I can't load/save jpg image in Qt. I checked the imageformat folder in plugins folder and I found the dll/lib files related to this extension.
Here's the code I'm using:
void loadImages(){
QImage image;
QString folderName = "C:\\img-src\\";
bool isLoaded;
for(int i=1;i<3;i++){
QString fileName = folderName + QString::number(i) + ".jpg";
isLoaded = image.load(fileName,"JPG");
if(isLoaded){
qDebug() << "loaded";
}else{
qDebug() << "not loaded";
}
//Rest of the code
}
}
I found what the problem was.
I have to copy the imageformats folder next to the exe file of the program to enable loading/saving jpg files.
Related
I'm trying to create a text file by clicking on a button as following code, but I'm not getting.
QString local = "/local/flash/root";
QString name = " ProductionOrder.txt";
void page1000::on_pushButton_3_clicked()
{
QFile file(local+name);
if(!file.open(QFile::WriteOnly|QFile::Text)){
QMessageBox::warning(this,"ERROR","Error open file");
}
QTextStream output(&file);
QString text=ui->plainTextEdit->toPlainText();
output << text;
file.flush();
file.close();
}
what could be wrong with the code?
I am working with Qt 4.8
I don't know what to do
just put "/" at the end of the QString local
Like this: QString local = "/local/flash/root/";
I am trying to use the following code to open the existing file to append data at it's end:
void AddPharmacyForm::addInsertToFile(QString insert)
{
QFile inserts(":/new/prefix1/insertstatements.txt");
if(!inserts.exists())
qDebug() << "File does not exist";
if(inserts.isOpen())
qDebug() << "file is open";
if(inserts.open(QFile::ReadWrite | QFile::Text))
{
// Another workaround- could not open file with append flag
qDebug() << "im here!";
QString currentInserts;
QTextStream out(&inserts);
out >> currentInserts;
out << endl << insert;
inserts.close();
}
else
{
QMessageBox::information(this, tr("Error"), tr("Cannot add new pharmacy! "
"Please contact program designer."
));
qDebug() << "error code: " + QString::number(inserts.error());
return;
}
}
The output of this code is the QMessageBox with the error and in qDebug it produces following line:
"error code: 5"
It does not give notice about file not existing and file being open. I have also tried opening file with different flags: QFile::ReadWrite, QFile::append, QFile::WriteOnly and the same modes within QIODevice. The error code is still the same. When I am opening the file from another class, the file opens without errors (it is not an access error).
What might be causing this problem?
There's no support for writing into the resource system, whether implemented using Qt's resource system or native to the platform. Your application typically has no right to modify its own executable, or the application bundle, or its installation location - it'd be a security risk if it did since bugs in networking code could be easily exploited to infect your user's system. So what you're trying to do is just a bad idea.
Instead, store the modified resources in your application's data folder, and revert to reading from the resource if the file doesn't exist. It is also probably not very wise to append to a file if the file is small: such appends are not atomic and can partially fail, leaving the file corrupted. Using a QSaveFile is guaranteed to either completely succeed or to fail without modifying any data.
An example implementation follows. The src.close() is not necessary to close the file, as QFile will automatically close upon destruction, as it is a proper resource-managing C++ class. By closing it earlier we ensure minimal use of the file descriptor - a finite system resource.
// https://github.com/KubaO/stackoverflown/tree/master/questions/resource-bypass-43044268
#include <QtCore>
const char kInsertsFile[] = ":/insertstatements.txt";
QString toWritableName(const QString & qrcFileName) {
Q_ASSERT (qrcFileName.startsWith(":/"));
QFileInfo info(qrcFileName);
return
QStandardPaths::writableLocation(QStandardPaths::DataLocation)
+ info.path().mid(1) + '/' + info.fileName();
}
QString toReadableName(const QString & qrcFileName) {
Q_ASSERT (qrcFileName.startsWith(":/"));
auto writable = toWritableName(qrcFileName);
return QFileInfo(writable).exists() ? writable : qrcFileName;
}
bool setupWritableFile(QSaveFile & dst, QIODevice::OpenMode mode = {}) {
Q_ASSERT (dst.fileName().startsWith(":/"));
Q_ASSERT (mode == QIODevice::OpenMode{} || mode == QIODevice::Text);
QFile src(toReadableName(dst.fileName()));
dst.setFileName(toWritableName(dst.fileName()));
if (!src.open(QIODevice::ReadOnly | mode))
return false;
auto data = src.readAll();
src.close(); // Don't keep the file descriptor tied up any longer.
