CheckBox QML Type

Check button that can be toggled on or off. 更多...

导入语句：	import QtQuick.Controls 2.5
Since:	Qt 5.7
继承：	AbstractButton

所有成员列表，包括继承成员

特性

checkState : enumeration
nextCheckState : function
tristate : bool

详细描述

CheckBox presents an option button that can be toggled on (checked) or off (unchecked). Check boxes are typically used to select one or more options from a set of options. For larger sets of options, such as those in a list, consider using CheckDelegate 代替。

CheckBox inherits its API from AbstractButton . For instance, the state of the checkbox can be set with the checked 特性。

In addition to the checked and unchecked states, there is a third state: partially checked. The partially checked state can be enabled using the tristate property. This state indicates that the regular checked/unchecked state can not be determined; generally because of other states that affect the checkbox. This state is useful when several child nodes are selected in a treeview, for example.

ColumnLayout {
    CheckBox {
        checked: true
        text: qsTr("First")
    }
    CheckBox {
        text: qsTr("Second")
    }
    CheckBox {
        checked: true
        text: qsTr("Third")
    }
}

Hierarchical checkbox groups can be managed with a non-exclusive ButtonGroup .

The following example illustrates how the combined check state of children can be bound to the check state of the parent checkbox:

Column {
    ButtonGroup {
        id: childGroup
        exclusive: false
        checkState: parentBox.checkState
    }
    CheckBox {
        id: parentBox
        text: qsTr("Parent")
        checkState: childGroup.checkState
    }
    CheckBox {
        checked: true
        text: qsTr("Child 1")
        leftPadding: indicator.width
        ButtonGroup.group: childGroup
    }
    CheckBox {
        text: qsTr("Child 2")
        leftPadding: indicator.width
        ButtonGroup.group: childGroup
    }
}

另请参阅 Customizing CheckBox , ButtonGroup ，和按钮控件 .

特性文档编制

checkState : enumeration

This property holds the check state of the checkbox.

Available states:

常量	描述
`Qt.Unchecked`	The checkbox is unchecked.
`Qt.PartiallyChecked`	The checkbox is partially checked. This state is only used when tristate is enabled.
`Qt.Checked`	The checkbox is checked.

另请参阅 tristate and checked .

nextCheckState : function

This property holds a callback function that is called to determine the next check state whenever the checkbox is interactively toggled by the user via touch, mouse, or keyboard.

By default, a normal checkbox cycles between Qt.Unchecked and Qt.Checked states, and a tri-state checkbox cycles between Qt.Unchecked , Qt.PartiallyChecked ，和 Qt.Checked 状态。

nextCheckState callback function can override the default behavior. The following example implements a tri-state checkbox that can present a partially checked state depending on external conditions, but never cycles to the partially checked state when interactively toggled by the user.

CheckBox {
    tristate: true
    checkState: allChildrenChecked ? Qt.Checked :
                   anyChildChecked ? Qt.PartiallyChecked : Qt.Unchecked
    nextCheckState: function() {
        if (checkState === Qt.Checked)
            return Qt.Unchecked
        else
            return Qt.Checked
    }
}

This property was introduced in QtQuick.Controls 2.4 (Qt 5.11).

tristate : bool

This property holds whether the checkbox is a tri-state checkbox.

In the animation below, the first checkbox is tri-state:

默认为 false , i.e., the checkbox has only two states.