javafx有一个eventfilter自身删除 [英] javafx have an eventfilter remove itself

问题描述

我的代码片段如下：

//button clicked method
@FXML
public void newHeatExchanger2ButtonClicked(ActionEvent event) throws Exception {

    //new pane created
    Pane pane = new Pane();

    //method call everytime the button is clicked
    create2DExchanger(pane);

   }

//method declaration
private void create2DExchanger(Pane pane) {

    EventHandler<MouseEvent> panePressed = (e -> {
        if (e.getButton() == MouseButton.SECONDARY){

            do stuff
        }

        if (e.getButton() == MouseButton.PRIMARY){
            do stuff
        }
    });

    EventHandler<MouseEvent> paneDragged = (e -> {
        if (e.getButton() == MouseButton.PRIMARY){
            do stuff
        }
    });
    EventHandler<MouseEvent> paneReleased = (e -> {
        if (e.getButton() == MouseButton.PRIMARY){
            do stuff;
        }

    });
    EventHandler<MouseEvent> paneMoved = (t -> {
        do stuff;
    });
    EventHandler<MouseEvent> paneClicked = (t -> {
        //I need this filter to remove itself right here
        t.consume();
        pane.removeEventFilter(MouseEvent.MOUSE_MOVED, paneMoved);
        pane.addEventHandler(MouseEvent.MOUSE_PRESSED, panePressed);
        pane.addEventHandler(MouseEvent.MOUSE_DRAGGED, paneDragged);
        pane.addEventHandler(MouseEvent.MOUSE_RELEASED, paneReleased);
    });
    pane.removeEventHandler(MouseEvent.MOUSE_PRESSED, panePressed);
    pane.removeEventHandler(MouseEvent.MOUSE_DRAGGED, paneDragged);
    pane.removeEventHandler(MouseEvent.MOUSE_RELEASED, paneReleased);
    pane.addEventFilter(MouseEvent.MOUSE_MOVED, paneMoved);
    pane.addEventFilter(MouseEvent.MOUSE_PRESSED, paneClicked);


}

最初我将窗格设置为仅mouse_moved和mouse_pressed的事件过滤器。一旦鼠标点击，我需要鼠标过滤器mouse_pressed和mouse_moved来消除，并添加eventHandlers像我在窗格单击过滤器llamda。我需要第一组事件作为过滤器，因为有孩子节点我不想接收事件（即在窗格的孩子的弧上的事件过滤器）。第二组需要处理程序，因为arc事件过滤器需要在事件窗格接收到事件之前消耗事件。

Initially I set the pane to have only the event filters of mouse_moved, and mouse_pressed. As soon as the mouse is clicked I need the mouse filter for mouse_pressed and mouse_moved to go away and add the eventHandlers as I do in the paneClicked filter llamda. I need the first set of events to be filters because there are children nodes I do not want to receive the event (i.e. an event filter on an arc that is a child of the pane). The second set need to be handlers because the arc event filter needs to consume the event before the pane eventHandlers receive it.

便利事件如：

    pane.setOnMousePressed() 

可以通过调用

    pane.setOnMousePressed(null); 

但是我需要这个初始事件过滤器来删除自己。我将需要在代码中删除自己的事件的功能，但是如果我尝试添加

but I need this initial event filter to remove itself. I will need the functionality of an event removing itself later as well in the code, but if I try to add

    pane.removeEventFilter(MouseEvent.MOUSE_PRESSED, paneClicked);

至

    EventHandler<MouseEvent> paneClicked = (t -> {
        //I need this filter to remove itself right here
        t.consume();
        pane.removeEventFilter(MouseEvent.MOUSE_MOVED, paneMoved);
        pane.addEventHandler(MouseEvent.MOUSE_PRESSED, panePressed);
        pane.addEventHandler(MouseEvent.MOUSE_DRAGGED, paneDragged);
        pane.addEventHandler(MouseEvent.MOUSE_RELEASED, paneReleased);
    });

它不会编译。我一直在研究几天，了解如何获取eventFilter或eventHandler的功能，以消除自身，但我很快就会发现。我还没有在我的Google搜索中找到任何网络或stackexchange。我真的很感激能够把这件事看出来。谢谢。

It will not compile. I have been researching for a couple of days on how to get the functionality of an eventFilter or eventHandler to remove itself but I am coming up short. I have not found anything online or on stackexchange in my Google searches either. I would really appreciate being able to figure this thing out. Thanks.

推荐答案

我相信这个问题起因于你试图访问 paneClicked 在完全声明之前。

I believe the problem stems from the fact that you try to access paneClicked before it was fully declared.

您可以使用此关键字的匿名类来克服此问题：

You can overcome this using an anonymous class with the this keyword:

EventHandler<MouseEvent> paneClicked =  new EventHandler<MouseEvent>() {
    @Override
    public void handle(MouseEvent event) {
        event.consume();
        pane.removeEventFilter(MouseEvent.MOUSE_PRESSED, this);
        pane.removeEventFilter(MouseEvent.MOUSE_MOVED, paneMoved);
        pane.addEventHandler(MouseEvent.MOUSE_PRESSED, panePressed);
        pane.addEventHandler(MouseEvent.MOUSE_DRAGGED, paneDragged);
        pane.addEventHandler(MouseEvent.MOUSE_RELEASED, paneReleased);
    }
};

或通过引用完全限定的静态功能：

Or by referencing a fully qualified static function:

public class ContainingClass {
    ...
    private static EventHandler<MouseEvent> paneClicked = (t -> {
        t.consume();
        pane.removeEventFilter(
            MouseEvent.MOUSE_PRESSED, ContainingClass.paneClicked
        );
    });
}

另见：

• 为什么Java 8中的lambdas不允许对匿名类不成员变量的引用？


• Java8 Lambdas vs匿名类

• Why do lambdas in Java 8 disallow forward reference to member variables where anonymous classes don't?
• Java8 Lambdas vs Anonymous classes

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