转:QT 的点点滴滴 错误总结

转自:http://blog.csdn.net/lbsljn/archive/2009/12/29/5099590.aspx

MinGw + CodeBlock + QT4.5

类定义后面要加";"

函数的实现部分,如果定义部分有void,则实现部分不能少;

检查include文件有无少;

error: request for member `show' in `((MainWindow*)this)->MainWindow::rightform', which is of non-class type `RightForm*'|
"->"与"."问题

函数"()"千万不能少;

connect中的SLOT里的自定义过程的申明一定要写在private slots:(或public slots:)下

QTableWidgetItem *newItemName = new QTableWidgetItem(tr("姓名"));
    newItemName->setFlags(newItemName->flags() & (~Qt::ItemIsEditable));//网格设置为只读
    tblWidgetMingPian->setItem(0, 0, newItemName);

newItemName = new QTableWidgetItem(tr("陈林
    
    
    
    
    
    & (~Qt::ItemIsEditable));
    tblWidgetMingPian->setItem(0, 1, newItemName);

tblWidgetMingPian->verticalHeader()->hide();
    tblWidgetMingPian->horizontalHeader()->hide();
    tblWidgetMingPian->setRowHeight(0,25);
    tblWidgetMingPian->setRowHeight(1,25);
    
    
        tblWidgetMingPian->setRowCount(2);connsql.h
    tblWidgetMingPian->setColumnWidth(0,60);
    tblWidgetMingPian->setColumnWidth(1,100);
    
    
    if 里面的语句要加括号 if (条件)
    
    枚举类型的定义:
    typedef enum{
        nil,
        ready,
        fired,
        exceptional
    }Status;
    
   
    QString text = tr("%1 %2").arg(i + 1).arg(files[i]);
    
    
Error:ISO C++ forbids declaration of `NavItem' with no type     
如果出现以上的错误,其中NavItem是自定义类,则需检查有没Include进此类的定义头文件,
并检查头文件的#ifndef中的名称跟其他类有没重复(在复制其它类生成新类时经常会出现这样的错误)

=====================================================================================
\mingw\lib\libmingw32.a(main.o):main.c:(.text+0x104)||undefined reference to `WinMain@16' |
往pro文件按顺序加入下面三行:
     -lmingw32 \
     -lSDLmain \
     -lSDL \
     
     sdl库中文件(sdl.h)里将 #include "SDLMain.h" 注释掉,否则qDebug(),printf全部无法显示 
     
     有可能使用 #pragma message()造成,方法:不使用#pragma message()

========================================================================
cannot open output file debug\umpcphonegui.exe: Permission denied
 产生此问题是由于文件umpcphonegui.exe受到保护,写不进去,打开任务管理器结束掉此进程就好了
========================================================

pages.h|16|error: expected class-name before '{' token|
||=== Build finished: 1 errors, 0 warnings ===|
处理方法:没有include进所需的类

链接时提示""undefind reference to 'vtable for xxx'错误的处理方法: 重新makefile试下或
工程文件(.pro)中的HEADERS中没有加入定义该类的.h文件;另一原因,虚函数(或调用的虚函数)定义后没有加"=0";

int x,y;
    setupUi(this);
    this->move(10,60);
    this->resize(338,568);
    x = this->x() + this->frameGeometry().width();
    y = this->y() + 20 ;
    //showMaximized();
    rightform = new RightForm;
    rightform->move(x,y);

ERROR:undefined reference to `RightGpsForm::RightGpsForm(QWidget*)
工程文件(*.pro)文件中的Source没有加入RightGpsForm类实现的.cpp文件
头部定义有误,需检查头部名称跟文件名是否一样;
尝试重编译
    
error: ISO C++ forbids declaration of `GPSMainWindow' with no type|    
类的定义GPSMainWindow(gpsmainwindow.h)中的
#ifndef MAINWINDOW_H_INCLUDED
#define MAINWINDOW_H_INCLUDED
头部定义有误,需检查头部名称跟文件名是否一样;
    
    
#include 时,提示下面的错误:    
QList: No such file or directory   
解决方法:
Project-build options-选择整个工程(左侧第一项)--切到右边的页"Search directories"
增加"$(#qt4.include)\QtGui\QtCore"

QT中的目录用"/"表示

应用程序目录:QCoreApplication::applicationDirPath().append(tr("/world.png"));

=========================
QSS:
设置TabWidget中的Tab页高度
QTabBar::tab {
  height: 14ex;
  width: 14ex;
}

======================
TRACE_SUBSYSF(MYRUNLEVEL,MYMODULENAME,QString(QObject::tr("测试数据"))<<10);

TRACE_LEVEL=5 TRACE_SUBSYS=MAIN /d/study/umpcapp/umpcapp-dev-1.0.0/gpsapp/deb
ug/gpsapp.exe

TRACE_SUBSYSF(5,"GUIAPP",QString(QObject::tr("构造函数创建完毕"))<<10);

TRACE_SUBSYSF(5,"GUIAPP",tr("构造函数创建完毕")<<10);

int ret = QMessageBox::question (this, tr("提示"),
                                         tr("确定要删除文件吗?"),
                                         QMessageBox::Yes | QMessageBox::No,
                                         QMessageBox::No);
                                         
         
引用Dll文件(动态链接"qextserialport.dll")时,需在pro里加下面的语句, -l+dll文件名                                         
LIBS += -lqextserialport

//
//    listWidget->addItem("a");
//    listWidget->addItem("b");
//    QVariant var;
//    var.setValue (new int(789098));
//
//    listWidget->item(0)->setData(Qt::UserRole,var);
//
//    int* ptr = listWidget->item(0)->data(Qt::UserRole).value < int* >();
//    qDebug()<< "RecentNoteListForm::RecentNoteListForm:" << *ptr << endl;
//    delete ptr;
//    delete &listWidget->item(0)->data(Qt::UserRole);

删ITEM方法:
把把ITEM的数据挂到指针上,先删ITEM,然后再删除指针

如果发生 no such file or directory not find(报QT核心文件错)
有可能是project --properties--projects settings中的"This is a custom MakeFile"没有勾选;
检查.pro文件是   INCLUDEPATH += DEPENDPATH+= 有没加入文件所在的目录
检查.pro文件是否引入两个版本不同的相同文件名的文件;

============================================
枚举类型做为信号的参数,则需对枚举类型进行注册
在include中
//定义Enum
typedef enum{
    ProgressType,
    StartType,
    SuccessType,
    StopType
}SyncMsgType;
//定义结构
typedef struct  //实际使用中可以多增加些结构成员
{
    SyncMsgType msgtype;
}SyncMsg;

