I have got FFmpeg compiled using MSYS2. I have a strange issue that appeared only recently.the app crashes.
This is my main file:
#include "mainwindow.h"
#include <QApplication>
#include <QDebug>
extern "C" {
#include <libavdevice/avdevice.h>
#include <libavformat/avformat.h>
#include <libavutil/avutil.h>
#include <libavcodec/avcodec.h>
}
int main(int argc, char *argv[])
{
//qDebug() << av_version_info();
// avdevice_register_all();
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
The program runs but crashes if I call 'avdevice_register_all()' and others FFmpeg functions，but only call 'av_version_info()' is runs, not crashes.
I don't really know how to solve this?
I have already tried to use google solving the problem,but no result.
Related
I make a QT console program.
I want to show every command by new window.
How could I do that ??
main.cpp
I use system is win10 with QT.
#include <QCoreApplication>
#include <QDebug> //在文字視窗輸出文字功能函式
#include <QDir> //搜尋資料夾功能函式
#include <QFileInfo> //顯示檔案資訊
#include <QString> //字串函式
#include <QStringList> //字串陣列函式
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QDir mDir; //設定資料夾位置
qDebug() << mDir.exists(); //輸出確定是否有mDir資料夾
QString command = "frtomem -p WnaYooAQ ";
foreach(QFileInfo mitm, mDir.entryInfoList(Qfilter)) //列出所有資料夾中篩選的檔案內容
{
qDebug() << command << mitm.fileName();
}
return a.exec();
}
I just can show it by one console window.
can't separete it.
I'm trying to set the LocalStorage location (sqlite db) for my QML application but once i rebuild and run the application i still can't see the subfolder, INI file and the sqlite DB created on the desired location (in a subfolder within the resources folder). Here is what's in my main file.
Appreciate any one could pint what's I'm doing wrong here?
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QString>
#include <QDebug>
#include <QDir>
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
//engine.setOfflineStoragePath("qrc:/");
auto offlineStoragePath = QUrl::fromLocalFile(engine.offlineStoragePath());
engine.rootContext()->setContextProperty("offlineStoragePath", offlineStoragePath);
QString customPath = "qrc:/OffLineStorage";
QDir dir;
if(dir.mkpath(QString(customPath))){
qDebug() << "Default path >> "+engine.offlineStoragePath();
engine.setOfflineStoragePath(QString(customPath));
qDebug() << "New path >> "+engine.offlineStoragePath();
}
return app.exec();
}
By looking at the code snippet in your question, everything looks fine.
Anyway, you should verify if the following line actually returns true as you expect:
dir.mkpath(QString(customPath)
If no, the body of the if statement isn't executed in any case, thus setOfflineStoragePath is never invoked.
As a hint, using qrc:/OffLineStorage as a path for your storage doesn't seem to be a good idea. I'm not sure it will work once in the production environment (to be checked, it sounds strange, but it could work).
Try use engine.setOfflineStoragePath before engine.load.
Using qrc:/OffLineStorage as a path for your storage doesn't seem to
be a good idea. I'm not sure it will work once in the production
environment
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QString>
#include <QDebug>
#include <QDir>
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
QString customPath = "qrc:/OffLineStorage";
QDir dir;
if(dir.mkpath(QString(customPath))){
qDebug() << "Default path >> "+engine.offlineStoragePath();
engine.setOfflineStoragePath(QString(customPath));
qDebug() << "New path >> "+engine.offlineStoragePath();
}
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
engine.clearComponentCache();
if (engine.rootObjects().isEmpty())
return -1;
return app.exec();
}
What is used to open urls with QDesktopServices::openUrl(...)?
xdg-open, kopen, selmademachanism or a mix of them? I ask because it fails on a scheme where xdg-open does not.
Edit: okay its getting even more curious: The missing scheme works in debug mode, but not in release mode...
Example code:
#include <QApplication>
#include <QDesktopServices>
#include <QUrl>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QDesktopServices::openUrl(QUrl("tg://resolve?domain=imagebot"));
}
.h
#include <QObject>
#include <QDebug>
class MyClass : public QObject
{
Q_OBJECT
public:
Q_INVOKABLE void cppMethod (const QString &msg)
{
qDebug() << "Called the C++ method with" << msg;
}
public slots:
void cppSlot (int number)
{
qDebug() << "Called the C++ slot with" << number;
}
};
.cpp
#include <QtCore/QCoreApplication>
#include <QDeclarativeEngine>
#include <QDeclarativeComponent>
#include <QDeclarativeContext>
#include <QDeclarativeView>
#include <QVariant>
#include <QMetaObject>
#include "cppFromQml.h"
int main (int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QDeclarativeView view;
return a.exec();
}
This results in segmentation fault. What's the way out?
Qt: 4.8.1
note that you're not using MyClass, and - just my guess - a declarative view will need a QApplication to properly run.
To better understand, I created a project, dumped almost all away (just kept the .pro, where I added qt += declarative), and changed a bit your code as follow:
#include <QApplication>
#include <QDeclarativeEngine>
#include <QDeclarativeComponent>
#include <QDeclarativeContext>
#include <QDeclarativeView>
#include <QVariant>
#include <QMetaObject>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QDeclarativeView view;
view.show();
return a.exec();
}
now it runs and display an empty view, as expected...
I am trying to use the libfprint in my Qt application
#include <QtGui/QApplication>
#include "mainwindow.h"
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <libfprint/fprint.h>
int main(int argc, char *argv[])
{
int r = 1;
struct fp_dscv_dev *ddev;
struct fp_dscv_dev **discovered_devs;
struct fp_dev *dev;
struct fp_print_data *data;
r = fp_init();
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
Compiling throws this error
/concept/main.cpp:31: undefined reference to `fp_init()'
I have been battling with this for a while now. Any idea what I can do to get past this point? Thanks in advance!
It's a problem with your linker - it cannot find necessary libraries. Did you pass necessary linker switches (something like -lfoo) instructing it to link with library you are trying to use?