我有一个容器，它在运行时被动态创建的组件填充。每个元素（让我们称之为DynamicObject）都有一个子元素树（Node s），也是动态创建的。更重要的是，Node组件可以彼此嵌套（如树结构）。
让容器将id参数设置为"main_container"，并将每个DynamicObject设置为"dynamic_object"。
每当我尝试从任何嵌套的main_container元素中解决Node时，一切正常。问题是当我尝试从根dynamic_object以外的任何Node处理dynamic_object时（main_container的直接后代/子项）。结果是：
ReferenceError：未定义dynamic_object
我的问题是：这种行为背后可能是什么原因？它可以与这些对象动态创建的事实有关吗？ （这是我的第一个想法，因为我总能解决// Container.qml
import "container_logic.js" as Logic
Rectangle {
id: main_container
Keys.onTabPressed: {
Logic.createComponent("DynamicObject.qml", {/* some parameters */});
var dynamic_object = Logic.object;
Logic.createComponent("Node.qml",{labelText: "asdefg"}, undefined, dynamic_object)
var asdefg = Logic.object;
Logic.createComponent("Node.qml",{labelText: "tree A"}, undefined, dynamic_object)
var tree_a = Logic.object;
Logic.createComponent("Node.qml",{labelText: "a"}, undefined, asdefg)
var a = Logic.object;
Logic.createComponent("Node.qml",{labelText: "s"}, undefined, asdefg)
var s = Logic.object;
asdefg.subnodes = [a, s]
Logic.createComponent("Node.qml",{labelText: "tree B", isInput: false}, undefined, dynamic_object)
var tree_b = Logic.object;
Logic.createComponent("Node.qml",{labelText: "xyz", isInput: false}, undefined, dynamic_object)
var xyz = Logic.object;
Logic.createComponent("Node.qml",{labelText: "x", isInput: false}, undefined, xyz)
var x = Logic.object;
Logic.createComponent("Node.qml",{labelText: "y", isInput: false}, undefined, xyz)
var y = Logic.object;
Logic.createComponent("Node.qml",{labelText: "z", isInput: false}, undefined, xyz)
var z = Logic.object;
xyz.subnodes = [x,y,z]
dynamic_object.treeLeft = [asdefg, tree_a]
dynamic_object.treeRight = [tree_b, xyz]
}
}
// DynamicObject.qml
Rectangle {
id: dynamic_object
property alias treeLeft : tree_left.subnodes
property alias treeRight: tree_right.subnodes
Rectangle {
id: content_area
Node {
id: tree_left
labelText: "left"
anchors.left: parent.left
}
Node {
id: tree_right
labelText: "right"
anchors.right: parent.right
}
}
}
// Node.qml
ColumnLayout {
id: node
default property alias subnodes: subnodes_area.data
property alias labelText: label.text
Rectangle {
id: header_area
Text {
id: label
}
MouseArea {
id: mouse_area
anchors.fill: parent
hoverEnabled: true
onHoveredChanged: {
console.debug(main_container) // works fine
console.debug(dynamic_object) // **generates the error for all nodes but the root one**
}
}
}
ColumnLayout {
id: subnodes_area
anchors.top: header_area.bottom
}
}
// container_logic
var component = null
var owner = main_container
var object = null
var data = null
function createComponent(type, info, callback, container) {
callback = callback || finishComponent
owner = container || main_container
if(component != null) {
console.log("Error: a component is being loaded at this time");
return;
}
component = Qt.createComponent(type)
data = info
if(component.status === Component.Ready) {
callback()
} else if(component.status === Component.Loading) {
component.statusChanged.connect(callback)
} else {
console.log("Error loading component:", component.errorString())
}
}
function finishComponent() {
if(component.status === Component.Ready) {
object = component.createObject(owner, data)
if(object === null) {
console.log("Error creating object")
}
} else if(component.status === Component.Error) {
console.log("Error loading component:", component.errorString())
}
resetData()
}
function resetData() {
component = null;
data = null;
}
并且它在qml代码中被静态声明。）
代码示例：（如果有任何遗漏，请在评论中告诉我）
{{1}}
答案 0 :(得分：4)
根据http://qt-project.org/doc/qt-4.8/qdeclarativedynamicobjects.html：
- 如果使用Qt.createComponent（），则创建上下文是调用此方法的QDeclarativeContext
- 如果定义了Component {}项并且在该项上调用了createObject（），则创建上下文是定义Component的上下文
问题是每个后续createComponent()的{{1}}函数是从Node的上下文调用的，因此阻止了后代能够解析main_container标识。
通过将负责创建嵌套dynamic_object的代码移动到Node文件（实际上是由该qml文档导入的javascript文件，但结果相同）解决了这个问题。