晚上好，
我使用了这个教程http://codingexodus.blogspot.de/2013/01/getting-started-with-qwt.html，并将此[http://de.wikibooks.org/wiki /Qt_für_C％2B％2B-Anfänger：_Qwt_nutzen 2作为起点。
这里qwt用于main.cpp：
#include <qwt_plot_curve.h>
#include <qwt_plot.h>
#include <qapplication.h>
int main(int argc, char **argv)
{
QApplication a(argc, argv);
double x[101];
double y[101];
for ( int i = 0; i < 101; i++ ) {
x[i] = i / 10.0;
y[i] = sin(x[i]);
}
QwtPlot plot;
QwtPlotCurve *curve = new QwtPlotCurve();
curve->setRawSamples(x, y, 101);
curve->attach(&plot);
plot.show();
return a.exec();
}
当我尝试（通过复制和粘贴以进行测试时，如果我正确地包含了库），我保持接收的两个站点的代码
QWidget：必须在QPaintDevice之前构建QApplication
好的，所以我应该在创建Widget之前创建一个Application。 但是，为了安全起见，我决定测试将qwt部分放入mainwindow .cpp文件中。但仍然没有成功。
在应用程序输出下方。似乎qwt和qt之间存在一些冲突...（当我不使用qwt时不会出现。）
Starte /Users/axel/Programmierung/Qt/Qwt2/build-Qwt2-Desktop-Debug/Qwt2.app/Contents/MacOS/Qwt2...
objc[6955]: Class QCocoaPageLayoutDelegate is implemented in both /usr/local/lib/QtGui.framework/Versions/4/QtGui and /usr/local/Cellar/qt5/5.3.2/lib/QtPrintSupport.framework/Versions/5/QtPrintSupport. One of the two will be used. Which one is undefined.
objc[6955]: Class QCocoaPrintPanelDelegate is implemented in both /usr/local/lib/QtGui.framework/Versions/4/QtGui and /usr/local/Cellar/qt5/5.3.2/lib/QtPrintSupport.framework/Versions/5/QtPrintSupport. One of the two will be used. Which one is undefined.
objc[6955]: Class QCocoaApplicationDelegate is implemented in both /usr/local/lib/QtGui.framework/Versions/4/QtGui and /usr/local/Cellar/qt5/5.3.2/plugins/platforms/libqcocoa.dylib. One of the two will be used. Which one is undefined.
objc[6955]: Class QNSApplication is implemented in both /usr/local/lib/QtGui.framework/Versions/4/QtGui and /usr/local/Cellar/qt5/5.3.2/plugins/platforms/libqcocoa.dylib. One of the two will be used. Which one is undefined.
objc[6955]: Class QCocoaMenuLoader is implemented in both /usr/local/lib/QtGui.framework/Versions/4/QtGui and /usr/local/Cellar/qt5/5.3.2/plugins/platforms/libqcocoa.dylib. One of the two will be used. Which one is undefined.
objc[6955]: Class QNSOpenSavePanelDelegate is implemented in both /usr/local/lib/QtGui.framework/Versions/4/QtGui and /usr/local/Cellar/qt5/5.3.2/plugins/platforms/libqcocoa.dylib. One of the two will be used. Which one is undefined.
objc[6955]: Class QNSImageView is implemented in both /usr/local/lib/QtGui.framework/Versions/4/QtGui and /usr/local/Cellar/qt5/5.3.2/plugins/platforms/libqcocoa.dylib. One of the two will be used. Which one is undefined.
objc[6955]: Class QNSStatusItem is implemented in both /usr/local/lib/QtGui.framework/Versions/4/QtGui and /usr/local/Cellar/qt5/5.3.2/plugins/platforms/libqcocoa.dylib. One of the two will be used. Which one is undefined.
objc[6955]: Class QNSMenu is implemented in both /usr/local/lib/QtGui.framework/Versions/4/QtGui and /usr/local/Cellar/qt5/5.3.2/plugins/platforms/libqcocoa.dylib. One of the two will be used. Which one is undefined.
QWidget: Must construct a QApplication before a QPaintDevice
Das Programm ist abgestürzt.
/Users/axel/Programmierung/Qt/Qwt2/build-Qwt2-Desktop-Debug/Qwt2.app/Contents/MacOS/Qwt2 ist abgestürzt
qwt2.pro
#-------------------------------------------------
#
# Project created by QtCreator 2014-12-06T23:33:01
#
#-------------------------------------------------
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = Qwt2
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
win32:CONFIG(release, debug|release): LIBS += -L$$PWD/../../../../../../usr/local/Cellar/qwt/6.1.1/lib/release/ -lqwt
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/../../../../../../usr/local/Cellar/qwt/6.1.1/lib/debug/ -lqwt
else:mac: LIBS += -F$$PWD/../../../../../../usr/local/Cellar/qwt/6.1.1/lib/ -framework qwt
else:unix: LIBS += -L$$PWD/../../../../../../usr/local/Cellar/qwt/6.1.1/lib/ -lqwt
INCLUDEPATH += $$PWD/../../../../../../usr/local/Cellar/qwt/6.1.1/lib/qwt.framework/Versions/6/Headers
DEPENDPATH += $$PWD/../../../../../../usr/local/Cellar/qwt/6.1.1/lib/qwt.framework/Versions/6/Headers
的main.cpp
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <qwt_plot_curve.h>
#include <qwt_plot.h>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
double x[101];
double y[101];
for ( int i = 0; i < 101; i++ ) {
x[i] = i / 10.0;
y[i] = sin(x[i]);
}
QwtPlot plot;
// QwtPlotCurve *curve = new QwtPlotCurve();
// curve->setRawSamples(x, y, 101);
// curve->attach(&plot);
// plot.show();
}
MainWindow::~MainWindow()
{
delete ui;
}
（请注意，我在QwtPlot plot;之前移除评论时会立即复制有关QApplication和QPaintDevice的错误。
2014年12月7日的其他信息 请注意，错误消息提示不同的Qt版本：
objc[8714]: Class QNSMenu is implemented in both /usr/local/lib/QtGui.framework/Versions/4/QtGui and /usr/local/Cellar/qt5/5.3.2/plugins/platforms/libqcocoa.dylib. One of the two will be used. Which one is undefined.
我没有安装Qt4（知情）
假设： Homebrew安装了Qt4。
所以我通过brew info qwt查看了。
答案：==> Dependencies
Required: qt ✔
下一步：brew info qt
答：
qt: stable 4.8.6 (bottled), HEAD
http://qt-project.org/
/usr/local/Cellar/qt/4.8.6 (2790 files, 122M) *
Built from source
好的，所以自制软件为qwt安装了Qt4。
我依稀记得在5.1或5.2中Qt将一些QGui或QApplication内容移动到另一个头...所以如果qwt现在从Qt5中选择一个头（请记住：错误消息说这是未定义的行为）而不是Qt4，可以这解释了错误发生的原因？
好的，到现在为止，我使用相同的源代码打开了一个新项目，但使用的是qt 4.8.6。 没有错误消息。 也没有情节，但这似乎是另一个问题。