Among the elements of the user interface window form, selection or data entry fields are of particular importance. The processing of the set values must often be instantaneous. Therefore, the developer needs to receive information for any change in the windows. In different situations, when reading a field value, you need to consider the specific data type and scope of the form element.
Instructions
Step 1
When developing applications using the Qt programming library, window forms are usually created from widgets (QWidget class) or dialogs (QDialog). Elements for selection or data entry are added to objects of the specified classes and are visually located on a standard or dialog box.
Step 2
Use the QComboBox class to work with the dropdown list. Its visible working field can be active for data entry or locked. If the user is able to enter a value in the field, then you can get it by referring to the list object. Example code: QComboBox m_comb; QString result; result = m_comb.currentText (); Here, the m_comb object using the currentText () method returns the current value of the top field, and it can be either entered or selected in the drop-down list. The string variable result contains the value from the visible working field of the combobox.
Step 3
However, the entered data type can also be numeric. To convert string values to the required type, perform one of the following operations: double resD = result.toDouble (); float resF = result.toFloat (); int resI = result.toInt (); Here, the resulting field value will be stored in the resD variable, but already in a double, in resF - a float value, and in resI - an int integer value.
Step 4
When using the QLineEdit single line text editor as a data entry element, grab the information you need with the following entry: result = m_edit.text (). Here, the m_edit object, using the text () function, returns the string value entered by the user into the field.
Step 5
A QListBox element can perform a similar function in a windowed form, access to the entered data for this object is also similar to the previously specified one: m_list.currentText ().
Step 6
When accessing all instances of the described classes, you must have the appropriate access rights, since calling private methods and objects is impossible from third-party functions. The considered methods for getting the field value have an open status.