Q_DECLARE_METATYPE(SyncMsg)

在应用程序.CPP中
//连接之前再注册
    qRegisterMetaType("SyncMsg");
    connect(gpssyncthread, SIGNAL(syncMsgNotify(SyncMsg)),
            this, SLOT(syncMsgEvent(SyncMsg)));  
========================================
QList<itemdata*> listItemDatas;

for (QList<itemdata*>::iterator it=listItemDatas.begin(); it!=listItemDatas.end() ; ++it)
    {
        (*it)->colName;
    }
    
    
==================    
error: multiple types in one declaration

自定义的类 {}后面没有";"
还有一种可能是pro文件中引用了两次单元文件;
=====================================
expected unqualified-id before "int"
前一句的";"误写为","
======================================

在Bulid工程时,qmake *.pro死循环,原因:pro文件里同一文件包含两次;

===========================

char *const p ; p所指向的值不能变;
char cont *p; P所指向的地址不能变;

===========================
error: `nameLineEdt' was not declared in this scope
函数域没有写; (函数域::函数名())
ifdef/define重覆

==============================
int main(int argc, char *argv[])
{
    Q_INIT_RESOURCE(qtdam);
    
    QApplication app(argc, argv);
    QSplashScreen *splash = new QSplashScreen;
    QString path=app.applicationDirPath();
    IDIOMA *lang = new IDIOMA();
    lang->setfile_idioma(path+"/languages.lng");
    if (lang->idioma_seleccionado=="Español")
        splash->setPixmap(QPixmap(":/images/splash_espagnol.png"));
    else
        splash->setPixmap(QPixmap(":/images/splash.png"));
    splash->show();
    Qt::Alignment topRight = Qt::AlignRight | Qt::AlignTop;
    splash->showMessage(lang->leer_idioma("1"),topRight, Qt::white);
    MainWindow mainWin;
    mainWin.show();
    splash->finish(&mainWin);
    delete splash;
    return app.exec();
}

===============================
函数如果有返回值必须写,否则有造成一些不确定的错误
如: 
QString a()
{
}

QString str;
str = "abc";
str.append(a());
QMessageBox::warning(this, tr("呼叫"),str,QMessageBox::Ok);

上面的情况,对话框可以出来,但点击对话框中的"确定"后,程序会死在那;
=====================================================

进行信号连接时,要确保连接参数中的对象已经创建过,否则会报保护错;

图片加载不了,有可能是QT库中的插件库没有拷贝;
加载路径指令:

QCoreApplication::addLibraryPath(QObject::tr("%1%2plugins").arg(QCoreApplication::applicationDirPath()).arg("/"));
        qDebug() << "插件加载的路径是(QCoreApplication::libraryPaths):" << QCoreApplication::libraryPaths()<<endl; <br="">        
有三个插件加载路径 1,应用程序路径;2,QTDIR环境路径,3,加入的路径;      
=============================================================

TRACE_LEVEL=5 TRACE_SUBSYS=DB /d/study/umpcapp/umpcapp-dev-1.0.0/debug/gpsapp.exe

===============================================
 void DragWidget::mousePressEvent(QMouseEvent *event)
 {
     QLabel *child = static_cast<qlabel*>(childAt(event->pos()));
     if (!child)
         return;

QPixmap pixmap = *child->pixmap();

QByteArray itemData;
     QDataStream dataStream(&itemData, QIODevice::WriteOnly);
     dataStream << pixmap << QPoint(event->pos() - child->pos());
     
     
=================================================     
取得应用程序所在路径,注:结果后面未加"/"
QCoreApplication::applicationDirPath()
===================================================

*.hpp文件,如果改动,Bulid后对改动后代码不起作用,必须ReBulid才可以;
=================================================================
静态成员变更量
aa.h
class AA
{
  static char p[13];
};

aa.cpp

char AA::p[13];

如果没在cpp中增加"char AA::p[13];",则编译时会提示"undefined reference to...."的错误
====================================================================
b.h接口中引用a.h接口
使用时必须加上
include "a.h"
include "b.h"

否则编译时会出现"如果没在cpp中增加"char AA::p[13];",则编译时会提示"
=========================================================================

单例模式singleton单元要最先初始化(#include放到最前面)

===========================================================
QWidget类以模式窗体显示:
    dailPage = new DailForm(0,tel);
    dailPage->setWindowModality(Qt::ApplicationModal);
    dailPage->show();

================================================================
事件过滤写法:
其实可以通过重载QWidget::keyPressEvent()获得本类(假设是窗体)中的几乎所有键盘事件,但焦点在文本框上,就不属于窗体类啦,所以必须采用在窗体类中添加Event Filters:

CustomerInfoDialog::CustomerInfoDialog(QWidget *parent)
  : QDialog(parent)
{
  ...
  firstNameEdit->installEventFilter(this);
  lastNameEdit->installEventFilter(this);
  cityEdit->installEventFilter(this);
  phoneNumberEdit->installEventFilter(this);
}

然后在eventFilter中处理相关键盘事件,通过target判断是否是文本框发生的键盘事件

bool CustomerInfoDialog::eventFilter(QObject *target, QEvent *event)
{
  if (target == firstNameEdit || target == lastNameEdit
        || target == cityEdit || target == phoneNumberEdit) {
    if (event->type() == QEvent::KeyPress) {
        QKeyEvent *keyEvent = static_cast(event);
        if (keyEvent->key() == Qt::Key_Space) {
          focusNextChild();
          return true;
        }
    }
  }
  return QDialog::eventFilter(target, event);
}

========================================================================    
去掉窗体标题栏:
setWindowFlags(Qt::FramelessWindowHint);
==============================================================
ld.exe cannot find -lSDL 
处理:环境变量path加入"D:\QtDevelop\umpcapp\public\SDL-1.2.13\bin"
===========================
环境变量path的设置:
D:\QtDevelop\umpcapp\public\STLport-5.1.3\bin;
D:\MinGW\bin;
D:\Qt\bin;
D:\QtDevelop\umpcapp\public\SDL-1.2.13\bin;
D:\QtDevelop\umpcapp\public\SDL_mixer-1.2.8\bin

