這篇是在10年測試QT過程中遇到的問題：
1、中文顯示問題：
#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("這裏是中文"));
label->Show();
return app.exec();
}
編譯代碼，得到的錯誤是： 'tr'在此作用域中尚未聲明。
昨天爲什麼沒有出現這種錯誤呢？因爲昨天的代碼是從qt creator生成的MainWindow中挑出來的，tr被聲明爲QObject的一個static方法，因此在MainWindow中使用tr不會有問題。
把上面的
QLabel *label=new QLabel(tr("這裏是中文"));
改爲
QLabel *label=new QLabel(QObject::tr("這裏是中文"));
2、中文問題：
使用sqlite數據庫顯示亂碼的問題
//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"));
//創建數據庫連接
if (!createConnection())
return 1;
//創建學生信息表
createTables();
//初始添加數據
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("學號"));
model->setHeaderData(Student_Name, Qt::Horizontal, QObject::tr("姓名"));
model->setHeaderData(Student_Sex, Qt::Horizontal, QObject::tr("性別"));
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, '天殘腳,'男', '漢族')");
}
}
#endif // SQL_H
上網查了許多無果，後來在閱讀一篇技術文章中無意發現，原來在插入數據語句若有中文必須先QObject::tr()一番，即進行編碼，
將Sql.h中query.exec("INSERT INTO student (schnum, name, sex, nation) VALUES (2614103, '天殘腳,'男', '漢族')");改爲如下query.exec(QObject::tr("INSERT INTO student (schnum, name, sex, nation) VALUES (2614103, '天殘腳,'男', '漢族')"));
結果在顯示中都能得正確顯示。
注意，如果語句 QTextCodec::setCodecForTr(QTextCodec::codecForName("GBK"));中的編碼改爲utf-8則會顯示亂碼。
QLabel *label = new QLabel( tr("中文標籤") );
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'
本文來自CSDN博客，轉載請標明出處：http://blog.csdn.net/wangya216/archive/2009/06/08/4252689.aspx
5、mingw32\bin\ld.exe: cannot find -lqtmaind錯誤
這個錯誤是缺少某些庫，將mingw重新下載安裝即可。
6、編譯時可能會遇到如下錯誤：previous declaration 'long int InterlockedIncrement(long int*)' here
此爲qt的bug需要修改源代碼 （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、編譯錯誤，顯示 can not find -lqtmaind。
這是qt的debug庫，安裝完成後需要再自己編譯這個庫。在Qt的開始菜單中，你可以找到一個程序 Qt 4.4.0 (Build Debug Libraries)，運行這個程序就能編譯Qt的Debug庫了。