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Overview

Signal and slot mechanism is the core mechanism of QT. If you want to be proficient in QT programming, you must have some understanding of signal and slot. Signal and slot is a kind of advanced interface, which is applied to the communication between objects. It is the core feature of QT and the important place that distinguishes QT from other toolkits. Signals and slots are a communication mechanism defined by QT, which is independent of the standard Cmax Candle + language, so in order to deal with signals and slots correctly, we must rely on a QT tool called moc (Meta Object Compiler), which is a C++ preprocessor that automatically generates additional code for high-level event processing.

New project

After the project is completed, we will add a Push Button to the UI interface.

Click the second button above or press F4 to enter the signal and slot editing interface

Then click PushButton to drag

When you release it, the configuration link will pop up. Now there is only a list on the left. We click on the lower left corner to show the signals and slots inherited from QWidget.

Check click () and close ()

Interface after editing

You will see that it is associated with the close () event of the form

Press the first button or F3 to exit the signal and slot editing interface and return to the form interface.

After running, clicking the button will close the current form.

Then we add a Dial control and a Progress Bar control

Set the signal and slot of the two controls to associate this

Configure and connect the valueChanged (int) event in the Dial control to setValue (int)

When the program runs, we turn the Dial control on the left and the ProgressBar on the right changes accordingly.

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