选项卡未处于活动状态时未定义的元素 [英] Undefined element when tab is not active

问题描述

当我尝试访问 Tab 元素的子元素时，如果它不是活动的，QML 会抛出一个错误，说是 undefined.

When I try to access a son of a Tab element, if it is not active QML throws an error saying is undefined.

main.qml

import QtQuick 2.4
import QtQuick.Controls 1.3
import QtQuick.Window 2.0

    ApplicationWindow {
        TabView {
            Tab {
                id: mytab1
            }
            Tab {
                id: myTab2
                Rectangle {
                    //(...)
                }
            }
        }

        Connections {
            target: eventManager

            onData: {
                var scene = myTab2.children[0];
                console.log(scene);
            }
        }
    }

因此，如果 myTab2 处于活动状态，我可以在控制台中看到 QQuickItem_QML_15(0x27f1e2e0).如果 myTab2 未激活，则 qml 将抛出 TypeError: Cannot read property 'children' of undefined.

So, if myTab2 is active, I can see in the console QQuickItem_QML_15(0x27f1e2e0). If myTab2 is not active, then qml throws TypeError: Cannot read property 'children' of undefined.

如果选项卡未处于活动状态，为什么未定义，我该如何解决?

Why is undefined if the tab is not active and how can I fix it?

谢谢！

推荐答案

来自 Qt 文档 网站，我找到了解决方案.

From the Qt documentation website, I've found a solution.

标签被延迟加载；仅已成为当前选项卡(对于例如，通过单击它们)将具有有效的内容.你可以强迫通过将 active 属性设置为 true 来加载标签:

Tabs are lazily loaded; only tabs that have been made current (for example, by clicking on them) will have valid content. You can force loading of tabs by setting the active property to true:

import QtQuick 2.4
import QtQuick.Controls 1.3
import QtQuick.Window 2.0

ApplicationWindow {
    TabView {
        Tab {
            id: mytab1
            active: true
        }
        Tab {
            id: myTab2
            active: true
            Rectangle {
                //(...)
            }
        }
    }

    Connections {
        target: eventManager

        onData: {
            var scene = myTab2.children[0];
            console.log(scene);
        }
    }
}

所以，我在两个选项卡中都添加了属性 active: true，它工作正常！

So, I've added the property active: true in both tabs, and It works fine!

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