这个问题,教程C++ GUI Programming with Qt 4, Second Edition说得很清楚。
Click Edit|Edit Signals/Slots to enter Qt Designer's connection mode. Connections are represented by blue arrows between the form's widgets, as shown in Figure 2.15, and they are also listed in Qt Designer's signal/slot editor window. To establish a connection between two widgets, click the sender widget and drag the red arrow line to the receiver widget, then release. This pops up a dialog that allows you to choose the signal and the slot to connect.
跟着它走几个章节,许多基本东西都会了。