QT错误集锦~
这篇是在10年测试QT过程中遇到的问题：
1、中文显示问题：
#include <QApplication>
#include <QLabel>
#include <QTextCodec>
int main(int argc, char* argv[])
{
QApplication app(argc,argv);
QTextCodec::setCodecForTr(QTextCodec::codecForName("UTF-8"));
QLabel *label = new QLabel(tr("这里是中文"));
label->Show();
return app.exec();
}
编译代码，得到的错误是： 'tr'在此作用域中尚未声明。
昨天为什么没有出现这种错误呢？因为昨天的代码是从qt creator生成的MainWindow中挑出来的，tr被声明为QObject的一个static方法，因此在MainWindow中使用tr不会有问题。
把上面的
QLabel *label=new QLabel(tr("这里是中文"));
改为
QLabel *label=new QLabel(QObject::tr("这里是中文"));
2、中文问题：
使用sqlite数据库显示乱码的问题
//main.cpp
#include <QtGui>
#include <QtCore/QTextCodec>
#include <QSqlTableModel>
#include <QTableView>
#include <QHeaderView>
#include <QSqlRecord>
#include <QtGui/QLabel>
#include <QString>
#include <QVariant>
#include "connection.h"
#include "sql.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QTextCodec::setCodecForTr(QTextCodec::codecForName("GBK"));
//创建数据库连接
if (!createConnection())
return 1;
//创建学生信息表
createTables();
//初始添加数据
addData();
enum{
Student_Id = 0,
Student_Schnum = 1,
Student_Name = 2,
Student_Sex = 3,
Student_Nation = 4
};
QSqlTableModel *model = new QSqlTableModel();
model->setTable("student");
model->setSort(Student_Schnum, Qt::AscendingOrder);
model->setHeaderData(Student_Schnum, Qt::Horizontal, QObject::tr("学号"));
model->setHeaderData(Student_Name, Qt::Horizontal, QObject::tr("姓名"));
model->setHeaderData(Student_Sex, Qt::Horizontal, QObject::tr("性别"));
model->setHeaderData(Student_Nation, Qt::Horizontal, QObject::tr("民族"));
model->select();
QTableView *view = new QTableView;
view->setModel(model);
view->setSelectionMode(QAbstractItemView::SingleSelection);
view->setSelectionBehavior(QAbstractItemView::SelectRows);
view->setColumnHidden(Student_Id, true);
view->resizeColumnsToContents();
view->setEditTriggers(QAbstractItemView::NoEditTriggers);
QHeaderView *header = view->horizontalHeader();
header->setStretchLastSection(true);
view->show();
return a.exec();
}
//connection.h
#ifndef CONNECTION_H
#define CONNECTION_H
#include <QMessageBox>
#include <QSqlDatabase>
#include <QSqlError>
#include <QSqlDriver>
inline bool createConnection()
{
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("sim.dat");
if (!db.open()) {
QMessageBox::warning(0, QObject::tr("Database Error"),
db.lastError().text());
return false;
}
return true;
}
#endif // CONNECTION_H
//sql.h
#include <QSqlQuery>
#ifndef SQL_H
#define SQL_H
inline void createTables()
{
QSqlQuery query;
query.exec("CREATE TABLE student ("
"id INTEGER PRIMARY KEY, "
"schnum INTEGER NOT NULL, "
"name VARCHAR(40) NOT NULL, "
"sex VARCHAR(4) NOT NULL, "
"nation VARCHAR(10) NOT NULL)");
}
inline void addData(){
QSqlQuery query;
for(int i =0;i<100;i++){
query.exec("INSERT INTO student (schnum, name, sex, nation) VALUES (2614103, '天残脚,'男', '汉族')");
}
}
#endif // SQL_H
上网查了许多无果，后来在阅读一篇技术文章中无意发现，原来在插入数据语句若有中文必须先QObject::tr()一番，即进行编码，
将Sql.h中query.exec("INSERT INTO student (schnum, name, sex, nation) VALUES (2614103, '天残脚,'男', '汉族')");改为如下query.exec(QObject::tr("INSERT INTO student (schnum, name, sex, nation) VALUES (2614103, '天残脚,'男', '汉族')"));
结果在显示中都能得正确显示。
注意，如果语句 QTextCodec::setCodecForTr(QTextCodec::codecForName("GBK"));中的编码改为utf-8则会显示乱码。
QLabel *label = new QLabel( tr("中文标签") );
mingw32-make: *** No rule to make target `http://www.cnblogs.com/http://www.cnblogs.com/Qt/4.3.3/mkspecs/default/qmake.conf', needed by `makefile'. Stop.
