使用StackPane对象的绝对坐标创建路径转换

本文介绍了使用StackPane对象的绝对坐标创建路径转换的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

OrangeBlock 是一个带有文本的橙色块。它实现为 StackPane ，其中包含矩形顶部的文本。 （这种方法在 StackPane的文档中进行了演示。）

OrangeBlock is an orange block with text inside. It is implemented as a StackPane that contains text on top of a rectangle. (This approach is demonstrated in the documentation for StackPane.)

我在坐标（100,80）处放置了 OrangeBlock 试图让它平稳地移动到一些目标坐标。不幸的是，我在路上遇到了一个令人讨厌的问题：

I've placed an OrangeBlock at coordinates (100, 80) and am now trying to make it travel smoothly to some target coordinates. Unfortunately I get a nasty bump in my path:

由于某种原因， PathElement 中的坐标是相对于橙色块解释的。

For some reason the coordinates in the PathElements are interpreted relative to the orange block.

这是为什么？如何让我的 OrangeBlock 沿着绝对坐标的路径行进？下面的最小工作示例。

Why is this? And how can I make my OrangeBlock travel along a path with absolute coordinates? Minimal working example below.

import javafx.animation.PathTransition; import javafx.application.Application; import javafx.scene.*; import javafx.scene.layout.StackPane; import javafx.scene.paint.Color; import javafx.scene.shape.*; import javafx.scene.text.Text; import javafx.stage.Stage; import javafx.util.Duration; public class PathTransitionExample extends Application { @Override public void start(Stage primaryStage) throws Exception { Group root = new Group(); OrangeBlock block = new OrangeBlock(60, 40); block.relocate(100, 80); root.getChildren().add(block); PathTransition transition = newPathTransitionTo(block, 460, 320); primaryStage.setScene(new Scene(root, 600, 400)); primaryStage.show(); transition.play(); } private static PathTransition newPathTransitionTo(OrangeBlock block, double toX, double toY) { double fromX = block.getLayoutX(); double fromY = block.getLayoutY(); Path path = new Path(); path.getElements().add(new MoveTo(fromX, fromY)); path.getElements().add(new LineTo(toX, toY)); PathTransition transition = new PathTransition(); transition.setPath(path); transition.setNode(block); transition.setDelay(Duration.seconds(1)); transition.setDuration(Duration.seconds(2)); return transition; } public static void main(String[] args) { launch(args); } private static class OrangeBlock extends StackPane { public OrangeBlock(int width, int height) { Rectangle rectangle = new Rectangle(width, height, Color.ORANGE); Text text = new Text("Block"); getChildren().addAll(rectangle, text); } } }

推荐答案

我出于好奇而调试了JavaFX代码。似乎你运气不好找到合适的解决方案。以下是发生的情况：

I debugged the JavaFX code out of curiosity. Seems like you are out of luck with a proper solution. Here's what happens:

PathTransition代码有一个方法interpolate（double frac），其中包括：

The PathTransition code has a method interpolate(double frac) which includes:

cachedNode.setTranslateX(x - cachedNode.impl_getPivotX()); cachedNode.setTranslateY(y - cachedNode.impl_getPivotY());

impl_getPivotX（）和impl_getPivotY（）方法包含：

The impl_getPivotX() and impl_getPivotY() methods contain this:

public final double impl_getPivotX() { final Bounds bounds = getLayoutBounds(); return bounds.getMinX() + bounds.getWidth()/2; } public final double impl_getPivotY() { final Bounds bounds = getLayoutBounds(); return bounds.getMinY() + bounds.getHeight()/2; }

因此PathTransition始终使用节点的中心进行计算。换句话说，这适用于e。 G。一个Circle节点，但没有e。 G。一个Rectangle节点。此外，您需要layoutBounds，因此必须在边界可用后创建PathTransition。

So the PathTransition always uses the center of your node for the calculation. In other words this works with e. g. a Circle node, but not with e. g. a Rectangle node. Moreover you need the layoutBounds, so the PathTransition must be created after the bounds were made available.

您可以在PathTransition代码中看到计算都是相对的并且已经涉及布局位置。所以在你的行中你必须考虑这个。

You can see in the PathTransition code that the calculations are all relative and already involve the layout position. So in your lineTo you have to consider this.

值得注意的是LineTo类有一个方法setAbsolut（boolean）。但是它并没有解决你的问题。

Worth noting is that the LineTo class has a method setAbsolut(boolean). However it doesn't solve your problem.