注:STLport-5.1.3一定要放在MinGW前面,不然会出现
"QImage: out of memory, returning null image"的错误;
==================================================
如果要用到STLport库,那么在配置.pro文件时,一定要记住把stlport放在其它库的前面,
下面的写法是正确的:
INCLUDEPATH += . \
               ../../public/STLport-5.1.3/stlport \ ###这句一定要放在前面
               ../../public/SDL-1.2.13/include \
               ../../public/common/include \
               ../../public/qextserialport-1.1\
               ../../public/boost-1.37.0/include
================================  
如果库的依赖关系(*.dll)出错,则应用程序会出现报内存的错误,最简单的方法就是把应用程序
所需要的库直接加入环境变量path中,以造成如果库更新,原来拷在应用程序下的库没有及时更新,环境
变更path的设置例子:
path += D:\QtDevelop\umpcapp\public\boost-1.37.0\lib;
        D:\QtDevelop\umpcapp\public\qextserialport-1.1\build 
上面对应的库为:
boost_system-mgw34-mt-1_37.dll;boost_thread-mgw34-mt-1_37.dll;
qextserialport.dll

==================================================
编译成功后,debug下的exe文件不能生成,请检查.pro文件中,HEADERS与SOURCES参数配置是否有错误,
比如把.h文件加入SOURCES参数中,把.cpp加入HEADERS参数中.

==========================================================

void MapScene::mouseMoveEvent ( QGraphicsSceneMouseEvent * mouseEvent )
{
    QPointF scenepos;
    scenepos = mouseEvent->scenePos();
    //qDebug()<<qstring::number(scenepos->x())<<qstring::number(scenepos->y())<<endl;
    emit mapPosNotify(scenepos.x(), scenepos.y());
    QGraphicsScene::mouseMoveEvent(mouseEvent);
}

===========================================================
QWebKit中支持Flash播放的代码(Qt4.5才支持Flash)
webView->page()->settings()->setAttribute(QWebSettings::PluginsEnabled,true);

=================================
listWidget->addItem(new QListWidgetItem(QIcon(":/notepaditem.png"), QFile(files[i]).fileName()  ));
==========================================================
vector 引用的单元:
#include 
using namespace std;
==============================
QString 字符串换行:
QString str;
str = tr("133");
str.append(tr("
"));

注:br后要加一个空格;
=======================================================
Qss背景透明:
QPushButton{
   
}

==========================================
打开指定URL地址

QUrl url("http://www.zzwtt.com ");
QDesktopServices::openUrl(url);
可以打开任意URL

===================================
窗体置前:
QWidget w;
   w.setWindowFlags(Qt::WindowStaysOnTopHint);
   w.show();

==================================================
窗体不显示在任务栏:
setWindowFlags(Qt::Popup) ;
==============================
注:改变*.h的内容,编译时会没有编译过程,只有改变*.cpp才会进行编译;

================================================
编译win32 中的 dll工程配置方法(以skypebackend为例):
  因为工程中的代码全是标准C++的代码,所以编译方式跟QT有点不一样,
  Project-properties...-Project settings页中的"This is a custom Makefile"前面的方框不要勾选;
  Project-properties...-Build targets 右边中的"Type"设置为"Console application"(skypebackend为控制台程序)
  Project-build options-Linker settings页,设置Link libraries内容为:(win32库文件)
     ..\..\..\..\MinGW\lib\librpcdce4.a
     ..\..\..\..\MinGW\lib\librpcns4.a
     ..\..\..\..\MinGW\lib\librpcrt4.a
     
==============
按回车定位到下一焦点:
connect(lineEdit1, SIGNAL(returnPressed()), lineEdit2, SLOT(setFocus()));
======================================= 
项目翻译DEMO:
#include 
#include 
#include

int main( int argc, char **argv )
{
    QApplication app( argc, argv );

QTranslator translator( 0 );//Creates a QTranslator object without a parent
    translator.load( "ttl_zh-cn", "." );//Try to load a file called ttl_zh-cn.qm
    app.installTranslator( &translator );//Add the translations from ttl_zh-cn.qm to the pool of translations

QPushButton hello( QPushButton::tr( "Hello world!" ), 0 );

app.setMainWidget( &hello );
    hello.show();
    return app.exec();
}

1.使用qmake -project生成.pro文件;
2.在.pro文件中加上如下语句:
TRANSLATIONS    = ttl_zh-cn.ts
3.运行如下命令:
lupdate ttl.pro
生成ttl_zh-cn.ts文件;(PS:.ts的名字来自“翻译源”(translation source))
4.运行如下命令:
linguist ttl_zh-cn.ts
这时候会弹出一个图形界面工具:
    1)单击左边窗口的QPushButton
    2)双击中间窗口的helloworld!这时会弹出一个对话框,在Translation下输入:你好世界!
    3)单击工具栏的Done and Next按钮(这个时候QPushButton的前面会变成绿色的对号)显示翻译完成
    4)然后File->Release,这个是生成.qm文件(.qm来自“QT消息”Qt message),保存到当前目录下
也可以使用命令release ttl_zh-cn.ts来生成.qm文件的。
    5)点击linguist“X”退出窗口,这个时候会提示保存ttl_zh-cn.ts文件,单击save,完成操作。
这一步的目的是把“你好世界!”来替代ttl_zh-cn.ts中的“unfinished”,这个只要了解就可以了,有兴趣的可以去看看QT参考文档。
5.运行如下命令:
qmake ttl.pro
6.运行如下命令:
make
7.运行如下命令:
./ttl
这个时候你会发现按钮是显示的是:“你好世界!”  而不是“helloworld!”

PS:lupdate和lrelease命令都可以带参数-verbose,这样会显示一些提示信息。这个 参数是可选的。

通过上面的步骤可以完成正常的翻译,但对象QLineEdit的右键菜单显示的还是英文,解决方法:
把Qt\translations目录下的qt_zh_CN.ts里面的内容全部拷到自己项目ts文件的后面就可以了(也就是把两个ts文件合并)
============================================================
====================================================

4字节空间存INT类型:
    #define USERGROUP_WIDTH 5;
    char buff[5];
    int groupid = atoi(groupId.trimmed().toAscii().data()); //得到GroupID的int值
    char* gid = (char*)(&groupid);      //将groupid转化为char*类型
    memcpy(buff, gid, USERGROUP_WIDTH-1);
    
    char p[4];
    memset(buff, 0, USERGROUP_WIDTH);
    memcpy(buff, p, USERGROUP_WIDTH-1);
    int  gid = *((int*)(&buff)); 
==================================  
错误信息:redefinition class...
请核对
#ifndef IGPSINTERACTION_H_INCLUDED
#define IGPSINTERACTION_H_INCLUDED
上面两行中的名称是否一样(出现过第两行中最后一个"D"没掉, 找了N久才查出问题,汗~~~)
另一原因是变量定义不可放在.h文件中,如下
struct mystruct{
  ...  
};
是一个变量 (不可放在.h文件中实现)
typedef struct MyStruct{
 ....
}mystruct;
其中 MyStruct是一种类型,而mystruct是一个变量
标准用法
在.h文件中
typedef struct MyStruct{
 ....
};
在.cpp中定义变量
struct MyStruct mystruct;
=========================================================
std::string 转QString:
std::string  groupName = 'abcdef';
const char *groupNameCh = groupName.c_str();
QString tmpStr = QObject::tr(groupNameCh);

