内容

• 公共类型
• 公共函数
• 静态公共成员
• 相关非成员
• 详细描述

QLowEnergyCharacteristic Class

The QLowEnergyCharacteristic class stores information about a Bluetooth Low Energy service characteristic. 更多...

头：	#include <QLowEnergyCharacteristic>
qmake:	QT += bluetooth
Since:	Qt 5.4

• 所有成员列表，包括继承成员

公共类型

enum	PropertyType { Unknown, Broadcasting, Read, WriteNoResponse, Write, …, ExtendedProperty }
flags	PropertyTypes

公共函数

	QLowEnergyCharacteristic (const QLowEnergyCharacteristic & other )
	QLowEnergyCharacteristic ()
QLowEnergyCharacteristic &	operator= (const QLowEnergyCharacteristic & other )
	~QLowEnergyCharacteristic ()
QLowEnergyDescriptor	clientCharacteristicConfiguration () const
QLowEnergyDescriptor	descriptor (const QBluetoothUuid & uuid ) const
QList<QLowEnergyDescriptor>	descriptors () const
bool	isValid () const
QString	name () const
QLowEnergyCharacteristic::PropertyTypes	properties () const
QBluetoothUuid	uuid () const
QByteArray	value () const

静态公共成员

const QByteArray	CCCDDisable
const QByteArray	CCCDEnableIndication
const QByteArray	CCCDEnableNotification

相关非成员

bool	operator!= (const QLowEnergyCharacteristic & a , const QLowEnergyCharacteristic & b )
bool	operator== (const QLowEnergyCharacteristic & a , const QLowEnergyCharacteristic & b )

详细描述

QLowEnergyCharacteristic provides information about a Bluetooth Low Energy service characteristic's name (), uuid (), value (), properties ()，和 descriptors (). To obtain the characteristic's specification and information, it is necessary to connect to the device using the QLowEnergyService and QLowEnergyController 类。

The characteristic value may be written via the QLowEnergyService instance that manages the service to which this characteristic belongs. The QLowEnergyService::writeCharacteristic () function writes the new value. The QLowEnergyService::characteristicWritten () signal is emitted upon success. The value () of this object is automatically updated accordingly.

Characteristics may contain none, one or more descriptors. They can be individually retrieved using the descriptor () 函数。 descriptors () function returns all descriptors as a list. The general purpose of a descriptor is to add contextual information to the characteristic. For example, the descriptor might provide format or range information specifying how the characteristic's value is to be interpreted.

另请参阅 QLowEnergyService and QLowEnergyDescriptor .

成员类型文档编制

enum QLowEnergyCharacteristic:: PropertyType
flags QLowEnergyCharacteristic:: PropertyTypes

This enum describes the properties of a characteristic.

常量	值	描述
QLowEnergyCharacteristic::Unknown	0x00	The type is not known.
QLowEnergyCharacteristic::Broadcasting	0x01	Allow for the broadcasting of Generic Attributes (GATT) characteristic values.
QLowEnergyCharacteristic::Read	0x02	Allow the characteristic values to be read.
QLowEnergyCharacteristic::WriteNoResponse	0x04	Allow characteristic values without responses to be written.
QLowEnergyCharacteristic::Write	0x08	Allow for characteristic values to be written.
QLowEnergyCharacteristic::Notify	0x10	Permits notification of characteristic values.
QLowEnergyCharacteristic::Indicate	0x20	Permits indications of characteristic values.
QLowEnergyCharacteristic::WriteSigned	0x40	Permits signed writes of the GATT characteristic values.
QLowEnergyCharacteristic::ExtendedProperty	0x80	Additional characteristic properties are defined in the characteristic's extended properties descriptor.

The PropertyTypes type is a typedef for QFlags <PropertyType>. It stores an OR combination of PropertyType values.

另请参阅 properties ().

成员函数文档编制

QLowEnergyCharacteristic:: QLowEnergyCharacteristic (const QLowEnergyCharacteristic & other )

Construct a new QLowEnergyCharacteristic that is a copy of other .

The two copies continue to share the same underlying data which does not detach upon write.

QLowEnergyCharacteristic:: QLowEnergyCharacteristic ()

Construct a new QLowEnergyCharacteristic. A default-constructed instance of this class is always invalid.

另请参阅 isValid ().

QLowEnergyCharacteristic &QLowEnergyCharacteristic:: operator= (const QLowEnergyCharacteristic & other )

制作副本为 other 并将其赋值给此 QLowEnergyCharacteristic object. The two copies continue to share the same service and controller details.

QLowEnergyCharacteristic:: ~QLowEnergyCharacteristic ()

销毁 QLowEnergyCharacteristic 对象。

[since 6.2] QLowEnergyDescriptor QLowEnergyCharacteristic:: clientCharacteristicConfiguration () const

Returns the Client Characteristic Configuration Descriptor or an invalid QLowEnergyDescriptor instance if no Client Characteristic Configuration Descriptor exists.