所以我的问题解决方案是

So my solution to your problem would be

• 在主要阶段可见后创建PathTransition
• 修改moveTo和lineTo参数

这对我有用（我添加了一个Rectangle形状来直观地识别正确的边界）：

This works for me (I added a Rectangle shape to identify the proper bounds visually):

public class PathTransitionExampleWorking2 extends Application { @Override public void start(Stage primaryStage) throws Exception { Group root = new Group(); Rectangle rect = new Rectangle( 100, 80, 460-100+60, 320-80+40); root.getChildren().add(rect); OrangeBlock block = new OrangeBlock(60, 40); block.relocate( 100, 80); root.getChildren().add(block); primaryStage.setScene(new Scene(root, 600, 400)); primaryStage.show(); // layout bounds are used in path transition => PathTransition creation must happen when they are available PathTransition transition = newPathTransitionTo(block, 460, 320); transition.play(); } private static PathTransition newPathTransitionTo(OrangeBlock block, double toX, double toY) { double fromX = block.getLayoutBounds().getWidth() / 2; double fromY = block.getLayoutBounds().getHeight() / 2; toX -= block.getLayoutX() - block.getLayoutBounds().getWidth() / 2; toY -= block.getLayoutY() - block.getLayoutBounds().getHeight() / 2; Path path = new Path(); path.getElements().add(new MoveTo(fromX, fromY)); path.getElements().add(new LineTo(toX, toY)); PathTransition transition = new PathTransition(); transition.setPath(path); transition.setNode(block); transition.setDelay(Duration.seconds(1)); transition.setDuration(Duration.seconds(2)); return transition; } public static void main(String[] args) { launch(args); } private static class OrangeBlock extends StackPane { public OrangeBlock(int width, int height) { Rectangle rectangle = new Rectangle(width, height, Color.ORANGE); Text text = new Text("Block"); getChildren().addAll(rectangle, text); } } }

编辑：另一个解决方案是使用它而不是MoveTo和LineTo：

edit: another solution would be to use this instead of MoveTo and LineTo:

public static class MoveToAbs extends MoveTo { public MoveToAbs( Node node) { super( node.getLayoutBounds().getWidth() / 2, node.getLayoutBounds().getHeight() / 2); } } public static class LineToAbs extends LineTo { public LineToAbs( Node node, double x, double y) { super( x - node.getLayoutX() + node.getLayoutBounds().getWidth() / 2, y - node.getLayoutY() + node.getLayoutBounds().getHeight() / 2); } }

注意：你仍然需要创建创建primaryStage后的PathTransition。

Note: You still have to create the PathTransition after the primaryStage was created.

编辑：这是块移动到鼠标点击位置的另一个例子：

edit: here's another example with the block moving to the position of the mouse-click:

public class PathTransitionExample extends Application { @Override public void start(Stage primaryStage) throws Exception { Group root = new Group(); OrangeBlock block = new OrangeBlock(60, 40); block.relocate(100, 80); root.getChildren().add(block); Label label = new Label( "Click on scene to set destination"); label.relocate(0, 0); root.getChildren().add(label); Scene scene = new Scene(root, 600, 400); scene.addEventFilter(MouseEvent.MOUSE_CLICKED, new EventHandler<Event>() { PathTransition transition; { transition = new PathTransition(); transition.setNode(block); transition.setDuration(Duration.seconds(2)); } @Override public void handle(Event event) { transition.stop(); setPositionFixed(block.getLayoutX() + block.getTranslateX(), block.getLayoutY() + block.getTranslateY()); double x = ((MouseEvent) event).getX(); double y = ((MouseEvent) event).getY(); Path path = new Path(); path.getElements().add(new MoveToAbs( block)); path.getElements().add(new LineToAbs( block, x, y)); transition.setPath(path); transition.play(); } private void setPositionFixed( double x, double y) { block.relocate(x, y); block.setTranslateX(0); block.setTranslateY(0); } }); primaryStage.setScene( scene); primaryStage.show(); PathTransition transition = newPathTransitionTo(block, 460, 320); transition.play(); } private static PathTransition newPathTransitionTo(OrangeBlock block, double toX, double toY) { Path path = new Path(); path.getElements().add(new MoveToAbs( block)); path.getElements().add(new LineToAbs( block, toX, toY)); PathTransition transition = new PathTransition(); transition.setPath(path); transition.setNode(block); transition.setDelay(Duration.seconds(1)); transition.setDuration(Duration.seconds(2)); return transition; } public static void main(String[] args) { launch(args); } private static class OrangeBlock extends StackPane { public OrangeBlock(int width, int height) { Rectangle rectangle = new Rectangle(width, height, Color.ORANGE); Text text = new Text("Block"); getChildren().addAll(rectangle, text); } } public static class MoveToAbs extends MoveTo { public MoveToAbs( Node node) { super( node.getLayoutBounds().getWidth() / 2, node.getLayoutBounds().getHeight() / 2); } } public static class LineToAbs extends LineTo { public LineToAbs( Node node, double x, double y) { super( x - node.getLayoutX() + node.getLayoutBounds().getWidth() / 2, y - node.getLayoutY() + node.getLayoutBounds().getHeight() / 2); } } }