=================================================
窗体在执行destory()时,qapp对象就已经退出啦;
===============================================
gsoap项目中的错误:multiple definition of `namespaces'
解决方法:用gsoap中的工具生成的 nsmap文件(#include "UMPCServer.nsmap")引用不能写在.h中,应该要写在.cpp文件中;
a.cpp:
#include "UMPCServer.nsmap"
上面的写法是正确的,不能写在a.h文件中,否则就会报错

================
删除TreeWidget结点:
void MainWindow::clearTreeWidget()
{
    while ( treeWidget->topLevelItemCount() > 0 )
    {
        QTreeWidgetItem *parentItem = treeWidget->takeTopLevelItem(0);
        QList list = parentItem->takeChildren ();

for (int j = 0; j < list.size(); j++)
        {
            QTreeWidgetItem *childItem = list.at(j);
            delete &nodeItemData(childItem);
            delete childItem;
        }
        delete &nodeItemData(parentItem);
        delete parentItem;

}

}
=======================================================
IGPSNestData* resolveRecord(const QSqlRecord &record,const DataType &dateType )
error: expected `,' or `...' before '&' token

解决方法 #include

===========================================================
GpsSideBar::IGPSNestData* GpsSideBar::resolveRecord(const QSqlRecord &record,const GpsSideBar::DataType &dateType );
{

}
error: declaration of `GpsSideBar::IGPSNestData* GpsSideBar::resolveRecord(const QSqlRecord&, const GpsSideBar::DataType&)' outside of class is not definition
解决方法:去掉函数头最后的";"
GpsSideBar::IGPSNestData* GpsSideBar::resolveRecord(const QSqlRecord &record,const GpsSideBar::DataType &dateType )
{

}

============================================================
QTreeWidget/QTreeView中的CheckStatus状态的级联更新
void GpsSideBar::on_treeWidget_itemChanged ( QTreeWidgetItem * item, int column )
{
    if (!item || column != 0)
        return;

Qt::CheckState state = item->checkState(0);
    QTreeWidgetItem *parent = item->parent();

if (parent)
    {
        int number = 0;
        int partiallyCheckedNum = 0;
        for (int row = 0; row < parent->childCount(); ++row)
        {
            if (parent->child(row)->checkState(0) == Qt::Checked)
                ++number;
            if (parent->child(row)->checkState(0) == Qt::PartiallyChecked)
                ++partiallyCheckedNum;
        }
        if (number == 0)
        {
            if (parent->checkState(0) != Qt::Unchecked && partiallyCheckedNum == 0)
                parent->setCheckState(0, Qt::Unchecked);
            else if (parent->checkState(0) != Qt::PartiallyChecked && partiallyCheckedNum > 0)
                parent->setCheckState(0, Qt::PartiallyChecked);

}
        else if (number == parent->childCount())
        {
            if (parent->checkState(0) != Qt::Checked )
                parent->setCheckState(0, Qt::Checked);
        }
        else
        {
            if (parent->checkState(0) != Qt::PartiallyChecked )
                parent->setCheckState(0, Qt::PartiallyChecked);
        }
    }

if (item->childCount() > 0)
    {
        int row;
        if (state == Qt::Checked)
        {
            for (row = 0; row < item->childCount(); ++row)
            {
                if (item->child(row)->checkState(0) != Qt::Checked)
                    item->child(row)->setCheckState(0, Qt::Checked);
            }
        }
        else if (state == Qt::Unchecked )
        {
            for (row = 0; row < item->childCount(); ++row)
            {
                if (item->child(row)->checkState(0) != Qt::Unchecked)
                    item->child(row)->setCheckState(0, Qt::Unchecked);
            }
        }
    }
}

==========================================
清空QTreeWidget/QTreeView所有结点(gpssidebar.cpp文件中提取):
void GpsSideBar::clearTreeWidget(QTreeWidget *treeWidget)
{
    while ( treeWidget->topLevelItemCount() > 0 )
    {
        QTreeWidgetItem *parentItem = treeWidget->takeTopLevelItem(0);
        QList list = parentItem->takeChildren ();

for (int j = 0; j < list.size(); j++)
        {
            QTreeWidgetItem *childItem = list.at(j);
            delete &GetGPSNestData(childItem);
            delete childItem;
        }
        delete &GetGPSNestData(parentItem);
        delete parentItem;

}
}

==========================================================
ini配置文件中的字段名是区分大小写的

=========================================================
 void MainWindow::contextMenuEvent(QContextMenuEvent *event)
 {
     QMenu menu(this);
     menu.addAction(cutAct);
     menu.addAction(copyAct);
     menu.addAction(pasteAct);
     menu.exec(event->globalPos());
 }
 
 ==================================================
让QLineEdit不弹出右键菜单:
QLineEdit->setContextMenuPolicy(Qt::NoContextMenu);

=========================================
计算坐标两点间的角度:
第一种方法:
double calcAngle(const QPointF& centerPos,const QPoint& pos)
{
    double px1,px2,py1,py2;
    px1 = centerPos.x();
    py1 = centerPos.y();
    px2 = pos.x();
    py2 = pos.y();
    double x = px2 - px1;
    double y = py2 - py1;
    double hyp = sqrt(pow(x,2) + pow(y,2));
    double cos = x / hyp;
    double rad = acos(cos);
    double deg = 180/(M_PI / rad);
    if (y < 0)
    {
        deg = -deg;
    }
    else if ((y == 0) && (x <0))
    {
        deg = 180;
    }
    deg = deg + 90;
    if (deg < 0)
    {
        deg = deg + 360;
    }
    return deg;
}
第二种方法:
int calcAngle(const double& sx,const double& sy,const double& dx,const double& dy)
{
    double x, y, k1, k2;
    x = dx - sx;
    y = dy - sy;
    if ( (x == 0) && (y == 0) )
    {
        return 0;
    }
  if (x == 0)
  {
      if ( y < 0) return 0;////在X轴上时两种结果
      if ( y > 0) return 180;
  }

