c++ - View 如何在幕后更新？

Question

因此，例如，当我在 QLabel 上使用 setText() 时，Qt 会自动为我更新 View /gui 并显示新文本，但幕后发生了什么？在使用 setText() 等函数时，是否有自动调用的更新函数？

谢谢!!

Answer 1

您应该查看此 link 中的基本文档.

内部系统稍微复杂一点，但总的来说，它遵循观察者模式。这种机制允许检测用户 Action 或改变状态，并响应这个 Action 。

低级交互，如刷新屏幕，是通过 Event System 实现的

In Qt, events are objects, derived from the abstract QEvent class, that represent things that have happened either within an application or as a result of outside activity that the application needs to know about. Events can be received and handled by any instance of a QObject subclass, but they are especially relevant to widgets. This document describes how events are delivered and handled in a typical application.

所以，关于显示过程，有一个专门的事件。 QWidget 对象处理/订阅 PaintEvent，参见 QWidget::paintEvent .

This event handler can be reimplemented in a subclass to receive paint events passed in event. A paint event is a request to repaint all or part of a widget.

当您调用 QLineEdit::setText() 时，将在下次触发显示事件时根据操作系统配置、刷新率等重新绘制小部件。

对于高级交互，Qt 使用基于 signal/slot 的类似模式机制:

Observer pattern is used everywhere in GUI applications and often leads to some boilerplate code. Qt was created with the idea of removing this boilerplate code and providing a nice and clean syntax, and the signal and slots mechanism is the answer.