c131a83f42
- \image --> \borderedimage - update screenshot if required Change-Id: I0318b1df67154b70c061da7cbd509b8d5337b311 Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>
192 lines
7.4 KiB
Plaintext
192 lines
7.4 KiB
Plaintext
/****************************************************************************
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**
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** Copyright (C) 2016 The Qt Company Ltd.
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****************************************************************************/
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/*!
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\example widgets/spinboxes
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\title Spin Boxes Example
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\ingroup examples-widgets
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\brief The Spin Boxes example shows how to use the many different types of
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spin boxes available in Qt, from a simple QSpinBox widget to more complex
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editors like the QDateTimeEdit widget.
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\borderedimage spinboxes-example.png
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The example consists of a single \c Window class that is used to display the
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different spin box-based widgets available with Qt.
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\section1 Window Class Definition
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The \c Window class inherits QWidget and contains two slots that are used
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to provide interactive features:
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\snippet widgets/spinboxes/window.h 0
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The private functions are used to set up each type of spin box in the window.
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We use member variables to keep track of various widgets so that they can
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be reconfigured when required.
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\section1 Window Class Implementation
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The constructor simply calls private functions to set up the different types
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of spin box used in the example, and places each group in a layout:
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\snippet widgets/spinboxes/window.cpp 0
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We use the layout to manage the arrangement of the window's child widgets,
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and change the window title.
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The \c createSpinBoxes() function constructs a QGroupBox and places three
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QSpinBox widgets inside it with descriptive labels to indicate the types of
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input they expect.
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\snippet widgets/spinboxes/window.cpp 1
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The first spin box shows the simplest way to use QSpinBox. It accepts values
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from -20 to 20, the current value can be increased or decreased by 1 with
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either the arrow buttons or \uicontrol{Up} and \uicontrol{Down} keys, and the default
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value is 0.
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The second spin box uses a larger step size and displays a suffix to
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provide more information about the type of data the number represents:
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\snippet widgets/spinboxes/window.cpp 2
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This spin box also displays a
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\l{QAbstractSpinBox::specialValueText}{special value} instead of the minimum
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value defined for it. This means that it will never show \uicontrol{0%}, but will
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display \uicontrol{Automatic} when the minimum value is selected.
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The third spin box shows how a prefix can be used:
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\snippet widgets/spinboxes/window.cpp 4
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For simplicity, we show a spin box with a prefix and no suffix. It is also
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possible to use both at the same time.
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\snippet widgets/spinboxes/window.cpp 5
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The rest of the function sets up a layout for the group box and places each
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of the widgets inside it.
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The \c createDateTimeEdits() function constructs another group box with a
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selection of spin boxes used for editing dates and times.
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\snippet widgets/spinboxes/window.cpp 6
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The first spin box is a QDateEdit widget that is able to accept dates
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within a given range specified using QDate values. The arrow buttons and
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\uicontrol{Up} and \uicontrol{Down} keys can be used to increase and decrease the
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values for year, month, and day when the cursor is in the relevant section.
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The second spin box is a QTimeEdit widget:
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\snippet widgets/spinboxes/window.cpp 7
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Acceptable values for the time are defined using QTime values.
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The third spin box is a QDateTimeEdit widget that can display both date and
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time values, and we place a label above it to indicate the range of allowed
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times for a meeting. These widgets will be updated when the user changes a
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format string.
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\snippet widgets/spinboxes/window.cpp 8
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The format string used for the date time editor, which is also shown in the
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string displayed by the label, is chosen from a set of strings in a combobox:
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\snippet widgets/spinboxes/window.cpp 9
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\codeline
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\snippet widgets/spinboxes/window.cpp 10
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A signal from this combobox is connected to a slot in the \c Window class
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(shown later).
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\snippet widgets/spinboxes/window.cpp 11
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Each child widget of the group box in placed in a layout.
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The \c setFormatString() slot is called whenever the user selects a new
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format string in the combobox. The display format for the QDateTimeEdit
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widget is set using the raw string passed by the signal:
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\snippet widgets/spinboxes/window.cpp 12
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Depending on the visible sections in the widget, we set a new date or time
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range, and update the associated label to provide relevant information for
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the user:
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\snippet widgets/spinboxes/window.cpp 13
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When the format string is changed, there will be an appropriate label and
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entry widget for dates, times, or both types of input.
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The \c createDoubleSpinBoxes() function constructs three spin boxes that are
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used to input double-precision floating point numbers:
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\snippet widgets/spinboxes/window.cpp 14
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Before the QDoubleSpinBox widgets are constructed, we create a spin box to
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control how many decimal places they show. By default, only two decimal places
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are shown in the following spin boxes, each of which is the equivalent of a
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spin box in the group created by the \c createSpinBoxes() function.
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The first double spin box shows a basic double-precision spin box with the
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same range, step size, and default value as the first spin box in the
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\c createSpinBoxes() function:
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\snippet widgets/spinboxes/window.cpp 15
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However, this spin box also allows non-integer values to be entered.
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The second spin box displays a suffix and shows a special value instead
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of the minimum value:
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\snippet widgets/spinboxes/window.cpp 16
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The third spin box displays a prefix instead of a suffix:
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\snippet widgets/spinboxes/window.cpp 17
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We connect the QSpinBox widget that specifies the precision to a slot in
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the \c Window class.
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\snippet widgets/spinboxes/window.cpp 18
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The rest of the function places each of the widgets into a layout for the
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group box.
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The \c changePrecision() slot is called when the user changes the value in
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the precision spin box:
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\snippet widgets/spinboxes/window.cpp 19
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This function simply uses the integer supplied by the signal to specify the
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number of decimal places in each of the QDoubleSpinBox widgets. Each one
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of these will be updated automatically when their
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\l{QDoubleSpinBox::decimals}{decimals} property is changed.
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*/
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