if ( y == 0)
  {
      if ( x > 0 ) return 90;//在Y轴上时两种结果
      if ( x < 0) return 270;
  }

k1 = 0; //因为直线(L1)在Y轴上,所以方程为:y=0x+0;即Y=0;斜率为0
  k2 = y / x; //直线(L2)的斜率为 y/x,前面已经去除了x=0或y=0的情况
  int  result = round(atan(fabs(k1 - k2)) * 180 / M_PI);
  //由于K1=0,所以 a := abs(k1 - k2) / abs(1 + k1 * k2);
  if ( (x > 0) && (y < 0) )
  {
      result = 90 - result;
  }
  else if ( (x > 0) && (y > 0) )
  {
      result = 90 + result;
  }
  else if ( (x < 0) && (y > 0) )
  {
      result = 270 - result;
  }
  else if ( (x < 0) && (y < 0) )
  {
      result = 270 + result;
  }
  return result;

}
==============================================================
void MainWindow::setCurrentFile(const QString &fileName)
{
    curFile = fileName;
    if (curFile.isEmpty())
        setWindowTitle(tr("Recent Files"));
    else
        setWindowTitle(tr("%1 - %2").arg(strippedName(curFile))
                                    .arg(tr("Recent Files")));

QSettings settings("Trolltech", "Recent Files Example");
    QStringList files = settings.value("recentFileList").toStringList();
    files.removeAll(fileName);
    files.prepend(fileName);
    while (files.size() > MaxRecentFiles)
        files.removeLast();

settings.setValue("recentFileList", files);
    
=======================================

setMouseTracking(true)是打开鼠标移动跟踪,默认情况下只有在鼠标按下后才会发送
QMouseMoveEvent()事件,打开鼠标移动跟踪后就能够随时发送了.

================================================
QT获取mysql包含中文的值  
QString lname2 = QString::fromUtf8(query.value(0).toByteArray());
qDebug()<<qobject::tr("lname fromutf8="=">")<<lname2<<endl; <="" p="">

===========================================================
QTreeWidgetItem::setData ( int column, int role, const QVariant & value )用法:

自定义一个类:
class ItemData
{
public:
  QString name;
  int age;
};
Q_DECLARE_METATYPE(ItemData);
//把数据指针存入结点Data:
void GpsSideBar::setItemData(QTreeWidgetItem * item,ItemData *itemData)
{
    //item->setData(0,Qt::UserRole, qVariantFromValue(ItemData(*itemData)) );
    item->setData(0,Qt::UserRole, qVariantFromValue( int(itemData) ) );
}
//取值
ItemData* GpsSideBar::GetGPSNestData(QTreeWidgetItem *item)
{
    //return qVariantValue(item->data(0,Qt::UserRole));
   return  reinterpret_cast <itemdata*>( qVariantValue(item->data(0,Qt::UserRole)) );
}

===========================================================
在linux下运行designer不能正常显示中文的解决方法:
在qtconfig中设置font为Bitstream Charter,然后保存就OK了
=======================================
移交控制权
qApp.processEvents();
相当于delphi中的application.processmessage;
==================================================
Qt Script Debugger — 用于调试Qt Script的工具,可以单步运行,查看输出等。 
Qt文档里有很详细的一篇专门讲这个的,有兴趣的来看下: Qt Script Debugger Manual
=============================================
Com口大于10需经特殊处理: \\\\.\\COMxx    如  \\\\.\\COM10 等价于 COM10;
====================================================

透明的控件的TranslucentBackground属性为true (继承了parent的属性), 
而非透明的控件则在代码中强制将TranslucentBackground设为了false,
 这样就造就了有意思的结果。 代码片段如下:
label = new QLabel(”www.cuteqt.com”);
label->setAttribute(Qt::WA_TranslucentBackground, false); //设置为false完全不透明
label->setAutoFillBackground(true);

=======================
怎样将日志输出到文件中
void myMessageOutput( QtMsgType type, const char *msg )
{
    switch ( type ) {
        case QtDebugMsg:
            //写入文件;
            break;
        case QtWarningMsg:
            break;
        case QtFatalMsg:
            abort();
    }
}

int main( int argc, char** argv )
{
    QApplication app( argc, argv );
    qInstallMsgHandler( myMessageOutput );
    ......
    return app.exec();
}

qDebug(), qWarning(), qFatal()分别对应以上三种type。

=======================================================
QGraphicsView的updateSceneRect
有 些时候,当你往一个QGraphicsView中添加一个空的QGraphicsScene并且批量地在这个QGraphicsScene中添加上大量的 自定义的图形对象时,会发现QGraphicsView显示出来的图像有些偏移:有足够的空间来显示这些图形,可是有些图形画到 QGraphicsView的边缘去了以致于没有完全显示出来。
这是因为当前的消息循环还没有处理完毕,因此QGraphicsView的槽“updateSceneRect”还没有被调用。这样它的sceneRect没有刷新,就没有将更改过大小的scene移动到中心点了。
解决办法是在添加完毕图形对象之后立即调用updateSceneRect,使之刷新sceneRect。

=======================================================
QGraphicsView绘图问题
    QGraphicsScene scene;
    scene.setSceneRect(0, 0, 800, 800);
    QGraphicsLineItem *line = new QGraphicsLineItem(0, 0, 500, 500);
    scene.addItem(line);
    QGraphicsView *view = new QGraphicsView(&scene);
上面这段代码,如果把view作为主窗体在main函数中显示出来,线会正常的画出来.
但一但有其它窗体作为主窗体,比如MainWindow,然后在其构造函数或其它函数中调用这这段代码,
view可以显示出来,但线不会被画出来.(无论是作为单独的窗体还是作为MainWindow的
CentralWidget都不会被画出来,看了sample里面的几乎完全一样的代码却正常

解决方法:
  scene是局部变量,函数结束后被销毁了,应该用
  QGraphicsScene *scene = new QGraphicsScene(this);
  但问题是为什么main函数中这样用不会出问题?
    因为你那个main函数没有结束,这个函数是要到程序结束时结束的,所以那个临时变量没有删除,
    这样用就没有问题。其他的函数调用完就结束了。
================================
    
