创建可拖拽的控件

class DraggablePanelsView : View("Draggable Panels") {
    override val root = borderpane {
        center = pane {
            add(
                    makeDraggable(LoginFrag().root as Node).apply {
                        relocate(0.0, 0.0)
                    }

            )
            add(
                    makeDraggable(ConfirmationFrag().root as Node).apply {
                        relocate(0.0, 67.0)
                    }

            )
            add(
                    makeDraggable(ProgressFrag().root as Node).apply {
                        relocate(0.0, 106.0)
                    }
            )
        }
        bottom = checkbox("Drag mode", dragModeActiveProperty)
        setPrefSize(500.0, 500.0)
        paddingAll = 10.0
        style {
            fontSize = 16.px
        }
    }
}

val dragModeActiveProperty = booleanProperty(false)
fun makeDraggable(node: Node): Node {
    val dragContext = DragContext()
    val wrapGroup = Group(node)
    wrapGroup.addEventFilter(
            MouseEvent.ANY
    ) { mouseEvent ->
        if (dragModeActiveProperty.value) { // 为所有的子节点禁用鼠标事件
            mouseEvent.consume()
        }
    }
    wrapGroup.addEventFilter(
            MouseEvent.MOUSE_PRESSED
    ) { mouseEvent ->
        if (dragModeActiveProperty.value) { // 记住鼠标光标的初始坐标和node位置
            dragContext.mouseAnchorX = mouseEvent.x
            dragContext.mouseAnchorY = mouseEvent.y
            dragContext.initialTranslateX = node.translateX
            dragContext.initialTranslateY = node.translateY
        }
    }
    wrapGroup.addEventFilter(
            MouseEvent.MOUSE_DRAGGED
    ) { mouseEvent ->
        if (dragModeActiveProperty.value) { // 通过增量计算鼠标光标动作来从初始位置移动node
            node.translateX = (dragContext.initialTranslateX
                    + mouseEvent.x
                    - dragContext.mouseAnchorX)
            node.translateY = (dragContext.initialTranslateY
                    + mouseEvent.y
                    - dragContext.mouseAnchorY)
        }
    }
    return wrapGroup
}

private class DragContext {
    var mouseAnchorX = 0.0
    var mouseAnchorY = 0.0
    var initialTranslateX = 0.0
    var initialTranslateY = 0.0
}

val styleStr = """
    -fx-background-color: white;
    -fx-border-color: black;
    -fx-border-width: 1;
    -fx-border-radius: 6;
    -fx-padding: 6;
""".trimIndent()