell, the Cell becomes empty, but it remains disabled.

一般情况下， Cell 变为空，当添加项目时对 Cell 所做的任何更改都应该撤消。

In general when a Cell becomes empty, any changes done to the Cell when an item was added should be undone.

此外，每次将新项目分配给 Cell TextField c $ c>。

Furthermore you should avoid recreating the TextFields every time a new item is assigned to a Cell.

listView.setCellFactory(column -> {
    return new ListCell<File>() {

        private final TextField textField = new TextField();

        protected void updateItem(File item, boolean empty) {
            super.updateItem(item, empty);

            if (item == null || empty) {
                setDisable(false);
                setGraphic(null);
            } else {
                setDisable(true);
                textField.setText(item.getName());
                setGraphic(textField);
            }
        }
    };
});

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