JavaFX：StackPane顺序转换

Question

我正在尝试用fadetransion在3个不同的锚窗（单击按钮)之间切换，下面是我的代码，

public class TestSlide extends Application {
    private ObjectBinding<Node> frontNode;

    @Override
    public void start(Stage primaryStage) {

        StackPane root = new StackPane();
        AnchorPane pane1 = new AnchorPane(new Button("1"));
        AnchorPane pane2 = new AnchorPane(new Button("2"));
        AnchorPane pane3 = new AnchorPane(new Button("3"));
        root.getChildren().addAll(pane1, pane2, pane3);

        handleAnimation(root);

        BorderPane border= new BorderPane(root);

        HBox bottom = new HBox(10);
        Button front1 = new Button("Pane 1");
        Button front2 = new Button("Pane 2");
        Button front3 = new Button("Pane 3");
        front1.setOnAction((ActionEvent event) -> {
            pane1.toFront();
        });
        front2.setOnAction((ActionEvent event) -> {
            pane2.toFront();
        });
        front3.setOnAction((ActionEvent event) -> {
            pane3.toFront();
        });
        bottom.getChildren().addAll(front1, front2, front3);
        border.setBottom(bottom);

        Scene scene = new Scene(border,400,400);
        primaryStage.setScene(scene);
        primaryStage.show();

    }

    private void handleAnimation(StackPane root) {
        frontNode = Bindings.valueAt(root.getChildren(),
                Bindings.size(root.getChildren()).subtract(1));
        frontNode.addListener((obs, oldNode, newNode) -> {
            SequentialTransition fadeOutIn = new SequentialTransition();
            if (oldNode != null) {
                FadeTransition fadeOut = new FadeTransition(Duration.millis(500), oldNode);
                fadeOut.setToValue(0);
                fadeOutIn.getChildren().add(fadeOut);
            }
            if (newNode != null) {
                FadeTransition fadeIn = new FadeTransition(Duration.millis(500), newNode);
                fadeIn.setFromValue(0);
                fadeIn.setToValue(1);
                fadeOutIn.getChildren().add(fadeIn);
            }
            fadeOutIn.play();
        });
    }

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

handleanimation方法是从另一个SO帖子引用的。

现在单击窗格3按钮->转换将首先显示窗格2，然后显示窗格3。

现在单击窗格2按钮->过渡将显示pane2，上面2点中提到的问题不再出现。

为什么转换显示pane2，然后在第1和第2点显示实际的窗格？是不透明度设置的原因吗？

Answer 1

这里的问题是stackpane的子节点的初始状态是错误的：所有节点的不透明度为1。当没有动画运行时，您希望的状态是所有节点，但最后一个完全透明（不透明度=0)和最后一个完全不透明（不透明度=1)。您应该能够通过正确初始化不透明度来修复该问题：

root.getChildren().addAll(pane1, pane2, pane3);

// set opacity for all but the last child to 0
List<Node> children = root.getChildren();
for (int i = children.size()-2; i >= 0; i--) {
    children.get(i).setOpacity(0);
}

否则将发生以下情况：

就在pane1.tofront()之后。注意(SequentialTransition确保建立了动画开始的状态。

Pane 1: opacity = 0
Pane 3: opacity = 1 ------------------------------
Pane 2: opacity = 1

Pane 1: opacity = 0
Pane 3: opacity = 0
Pane 2: opacity = 1 ------------------------------

Pane 1: opacity = 1 ------------------------------
Pane 3: opacity = 0
Pane 2: opacity = 1

使用pane3.tofront()会产生类似的结果：

Pane 3: opacity = 0
Pane 1: opacity = 1 ------------------------------
Pane 2: opacity = 1

Pane 3: opacity = 0
Pane 1: opacity = 0
Pane 2: opacity = 1 ------------------------------

Pane 3: opacity = 1 ------------------------------
Pane 1: opacity = 0
Pane 2: opacity = 1