=======================
查出通讯录中代理不能取得焦点的BUG原因:MainWindow 要是继续自QMainWindow或QWidget就
取不了焦点,但如果继承自QDialog则可以取得焦点
===================================================
窗体CallingCardEdtFrm(继承自QWidget),在此窗体上创建个组件
QListWidget,QListWidget中的QListWidgetItem(里面有个QLineEdit编辑组件)的绘制与
显示使用代理实现
class CallingCardEdtDlg:public QDialog //如此继承自QMainWindow或QWidget则QLineEdit获取不了
                          //焦点并且不能输入,但如果继承自QDialog就没问题了
{
 Q_OBJECT
 public:
   CallingCardEdtDlg(QWidget*);

};
CallingCardEdtDlg::CallingCardEdtDlg(QWidget* parent)
        :QDialog(parent)
{
    CallingCardEdtForm * frm = new CallingCardEdtForm(0);
    frm->setGeometry(0,0,200,200);

QStackedWidget* stackedWidget = new QStackedWidget(0);
    stackedWidget->addWidget(frm);
    stackedWidget->setCurrentIndex(0);
    QGraphicsScene* scene = new  QGraphicsScene();
    QGraphicsView* view = new QGraphicsView(scene);
    view->setParent(this);
    QGraphicsProxyWidget* proxyWidget = new QGraphicsProxyWidget();
    proxyWidget->setCacheMode(QGraphicsItem::DeviceCoordinateCache);
    proxyWidget->setWidget(stackedWidget);
    scene->addItem(proxyWidget);

//view->resize(200,200);
    view->setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
    //view->setBackgroundBrush(QPixmap(":/No-Ones-Laughing-3.jpg"));
    view->setCacheMode(QGraphicsView::CacheBackground);
    view->setViewportUpdateMode(QGraphicsView::BoundingRectViewportUpdate);
    view->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    view->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    view->setBackgroundBrush(QColor("#151C28"));//
}    
    
======================================================================

事件原型申明中的类型定义不能加默认值
============================================

QPainterPath 画出的图形会闪烁的问题:
用下面的写法画出的图形会闪烁

class MyClass: public QWidget
{
public:
  MyClass(QWidget*);
private:
    QPainterPath* route;
    void paintEvent(QPaintEvent*e);
};
MyClass::MyClass()
{
  route = new QPainterPath();
}
void MyClass::paintEvent( QPaintEvent*e)
{
    QPainter *painter = new QPainter(this);
    //画校正图形
    int insideR = 30;
    int outsideR = 50;
    QColor insideColor(237,29,12); //内圆线条颜色
    QColor outSideColor(237,29,12); //外圆线条颜色
    QColor lineColor(237,29,12); //直线颜色
    QColor insideBrushColor(255,0,0,25);//内圆画刷颜色,最后的参数代表透明度( 0(完全透明)-100(不透明) )
    QColor outsideBrushColor(255,0,0,50);//外圆画刷颜色,最后的参数代表透明度( 0(完全透明)-100(不透明) )

//QPainterPath path;

route->moveTo(insideR,0);
    route->lineTo(outsideR,0);
    route->arcTo(0-outsideR,0-outsideR,outsideR*2,outsideR*2,0,180);
    route->lineTo(0-insideR,0);
    route->arcTo(0-insideR,0-insideR,insideR*2,insideR*2,0,180);

route->moveTo(0-insideR,0);
    route->lineTo(0-outsideR,0);
    route->arcTo(0-outsideR,0-outsideR,outsideR*2,outsideR*2,180,180);
    route->lineTo(insideR,0);
    route->arcTo(0-insideR,0-insideR,insideR*2,insideR*2,180,180);
    painter->setPen(Qt::NoPen);
    painter->setBrush(outsideBrushColor);
    painter->drawPath(*route);

painter->setBrush(Qt::NoBrush);
    painter->setPen(outSideColor);
    painter->drawEllipse( QPointF(0,0),outsideR,outsideR );

painter->setBrush(insideBrushColor);
    painter->setPen(insideColor);
    painter->drawEllipse( QPointF(0,0),insideR,insideR );

painter->setPen(lineColor);
    QPoint p1(0,  0- outsideR - 10  );
    QPoint p2(0,  outsideR + 10  );
    painter->drawLine(p1,p2);
    painter->rotate(90);
    painter->drawLine(p1,p2);
    painter->rotate(-90);
    delete painter;

}

如下用下面的写法则不会闪烁:
void MyClass::paintEvent( QPaintEvent*e)
{
    QPainter *painter = new QPainter(this);
    //画校正图形
    int insideR = 30;
    int outsideR = 50;
    QColor insideColor(237,29,12); //内圆线条颜色
    QColor outSideColor(237,29,12); //外圆线条颜色
    QColor lineColor(237,29,12); //直线颜色
    QColor insideBrushColor(255,0,0,25);//内圆画刷颜色,最后的参数代表透明度( 0(完全透明)-100(不透明) )
    QColor outsideBrushColor(255,0,0,50);//外圆画刷颜色,最后的参数代表透明度( 0(完全透明)-100(不透明) )

QPainterPath path;

path.moveTo(insideR,0);
    path.lineTo(outsideR,0);
    path.arcTo(0-outsideR,0-outsideR,outsideR*2,outsideR*2,0,180);
    path.lineTo(0-insideR,0);
    path.arcTo(0-insideR,0-insideR,insideR*2,insideR*2,0,180);

path.moveTo(0-insideR,0);
    path.lineTo(0-outsideR,0);
    path.arcTo(0-outsideR,0-outsideR,outsideR*2,outsideR*2,180,180);
    path.lineTo(insideR,0);
    path.arcTo(0-insideR,0-insideR,insideR*2,insideR*2,180,180);
    painter->setPen(Qt::NoPen);
    painter->setBrush(outsideBrushColor);
    painter->drawPath(path);

painter->setBrush(Qt::NoBrush);
    painter->setPen(outSideColor);
    painter->drawEllipse( QPointF(0,0),outsideR,outsideR );

painter->setBrush(insideBrushColor);
    painter->setPen(insideColor);
    painter->drawEllipse( QPointF(0,0),insideR,insideR );

painter->setPen(lineColor);
    QPoint p1(0,  0- outsideR - 10  );
    QPoint p2(0,  outsideR + 10  );
    painter->drawLine(p1,p2);
    painter->rotate(90);
    painter->drawLine(p1,p2);
    painter->rotate(-90);
    delete painter;

}
================================================
如何让QT程序只运行一次:
以下代码在Ubuntu,win下测试通过:

