Qt 5 的新功能

In today's world, location and maps information is more widely used, be it to look up nearby restaurants or plan commute to the office. With Qt, it is now possible to cater to these use cases by consuming map data provided by the third-party vendors. The Qt Location module provides the APIs and the necessary backend to fetch map data from some of the popular third-party mapping solutions. Here is a snapshot of the demo application running on Android, presenting OpenStreetMap data from www.mapquest.com .

Mapviewer 范例屏幕截图

Qt Platform Abstraction

The windowing system dependent parts of Qt have been completely rewritten for Qt 5, based on the Qt Platform Abstraction, a plugin architecture which allows Qt to dynamically load a windowing system integration based on what system it is running on. This gives several benefits:

• Centralize the windowing system integration codebase into classes shared for all platforms.
• Simplify the work required when porting Qt to new platforms.
• Remove the windowing system dependency from Qt, making it possible to have the same Qt binaries run against multiple windowing systems. For instance, the Qt Linux binaries can run against both X11 and Wayland.

新连接句法

In addition to the still available well known way to connect signals and slots, new overloads of QObject::connect have been added allowing you to connect signals and slot using pointer to member functions:

QObject::connect(sender, &Sender::valueChanged, receiver, &Receiver::updateValue);
														

The new syntax provides compile time checking of the compatibility between signals and slots, automatic conversion of the arguments if there is an implicit cast between the types, and solve many problems occurring because of typedef or namespaces.

Additionally, if your compiler supports C++11 lambdas, you can even connect directly to a lambda function.

connect(sender, &QObject::destroyed, [=](){ this->m_objects.remove(sender); });
														

For a detailed comparison with the original string-based syntax, see 基于字符串的连接和基于函子的连接之间的差异 .

连接和网络

Qt 5 provides better support for IPv6 and dual mode networks. Most applications using host names and network layer transparent protocols can now gain IPv6 support transparently. Such applications can also choose to receive both IPv4 and IPv6 connections or bind to only one of the two connection types. In the case of outgoing HTTP connections using QNetworkAccessManager , both IPv4 and IPv6 connections are attempted in parallel, and the one that succeeds first is used. This is useful in environments where one of the two types has limited connectivity.

Qt 5 also provides better ways to handle TCP socket-based connections and SSL certificates. This means developers can now:

• bind a TCP socket to an IP address before connecting,
• verify an SSL certificate chain,
• and access legacy systems.

Stricter client authentication is one of the primary concerns for many applications handling confidential or critical data. The opaque Private Keys support in Qt 5 enables applications to read private keys from devices such as PKCS#11 dongles for stricter client authentication. The qsslkey example illustrates reading private keys from a device.

扩展连接

The connectivity options are endless with Qt 5. The two new modules, Qt Bluetooth and Qt NFC , enable developers to add support for sophisticated ways to connect and share information in their application.

JSON 支持

Qt applications that use simple data structures to store small amount of data, can now choose to use JSON documents over the complex database backends that need necessary drivers or plugins to access data. The fact that JSON is a text-based open standard derived from JavaScript, makes it the obvious choice for QML applications as well.

The Qt Core provides a set of classes to enable parsing and generating JSON documents. These classes also allow you to convert between an in-memory binary representation of JSON to a standard textual JSON format. The goal is to make common operations on JSON faster.

用户输入

Qt 4 already had support for handling multi-point touch input in C++. Qt 5 extends this support to include Qt Quick, covering all the information about the touch points, including the touch position, pressure, and velocity.

The mouse event handling in Qt 5 has been improved from its predecessor. Applications have more control to handle mouse events in Qt Quick. The mouse area in a QML document can propagate the mouse wheel and click events and also ignore propagated events.

Besides this, Qt 5 adds support for more mouse buttons on platforms where this is supported. This comes in handy for gaming applications developed using Qt.

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