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This article mainly explains "case Analysis of Qt Development skills". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Now let the editor to take you to learn the "Qt development skills case analysis" bar!

In some http post data, if the & string concatenation is used to send data and parse garbled codes in Chinese, it is necessary to transcode the Chinese language into URL.

QString content = "Test Chinese"; QString note = content.toUtf8 () .toPercentEncoding ()

Qt does not support large resource files by default. For example, if a font file is added, it needs to be opened by pro file. CONFIG + = resources_big

After inheriting QWidget in Qt, the stylesheet does not work, and there are three solutions. Method one is highly recommended. Method 1: set the properties this- > setAttribute (Qt::WA_StyledBackground, true); method 2: inherit QFrame, because QFrame comes with the paintEvent function has been implemented, when using the stylesheet will be parsed and drawn. Method 3: when you re-implement the paintEvent function of QWidget, use QStylePainter to draw.

Void myclass::paintEvent (QPaintEvent *) {QStyleOption o; o.initFrom (this); QPainter p (this); style ()-> drawPrimitive (QStyle::PE_Widget, & o, & p, this);}

Sometimes add a spring to the interface, need to dynamically change the tension strategy corresponding to the spring, the corresponding method is changeSize, many people will choose to use the beginning of set to find, can not find.

In the process of using QFile, it is not recommended to frequently open the file to write and then close the file. For example, interval 5ms output log, IO performance bottleneck is very large. In this case, it is recommended to open the file first and not close it. Wait for the appropriate time, such as in the destructor or when the date changes and needs to re-change the log file. Otherwise, a large number of open and closed files in a short period of time will be very stuck, the larger the file, the more stuck.

In many network applications, a custom heartbeat packet is required to maintain the connection, otherwise the power is cut off or the program is illegally closed, which cannot be recognized by the other party and requires timeout detection, but some programs do not provide heartbeat protocol, so you need to enable the system-level activating program. This method is suitable for TCP connections.

Int fd = tcpSocket- > socketDescriptor (); int keepAlive = 1; / enable keepalive attribute, default value: 0 (off) int keepIdle = 5; / / if there is no data interaction within 5 seconds, probe is performed, default value: 7200 (s) int keepInterval = 2; / / probe packet interval is 2 seconds, default value: 75 (s) int keepCount = 2 / / detect the number of retries. The connection is considered invalid if all timeouts occur. Default values: 9 (times) setsockopt (fd, SOL_SOCKET, SO_KEEPALIVE, (void *) & keepAlive, sizeof (keepAlive)); setsockopt (fd, SOL_TCP, TCP_KEEPIDLE, (void *) & keepIdle, sizeof (keepIdle)); setsockopt (fd, SOL_TCP, TCP_KEEPINTVL, (void *) & keepInterval, sizeof (keepInterval)) Setsockopt (fd, SOL_TCP, TCP_KEEPCNT, (void *) & keepCount, sizeof (keepCount))

If the program is packaged, the pop-up prompt This application failed to start because it could not find or load the Qt platform plugin is usually caused by the fact that the platforms plug-in directory is not packaged or mispackaged.

It is not recommended to include Chinese in tr, although the new version of Qt supports translation from Chinese to other languages, it is very irregular, and I don't know who taught TMD. The original intention of tr is to include English, and then translate to other languages such as Chinese. now a large number of beginners abuse tr, if there is no need for translation, disabling tr,tr requires overhead, Qt will think by default that he needs translation and will undergo extra special treatment.

Many people Qt and Qt Creator silly do not know, often ask Qt what version of the result to send a version of Qt Creator, Qt Creator is the use of Qt to write the integrated development environment IDE, and the first in the universe Visual Studio, he can be a msvc compiler (WIN corresponding to the Qt integrated installation environment comes with Qt Cerator is msvc), can also be mingw compiled, can also be gcc. If it is a custom control plug-in, it needs to be integrated into Qt Creator. You must ensure that the compiler and Qt version corresponding to the plug-in's dynamic library files (such as dll or so files) and the number of bits are exactly the same as the Qt Creator version, otherwise it is unlikely to be integrated. In particular, it is important to note that the Qt and Qt Creator versions in the Qt integrated environment installation package may not be exactly the same, and you must keep your eyes open and see clearly, some of them are exactly the same.

If there are more than two codes with the same processing, it is recommended to write them separately as functions. The code should be as standard and concise as possible, for example, if (a = 123) should be written as if (123 = = a), with the value in front, and for example, if (ok = = true) should be written as if (ok), if (ok = = false) should be written as if (! ok), and so on.

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