BTLE characteristics can support notifications and/or indications. In both cases, the peripheral will inform the central on each change of the characteristic's value. In the BTLE attribute protocol, notification messages are not confirmed by the central, while indications are confirmed. Notifications are considered faster, but unreliable, while indications are slower and more reliable.

If a characteristic supports notification or indication, these can be enabled by writing special bit patterns to the Client Characteristic Configuration Descriptor. For convenience, these bit patterns are provided as QLowEnergyCharacteristic::CCCDDisable , QLowEnergyCharacteristic::CCCDEnableNotification ，和 QLowEnergyCharacteristic::CCCDEnableIndication .

Enabling e.g. notification for a characteristic named mycharacteristic in a service called myservice could be done using the following code.

auto cccd = mycharacteristic.clientCharacteristicConfiguration();
if (!cccd.isValid()) {
    // your error handling
    return error;
}
myservice->writeDescriptor(cccd, QLowEnergyCharacteristic::CCCDEnableNotification);
					

注意： 调用 characteristic.clientCharacteristicConfiguration() 相当于调用 characteristic.descriptor(QBluetoothUuid::DescriptorType::ClientCharacteristicConfiguration) .

该函数在 Qt 6.2 引入。

另请参阅 descriptor ().

QLowEnergyDescriptor QLowEnergyCharacteristic:: descriptor (const QBluetoothUuid & uuid ) const

Returns the descriptor for uuid or an invalid QLowEnergyDescriptor 实例。

另请参阅 descriptors ().

QList < QLowEnergyDescriptor > QLowEnergyCharacteristic:: descriptors () const

Returns the list of descriptors belonging to this characteristic; otherwise an empty list.

另请参阅 descriptor ().

bool QLowEnergyCharacteristic:: isValid () const

返回 true 若 QLowEnergyCharacteristic object is valid, otherwise returns false .

An invalid characteristic object is not associated with any service (default-constructed) or the associated service is no longer valid due to a disconnect from the underlying Bluetooth Low Energy device, for example. Once the object is invalid it cannot become valid anymore.

注意： 若 QLowEnergyCharacteristic instance turns invalid due to a disconnect from the underlying device, the information encapsulated by the current instance remains as it was at the time of the disconnect. Therefore it can be retrieved after the disconnect event.

QString QLowEnergyCharacteristic:: name () const

Returns the human-readable name of the characteristic.

The name is based on the characteristic's uuid () which must have been standardized. The complete list of characteristic types can be found under Bluetooth.org Characteristics .

The returned string is empty if the uuid () is unknown.

另请参阅 QBluetoothUuid::characteristicToString ().

QLowEnergyCharacteristic::PropertyTypes QLowEnergyCharacteristic:: properties () const

Returns the properties of the characteristic.

The properties define the access permissions for the characteristic.

QBluetoothUuid QLowEnergyCharacteristic:: uuid () const

Returns the UUID of the characteristic if isValid () 返回 true ; otherwise a null UUID.

QByteArray QLowEnergyCharacteristic:: value () const

Returns the cached value of the characteristic.

If the characteristic's properties () permit writing of new values, the value can be updated using QLowEnergyService::writeCharacteristic ().

The cache is updated during the associated service's detail discovery , a successful read / write operation or when an update notification is received.

返回的 QByteArray always remains empty if the characteristic does not have the read permission . In such cases only the QLowEnergyService::characteristicChanged () 或 QLowEnergyService::characteristicWritten () may provice information about the value of this characteristic.

成员变量文档编制

[since 6.2] const QByteArray QLowEnergyCharacteristic:: CCCDDisable

Bit pattern to write into Client Characteristic Configuration Descriptor to disable both notification and indication.

This documentation was introduced in Qt 6.2.

另请参阅 QLowEnergyCharacteristic::clientCharacteristicConfiguration .

[since 6.2] const QByteArray QLowEnergyCharacteristic:: CCCDEnableIndication

Bit pattern to write into Client Characteristic Configuration Descriptor to enable indication.

This documentation was introduced in Qt 6.2.

另请参阅 QLowEnergyCharacteristic::clientCharacteristicConfiguration .

[since 6.2] const QByteArray QLowEnergyCharacteristic:: CCCDEnableNotification

Bit pattern to write into Client Characteristic Configuration Descriptor to enable notification.

This documentation was introduced in Qt 6.2.

另请参阅 QLowEnergyCharacteristic::clientCharacteristicConfiguration .

相关非成员

bool operator!= (const QLowEnergyCharacteristic & a , const QLowEnergyCharacteristic & b )

返回 true if a and b are not equal; otherwise false .

Two QLowEnergyCharcteristic instances are considered to be equal if they refer to the same characteristic on the same remote Bluetooth Low Energy device or both instances have been default-constructed.

bool operator== (const QLowEnergyCharacteristic & a , const QLowEnergyCharacteristic & b )

返回 true if a 等于 b , otherwise false .

Two QLowEnergyCharacteristic instances are considered to be equal if they refer to the same characteristic on the same remote Bluetooth Low Energy device or both instances have been default-constructed.