#include 
#include 
#include 
#include 
#include

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QSystemSemaphore sema("JAMKey",1,QSystemSemaphore::Open);
    sema.acquire();//在临界区操作共享内存  SharedMemory
    QSharedMemory mem("SystemObject");//全局对象名
    if (!mem.create(1))//如果全局对象以存在则退出
    {    
        qDebug()<<mem.errorstring();
        sema.release();//如果是Unix系统,会自动释放。
        return 0;
    }
    sema.release();//临界区

QLabel label("Demo");
    label.show();
    return app.exec();//释放栈上的mem对象。
}

=========================================
打印当前代码行所在的文件与行:
qDebug()<<"所在文件:"<<qstring(__file__);
qDebug()<<"所在行:"<<qstring(__line__);< p="">

=======================================
undefined reference to `qInitResources_gui()'

pro文件中,请注意 "RESOURCES += "不可写成"RESOURCES = ";

============================================================

*.pro :    unix: DEFINES += __LINUX__

#ifdef __LINUX__
  ...
#else
  ...
#endif
==========================================
取得信号对象指针:
QObject * QObject::sender() const

QToolButton* toolBtn = static_cast<qtoolbutton*>(sender());
===========================================
函数申明后面带有const 的函数,函数体里所调用的函数的申明后面肯定也要带有 const 
否则,编译不过
===================================

请教如何在Qt的pro文件中定义字符串宏
在qtcentre中一位高人的方法得到实现:
DEFINES += SHARE_DIR=\\\"字符串\\\ "
==============================================================

如果使用OObject::tr("你好")对汉字进行赋值,但使用 qDebug()打印时出现乱码,有可能是*.cpp文件编码
有误,请把*.cpp文件编码改为UTF-8编码;

===================================
error: new types may not be defined in a return type
error: return type specification for constructor invalid
请检查类定义后有没加";"
================================================
win下电脑待机方法:

static HANDLE hToken;
  static TOKEN_PRIVILEGES tp;
  static LUID luid;
  if(::OpenProcessToken(GetCurrentProcess(),
         TOKEN_ADJUST_PRIVILEGES|TOKEN_QUERY,
         &hToken))
  {
   ::LookupPrivilegeValue(NULL,SE_SHUTDOWN_NAME,&luid);
   tp.PrivilegeCount=1;
   tp.Privileges[0].Luid =luid;
   tp.Privileges[0].Attributes =SE_PRIVILEGE_ENABLED;
   ::AdjustTokenPrivileges(hToken,false,&tp,sizeof(TOKEN_PRIVILEGES),NULL,NULL);
  }
  ::SetSystemPowerState(true,true);
  
  ==============================
  改变QMessageBox的大小:
  创建一个QMessageBox:

QMessageBox msgBox(this);
msgBox.setWindowTitle(tr("MailBox Location"));

msgBox.setInformativeText(tr("You must ..... and so on and so forth"));

像这样改变它的大小:

1). msgbox.setGeometry ( int x, int y, int w, int h )

2). msgbox.resize(int w, int h)

结果什么都没有发生。

原因:QMessageBox::showEvent() 强制将其大小改变成了QT认为比较合适的大小。要改变它的大小可使用下面这种方法

class MyMessageBox : public QMessageBox {
protected:
void showEvent(QShowEvent* event) {
QMessageBox::showEvent(event);
setFixedSize(640, 480);
}
};

本文来自CSDN博客,转载请标明出处:http://blog.csdn.net/diaopan1985/archive/2009/08/01/4399128.aspx

=====================================================================
QString怎么转换成char

QString str ="123456";
str.toAscii().data(); //this return a char* or const char*
str.toAscii() return a QByteArray

QString Str; //Str = "asdfasdfasdf";
Str->toString().c_str();

====================================================
调用 Q_DECLARE_METATYPE  报以下错
..\..\..\..\Qt\src\corelib\kernel\qmetatype.h||In function 'void* qMetaTypeConstructHelper(const T*) [with T = ContactsInfoTabItemData]':|
..\..\..\..\Qt\src\corelib\kernel\qmetatype.h|152|instantiated from 'int qRegisterMetaType(const char*, T*) [with T = ContactsInfoTabItemData]'|
src\contactsinfotabitemdata.h|62|instantiated from here|
..\..\..\..\Qt\src\corelib\kernel\qmetatype.h|126|error: no matching function for call to 'ContactsInfoTabItemData::ContactsInfoTabItemData()'|

如果报以上相类似的错误,请对构造函数中的每个参数赋初值,下面的写法是错误的
class ContactsInfoTabItemData
{
public:
  ContactsInfoTabItemData(QString name,QString caption);
};
Q_DECLARE_METATYPE(ContactsInfoTabItemData);

正确的写法应为:
class ContactsInfoTabItemData
{
public:
  ContactsInfoTabItemData(QString name=QString(),QString caption=QString());
};
Q_DECLARE_METATYPE(ContactsInfoTabItemData);

===========================================================
如果程序莫名奇妙的退出,也不报DLL找不到的错误,请仔细检查Main函数体有没直接Return的语句,
以造成不提示,直接退出的错误;
=========================================================================================
在Qt中计算文本的宽度与高度
  http://www.cuteqt.com/blog/?p=1029 
=======================================
  
error: incomplete type %u2018nsIDOMComment%u2019 used in nested name specifier
产生此错误的原因:
  g++ gives this message if you've forward-declared a type, like this

class MyClass;

and then you try and access one of its members, like maybe:

MyClass::doSomething()

g++ is complaining that it hasn't seen the body of class MyClass yet, so it has no way to know what MyClass::doSomething is.

(In C++ jargon, an "incomplete type" is a type that's been forward-declared but not yet defined.)

===============================================================================
互斥用法:
QMutex mutex;

void GlobalVar::setUserInfo(const GlobalVar::UserInfo &userInfo)
{
    QMutexLocker locker(&mutex);
    this->userinfo = userInfo;
}
==================================================
自定义事件方法:
a.h:

#include "event.h"

typedef void ( EventDelegater::*SetWidgetParent )(QWidget*,QString  );

class test
{
public:
  Event OnSetWidgetParent;

private:
  inline void invokeSetWidgetParent(QWidget *parentWidget,QString widgetName);  
};

a.cpp:

inline void test::invokeSetWidgetParent(QWidget *parentWidget,QString widgetName)
{

if ( !OnSetWidgetParent.m_EventList.empty() )
    {
        // 循环事件列表
        Event< SetWidgetParent >::EventIterator iter;
        for ( iter = OnSetWidgetParent.m_EventList.begin();
                iter != OnSetWidgetParent.m_EventList.end();
                ++iter )
        {
            // 调用事件
            InvokeEvent( parentWidget, widgetName );

}
    }
}

触发事件:
  invokeSetWidgetParent(NULL,QString());

绑定事件方法:
  test->OnSetWidgetParent.Bind(this, &MainWindow::setWidgetParent);  
  
================================================
自定义宏的用法:
*.pro

DEBUGSAVETOFILE = 1
isEmpty(DEBUGSAVETOFILE){
    win32:debug {
        CONFIG += console
    }
}
else{
    DEFINES += __DEBUGSAVETOFILE__
}  
  
main.cpp:
#ifdef __DEBUGSAVETOFILE__
#pragma message( "__DEBUGSAVETOFILE__ is defined.")
    qInstallMsgHandler( messageOutput );
#else
#pragma message("win32:debug is defined.")

