I'm trying to read a text file and display the contents in a QPlainTextEdit. Please can you point out what I'm doing wrong:
QFile jsonFile("data.json");
if (!jsonFile.open(QIODevice::ReadOnly | QIODevice::Text))
{
qDebug() << "Failed to open file";
qDebug() << jsonFile.errorString();
return;
}
else
{
qDebug() << "File opened";
} //It returns that the file opened successfully
qDebug() << "File Exists?: " << jsonFile.exists(); //Yep, it exists.
QTextStream outStream(&jsonFile);
QString textString = outStream.readAll();
qDebug() << "Text string: " << textString; //textString is empty! ""
ui->fileToPost->setPlainText(textString); //fileToPost is the QPlainTextEdit
jsonFile.close();
If I do something like
QString textString = "The cat sat on the mat";
it displays fine. The problem is that nothing is being read from the stream (or maybe the file).
Try to check file's absolute path, probably it is not where, you expect it: qDebug()<<QFileInfo("data.json").absoluteFilePath();
Related
I'm trying to read in a file of trace addresses (each on their own line) and append to the front of each. This input file is intended to be the engine of a cache emulator i'm trying to build. I am having issues reading the file in without getting into an infinite loop. When I change the do-while to run on a false condition, I get the proper output for just the do segment. Therefore, I know I'm running into an infinite loop issue with how I worded my while segment. Maybe i'm fatigued and can't see the issue with this function:
void MainWindow::readFile(){
infoLabel->setText(tr("Invoked <b>File|Open</b>"));
QString filename="trace.txt";
QString path = QDir::currentPath();
QFile file("//Users//nathan1324//Desktop//trace.txt");
//file.open(QIODevice::ReadOnly);
if(!file.exists()){
qDebug() << "File cannot be found "<<filename;
qDebug() << " " << path;
}else{
qDebug() << filename<<" Opening...";
}
QString line;
textEdit->clear();
if (file.open(QIODevice::ReadOnly | QIODevice::Text)){
QTextStream stream(&file);
do {
line = stream.readLine();
textEdit->setText(textEdit->toPlainText()+"0x"+line+"\n");
qDebug() << "line: "<<line;
} while (!line.isNull());
}
file.close();
}
Any suggestions of an alternative way to write this function?
To add items use the append function of QTextEdit:
void QTextEdit::append(const QString & text)
Appends a new paragraph with text to the end of the text edit.
Note: The new paragraph appended will have the same character format
and block format as the current paragraph, determined by the position
of the cursor.
To iterate through the QTextStream atEnd()
bool QTextStream::atEnd() const
Returns true if there is no more data to be read from the QTextStream;
otherwise returns false. This is similar to, but not the same as
calling QIODevice::atEnd(), as QTextStream also takes into account its
internal Unicode buffer.
Code:
void MainWindow::readFile(){
infoLabel->setText(tr("Invoked <b>File|Open</b>"));
QString filename = "trace.txt";
QString path = QDir::currentPath();
QFile file("//Users//nathan1324//Desktop//trace.txt");
if(!file.exists()){
qDebug() << "File cannot be found "<<filename;
qDebug() << " " << path;
return;
}
QString line;
textEdit->clear();
if (!file.open(QIODevice::ReadOnly | QIODevice::Text)){
qDebug() << "Could not open file" << filename;
return;
}
qDebug() << filename<<" Opening...";
QTextStream stream(&file);
while (!stream.atEnd()) {
line = stream.readLine();
if(!line.isNull()){
textEdit->append("0x"+line);
qDebug() << "line: "<<line;
}
}
file.close();
}
Use atEnd to detect the end of a stream:
bool QTextStream::atEnd() const
Returns true if there is no more data to be read from the QTextStream;
otherwise returns false. This is similar to, but not the same as
calling QIODevice::atEnd(), as QTextStream also takes into account its
internal Unicode buffer.
while (!stream.atEnd()) {
line = stream.readLine();
textEdit->setText(textEdit->toPlainText()+"0x"+line+"\n");
qDebug() << "line: "<<line;
}
I have this file which is located in my C drive, I know it exists. When I access it with QFile.exists() it returns false, however it still opens the file and writes to it, I just cant read it. I've been working on this for a while and cannot find a solution, any suggestions are appreciated.