QFileInfo dstInfo(dst.fileName());
if (!dstInfo.dir().exists() && !QDir().mkpath(dstInfo.path()))
return false;
if (!dst.open(QIODevice::WriteOnly | mode))
return false;
return dst.write(data) == data.size();
}
bool addInsertToFile(const QString & insert) {
QSaveFile file(kInsertsFile);
if (!setupWritableFile(file, QIODevice::Text))
return false;
if (true) {
// Alternative 1
QTextStream s(&file);
s << insert << '\n';
} else {
// Alternative 2
file.write((insert + '\n').toLocal8Bit());
}
return file.commit();
}
QStringList readInserts() {
QFile file(toReadableName(kInsertsFile));
if (!file.open(QIODevice::ReadOnly))
return {};
return QString::fromLocal8Bit(file.readAll()).split('\n', QString::SkipEmptyParts);
}
int main(int argc, char ** argv) {
QCoreApplication app{argc, argv};
app.setApplicationName("resource-bypass-42044268");
qDebug() << "Original Inserts:" << readInserts();
auto rc = addInsertToFile("NewInsert");
qDebug() << "Modification status:" << rc;
qDebug() << "Current Inserts:" << readInserts();
}
When you use the Qt Resource System (qrc files) to add files for your project, they are compiled directly into the binary of your application, so are therefore readonly. As the documentation states: -
Resource data can either be compiled into the binary and thus accessed immediately in application code, or a binary resource can be created and at a later point in application code registered with the resource system.
And...
Currently, Qt always stores the data directly in the executable, even on Windows, macOS, and iOS, where the operating system provides native support for resources. This might change in a future Qt release.
I am downloading an ".apk" file from a Url with Get method.
The file successfully donwload on my disk from the server.
I actually want to add a progressbar to my program. THE problem is : I can show the bytesReceived but I can't show the totalBytes of the file I am downloading (ContentLenth). How can I get it please from the server.
Here is what i get on my qDebug while downloading:
3498 of -1
799062 of -1
1923737 of -1
3037550 of -1
3200231 of 3200231
Here is my code:
void DownloadApk::LaunchDownload()
{
QNetworkProxy proxy;
proxy.setType(QNetworkProxy::HttpProxy);
proxy.setHostName("proxy");
proxy.setPort(8080);
QNetworkProxy::setApplicationProxy(proxy);
QUrl url("I put my Url here");
QNetworkRequest request(url);
_file = new QFile("C:/Users/Desktop/testdownload/downloadedFile.apk");
_file->open(QIODevice::WriteOnly);
QNetworkAccessManager *_manager= new QNetworkAccessManager;
_reply = _manager->get(request);// Manager is my QNetworkAccessManager
_file->write(_reply->readAll());
connect(_reply, SIGNAL(error(QNetworkReply::NetworkError)),
this, SLOT(error(QNetworkReply::NetworkError)));
connect(_reply, SIGNAL(downloadProgress(qint64, qint64)),
this, SLOT(updateProgress(qint64, qint64)));
connect(_reply, SIGNAL(finished()),
this, SLOT(finished()));
}
void DownloadApk::error(QNetworkReply::NetworkError err)
{qDebug() << err;
// Manage error here.
_reply->deleteLater();
}
void DownloadApk::updateProgress(qint64 read, qint64 total)
{
qDebug() << read <<"of"<<total ;
QByteArray b = _reply->readAll();
QDataStream out(_file);
out << b;
}
void DownloadApk::finished()
{
QMessageBox::information(this, tr("Complete"), tr("Successfully Downloaded"));
// Done
_reply->deleteLater();
_file->close();
// probably delete the file object too
}
I fixed the problem. Actually it was not a QT problem. This Qt code works correctly.
The probleme was from the server that wasn't sending ContentLenth on the header of the reply.
I have a code:
int actualSize = 8;
QFile tableFile("C:\\Users\\Ms\\Documents\\L3\\table"+QString::number(actualSize)+".txt");
QTextStream in(&tableFile);
QString oneLine;
oneLine.append(in.readAll());
if(tableFile.exists())
{
messageLabel->setText(oneLine);
}else
{
messageLabel->setText("Not open");
}
In the C:\Users\Ms\Documents\L3\ folder, I have a "table8.txt" file. But the messageLabel (which is a QLabel) will have a "Not open" text, oneLine is empty, tableFile.exists() is false, and I got a device not open warning/error.
I tried relative path, like
QFile tableFile("table"+QString::number(actualSize)+".txt");
But none of the methods I come up with was good.
You should be able to use / separators for all QFile-related paths. Open the file before you read it and close it when done.
int actualSize = 8;
QFile tableFile("C:/Users/Ms/Documents/L3/table"+QString::number(actualSize)+".txt");
if(tableFile.exists() && tableFile.open(QIODevice::ReadOnly | QIODevice::Text))
{
QTextStream in(&tableFile);
QString oneLine;
oneLine.append(in.readAll());
messageLabel->setText(oneLine);
tableFile.close();
} else
{
messageLabel->setText("Not open");
}
I am trying to read data from Multiple files in Qt.
This how I am doing it:
void MainWindow::on_pushButton_3_clicked()
{
QString path = "C:/MyDevelopment/readfiles";
QDir dir(path);
QStringList filters;
filters << "*.txt";
foreach ( QString fileName, dir.entryList(filters, QDir::Files) )
{
QFile readFile(fileName);
if(!readFile.open(QIODevice::ReadOnly | QIODevice::Text ) )
{
qDebug("Failed to read file.....");
//return ;
}
QTextStream in(&fileName);
while (!in.atEnd())
{
QString line = in.readLine();
qDebug() << line;
}
}
it is always going in failed to open. what i am doing wrong here??
in mentioned directory all files are .txt files.