#endif
===================================================
qss 收集:
Setting QObject properties

From 4.3 and above, any designable Q_PROPERTY can be set using the qproperty- syntax.

For example,

MyLabel { qproperty-pixmap: url(pixmap.png); }
 MyGroupBox { qproperty-titleColor: rgb(100, 200, 100); }
 QPushButton { qproperty-iconSize: 20px 20px; }
If the property references an enum declared with Q_ENUMS, you should reference its constants by name, i.e., not their numeric value.
 ============================================

类成员函数里定义的临时指针不能做为参数传递;
函数里取得的指针无法返回到外面;

groupmanage.h:
class GroupManage
{
private:
    /// 组在线数据
    /** . */
    class OnLineData
    {
    public:
        IGPSNav* iGpsNav; /**< GPS聊天接口 */
        int groupId;  /**< 组ID */
    };
    QList<onlinedata*> onLineList; /**< 组在线列表 */
    
private:
    ///查找GPS聊天接口
    /**
      @param groupId 组id
      @param gpsNav(返回值) 只有在查到时才返回指针
      @return true:查找到 false: 未查找到
    */
    bool findGpsNav(int groupId,unsigned int & gpsNav);  //正确的写法:返回对象指针地址  
    
    bool findGpsNav(int groupId,IGPSNav* iGpsNav);//如果是这样写法请注意调用方法
    
    
    void test();
};

groupmanage.cpp:

//查找GPS聊天接口
bool GroupManage::findGpsNav(int groupId,unsigned int & gpsNav)
{

bool ok = false;
    for (int i=0; i < onLineList.count() ; i++)
    {
        OnLineData* onLineData = onLineList.at(i);
        if ( onLineData->groupId == groupId )
        {
            ok = true;
            gpsNav = (unsigned int)(onLineData->iGpsNav);

break;
        }
    }
    _EDEBUG("findGpsNav gpsNav="<<gpsnav);
    return ok;

bool GroupManage::findGpsNav(int groupId,IGPSNav* iGpsNav)
{

bool ok = false;
    for (int i=0; i < onLineList.count() ; i++)
    {
        OnLineData* onLineData = onLineList.at(i);
        if ( onLineData->groupId == groupId )
        {
            ok = true;
            iGpsNav = onLineData->iGpsNav;

break;
        }
    }
    _EDEBUG("findGpsNav gpsNav="<<igpsnav);
    return ok;
}
void GroupManage::test()
{
    IGPSNav* iGpsNav;
    unsigned int iGpsNavInt;
    bool ok;
    ok = findGpsNav(groupId,iGpsNavInt);
    iGpsNav = (IGPSNav*)iGpsNavInt;
    _EDEBUG("iGpsNav:"<<igpsnavint<<igpsnav);   正常返回<br="">    
    /*--下面的写法指针返回不了
    IGPSNav* iGpsNav; //把此句申明放在类的private:下就可以解决问题
    bool ok;
    ok = findGpsNav(groupId,iGpsNav); 
     _EDEBUG("iGpsNav:"<<igpsnavint<<igpsnav);   返回的指针为空<br="">    */
}

=============================================================

QPushButton{
   
}

透明度50%

===================================
1.问题1: connect函数不存在
对象没有从QObject继承.

2.问題2
采用Event方法连接,在对象方法里启动定时器,在运行时发生:
QT timers cannot be started from another thread
解决:
采用Signal/Slot并且连接方式采用 Qt::QueuedConnection

3.利用Signal/Slot删除对象本身:
解决:
采用Signal/Slot并且连接方式采用 Qt::QueuedConnection,这时在另一个对象中就可以删除对象本身了 
===========================================================

用qss增加每个菜单项的高度
在用StyleSheet美化QMenu时,如何指定菜单项与快捷键的间距?

QMenu::item {

border: 1px solid transparent; 
  
  margin: 0px 2px 0px 2px; 
  
  padding: 2px 9px 2px 30px; // Top Right Bottom Left(用这种方式能增加menu中每一行的高度,这就使得在小的触摸屏上进行菜单项的选择的时候,不会那么困难了)

}
=====================
QGraphicsView无法接收到一些widget传过来的消息的处理方法:
  bool event ( QEvent * event )
    {
        if(event->type()==QEvent::MouseButtonPress)
        {
            QMouseEvent *ke = static_cast<qmouseevent*>(event);
            qDebug()<<"Base Mouse Pressed...."<pos();
            QWidget::event(event);  //关键语句
            return true;
        }
        return QGraphicsView::event(event);
    }; 
==========================================================

基于Signal/Slot机制的接口写法:

MyInterface: public QObject{  //QObject子类都可以
    Q_OBJECT
public:
    explicit MyInterface(QObject* parent = 0);  //防止出现异常 显式
    virtual ~MyInterface(){}
    virtual void myFunc(int i) = 0; //纯虚函数
    //....
signals:
    void mySignal(int i);
    //....
public slots:
    virtual void mySlot(){//do nothing};
private:
    //...
}

MyImpl:public MyInterface{
    Q_OBJECT
public:
    MyImpl(parent = 0);
    virtual MyImpl(){};
    virtual void myFunc(int i){emit mySignal();};
public slots:
    void mySlot(){//my code};
}

MyImpl2:public MyInterface{
    Q_OBJECT
public:
    MyImpl(parent = 0);
    virtual MyImpl(){};
    virtual void myFunc(int i){emit mySignal();};
public slots:
    void mySlot(){//my code};
}

IMyInterface& createMyImpl1(parent = 0)
{
    return * new MyImpl1(parent);
}

IMyInterface& createMyImpl2(parent = 0)
{
    return * new MyImpl2(parent);

========================================================

析构函数 前一定要加 virtual

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