JavaFX 过渡动画等待

Question

这么快，我正在做一个演示计算机绘图方法的程序。我需要创建时间轴或动作历史，例如（placeVertex(x,y)、moveVertex(newX,newY) 等）并迭代（向前和向后，自动或手动）

我已经通过使用命令设计模式实现了这一点，但这些命令中很少有使用转换的。第一个想法是在每个命令之间 setOnFinished 中使用 Condition 接口的锁定、等待和信号，但它导致 gui 冻结。

我尝试了 SequentialTransition，但它对我的问题没有用 - 无法在转换之间动态更改属性。

是否有可能以某种方式通知一代人一个过渡结束，下一个可以运行而无需 GUI 冻结和绘制？

谢谢！

编辑：我会尽量简化这一切这是我的命令界面和这些命令之一：

 public interface Command {
        public void execute();
  }

 public class MoveVertex implements Command {
        public MoveVertex(Data d, Vertex v, double changedX, double changedY){..};

        @Override
        public void execute() {         
            Path path = new Path();         
            path.getElements().add(new MoveTo(v.getCenterX(), v.getCenterY()));
            path.getElements().add(new LineTo(changedX, changedY));

            PathTransition pathTransition = new PathTransition();   
            pathTransition.setDuration(Duration.millis(velocity)); 
            pathTransition.setPath(path);   
            pathTransition.setNode(v.getVertex());

            pathTransition.play();  }
  }

这些命令存储在我的历史记录中 class 基本上是

private List<Command> history;

我确实会浏览列表并执行命令

public boolean executeNext() {
    if (history.size() != position) {
        history.get(position).execute();
        position++;
        return true;
    }
    return false;
}

并且我试图在下一个命令开始时达到状态，只有在上一个命令完成的情况下。试图将 await/signal 置于两者之间但没有成功。

Answer 1

下面的解决方案使用了 Itachi 的建议，即提供一个 onFinished 处理程序，以便在我们到达下一个位置后将节点移动到新的（随机）位置。

通过重新使用单个 Transition 而不是在事件处理程序中使用递归，它可能会变得更高效（也更容易理解）。可能没有必要为每个动作创建一个新的 Transition - 但是，只要没有数十万次动作迭代，它应该是可以接受的。

import javafx.animation.*;
import javafx.application.Application;
import javafx.event.*;
import javafx.geometry.Point2D;
import javafx.scene.*;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.*;
import javafx.stage.Stage;
import javafx.util.Duration;

import java.util.Random;

// animates moving a node forever in a random walk pattern.
public class RandomWalk extends Application {

    private static final Random random = new Random(42);

    private static final double W = 200;
    private static final double H = 200;
    private static final double R = 10;

    private static final Node node = new Circle(
            R, Color.FORESTGREEN
    );

    @Override
    public void start(Stage stage) {
        // start from the center of the screen.
        node.relocate(W / 2 - R, H / 2 - R);

        stage.setScene(new Scene(new Pane(node), W, H));
        stage.show();

        walk();
    }

    // start walking from the current position to random points in sequence.
    private void walk() {
        final Point2D to = getRandomPoint();
        final Transition transition = createMovementTransition(
                node,
                to
        );

        transition.setOnFinished(
                walkFrom(to)
        );
        transition.play();
    }

    private EventHandler<ActionEvent> walkFrom(final Point2D from) {
        return event -> {
            // Finished handler might be called a frame before transition complete,
            // leading to glitches if we relocate in the handler.
            // The transition works by manipulating translation values,
            // so zero the translation out before relocating the node.
            node.setTranslateX(0);
            node.setTranslateY(0);

            // After the transition is complete, move the node to the new location.
            // Relocation co-ordinates are adjusted by the circle's radius.
            // For a standard node, the R adjustment would be unnecessary 
            // as most nodes are located at the top left corner of the node 
            // rather than at the center like a circle is.
            node.relocate(
                    from.getX() - R,
                    from.getY() - R
            );

            // Generate the next random point and play a transition to walk to it.
            // I'd rather not use recursion here as if you recurse long enough,
            // then you will end up with a stack overflow, but I'm not quite sure
            // how to do this without recursion.
            final Point2D next = getRandomPoint();
            final Transition transition = createMovementTransition(node, next);
            transition.setOnFinished(walkFrom(next));
            transition.play();
        };
    }

    // We use a PathTransition to move from the current position to the next.
    // For the simple straight-line movement we are doing,
    // a straight TranslateTransition would have been fine.
    // A PathTransition is just used to demonstrate that this
    // can work for the generic path case, not just straight line movement.
    private Transition createMovementTransition(Node node, Point2D to) {
        Path path = new Path(
                new MoveTo(
                        0,
                        0
                ),
                new LineTo(
                        to.getX() - node.getLayoutX(),
                        to.getY() - node.getLayoutY()
                )
        );

        return new PathTransition(
                Duration.seconds(2),
                path,
                node
        );
    }

    // @return a random location within a bounding rectangle (0, 0, W, H)
    // with a margin of R kept between the point and the bounding rectangle edge.
    private Point2D getRandomPoint() {
        return new Point2D(
                random.nextInt((int) (W - 2*R)) + R,
                random.nextInt((int) (H - 2*R)) + R
        );
    }

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

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