make[2]: Entering directory `/home/lzy/tps2/rplan/super'
make[2]: *** No rule to make target `/home/lzy/qt/qt-3.3.2/mkspecs/default/qmake.conf', needed by `Makefile'. Stop.
make[2]: Leaving directory `/home/lzy/tps2/rplan/super'
本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/wangya216/archive/2009/06/08/4252689.aspx
5、mingw32\bin\ld.exe: cannot find -lqtmaind错误
这个错误是缺少某些库，将mingw重新下载安装即可。
6、编译时可能会遇到如下错误：previous declaration 'long int InterlockedIncrement(long int*)' here
此为qt的bug需要修改源代码 （Qt\4.4.3\src\corelib\arch\qatomic_windows.h），
原文件如下：
Solution:
(1) Qt\4.4.3\src\corelib\arch\qatomic_windows.h:
#if !(defined Q_CC_BOR) || (__BORLANDC__ < 0x560)
extern "C" {
__declspec(dllimport) long __stdcall InterlockedCompareExchange(long *, long, long);
__declspec(dllimport) long __stdcall InterlockedIncrement(long *);
__declspec(dllimport) long __stdcall InterlockedDecrement(long *); __declspec(dllimport) long __stdcall InterlockedExchange(long *, long);
__declspec(dllimport) long __stdcall InterlockedExchangeAdd(long *, long);
}
#else
extern "C" {
__declspec(dllimport) long __stdcall InterlockedCompareExchange(long volatile*, long, long);
__declspec(dllimport) long __stdcall InterlockedIncrement(long volatile*);
__declspec(dllimport) long __stdcall InterlockedDecrement(long volatile*);
__declspec(dllimport) long __stdcall InterlockedExchange(long volatile*, long);
__declspec(dllimport) long __stdcall InterlockedExchangeAdd(long volatile*, long);
}
#endif
you will see above code in Qt\4.4.3\src\corelib\arch\qatomic_windows.h: file. I modified like below and it works.
/*#if !(defined Q_CC_BOR) || (__BORLANDC__ < 0x560)
extern "C" {
__declspec(dllimport) long __stdcall InterlockedCompareExchange(long *, long, long);
__declspec(dllimport) long __stdcall InterlockedIncrement(long *);
__declspec(dllimport) long __stdcall InterlockedDecrement(long *); __declspec(dllimport) long __stdcall InterlockedExchange(long *, long);
__declspec(dllimport) long __stdcall InterlockedExchangeAdd(long *, long);
}
#else */
extern "C" {
__declspec(dllimport) long __stdcall InterlockedCompareExchange(long volatile*, long, long);
__declspec(dllimport) long __stdcall InterlockedIncrement(long volatile*);
__declspec(dllimport) long __stdcall InterlockedDecrement(long volatile*);
__declspec(dllimport) long __stdcall InterlockedExchange(long volatile*, long);
__declspec(dllimport) long __stdcall InterlockedExchangeAdd(long volatile*, long);
}
// #endif
7、编译错误，显示 can not find -lqtmaind。
这是qt的debug库，安装完成后需要再自己编译这个库。在Qt的开始菜单中，你可以找到一个程序 Qt 4.4.0 (Build Debug Libraries)，运行这个程序就能编译Qt的Debug库了。