QFile tmpfile("C:/file.txt");
QString tmpcontent;
if(!QFile::exists("C:/file.txt"))
qDebug() << "File not found"; // This is outputted
if (tmpfile.open(QIODevice::ReadWrite | QIODevice::Truncate)) {
QTextStream stream(&tmpfile);
stream << "test"; //this is written
tmpcontent = tmpfile.readAll(); // this returns nothing
}
If file is not exist it will be created by open because you do it in write mode.
readAll function return all remaining data from device, since you just write something you are currently at the end of a file, and there is no data, try to seek( 0 ) to return to the beginnig of a file and then use readAll.
qDebug() << "File exists: " << QFile::exists("text.txt");
QFile test( "text.txt" );
if ( test.open( QIODevice::ReadWrite | QIODevice::Truncate ) ){
QTextStream str( &test );
str << "Test string";
qDebug() << str.readAll();
str.seek( 0 );
qDebug() << str.readAll();
test.close();
}else{
qDebug() << "Fail to open file";
}
As I can see from your code you need that file as a temporary, in such case I suggest to use QTemporaryFile, it will be created in temp directory (I belive there will be no problem with permissions), with unique name and will be auto deleted in object dtor.
I have my slot being called whenever someone clicks the link and I know the file is there because I can retrieve the file name and the amount of bytes the file is just not sure how to s ave it after I call the QFileDialog::getSaveFileName? I know that gives me the name of the file if the user decides to change it but how do I get the location they decide to save it in and then write it to that location.
NB: The file they will download is a word doc if that makes any difference?
void MainWindow::unsupportedContent(QNetworkReply *reply) {
qDebug() << "Left click - download!";
qDebug() << "Bytes to download: " << reply->bytesAvailable();
QString str = reply->rawHeader("Content-Disposition");
QString end = str.mid(21);
end.chop(1);
qDebug() << "string: " << end;
qDebug() << "File name: " << reply->rawHeader("Content-Disposition");
qDebug() << "File type: " << reply->rawHeader("Content-Type");
QString defaultFileName = QFileInfo(end).fileName();
QString fileName = QFileDialog::getSaveFileName(this, tr("Save File"), defaultFileName);
if (fileName.isEmpty()) return;
QFile *file = new QFile(fileName);
file->open(fileName);
file->write(reply->read(reply->bytesAvailable()));
file->close();
}
today i explained it on another post so i will link that post here : Post
i can tell you that you have only to implement a slot that write into the file you created. and call it when readyRead() signal is emitted.
I'm currently create an apps in Meego using QML and JS on most of the part. and now I stumbled upon a problem.
From javascript I want to call a C++ function to read text file, parse it, and then return an array of the parsing result.
so I create a Q_INVOKABLE function called parse() and call it through javascript
function parse() {
var myArray = new Array();
myArray = parser.parse("/home/user/MyDocs/angklungtext.txt")
if(myArray === undefined){
console.log("null found");
}
for(var i = 0; i < myArray.length; i++){
console.log(myArray[i][0] + "," + myArray[i][1])
}
}
and here is the parse function in C++
QVariantList* QMLParser::parse(QString filename)
{
qDebug() << "start debugging";
qDebug() << filename;
qDebug() << QDir::currentPath();
QDir dir;
qDebug()<< dir.absoluteFilePath(filename);
QFile file(filename);
if(!file.exists())
{
qDebug() << "File: " << file.fileName() << "tidak ditemukan";
return NULL;
}
if(!file.open(QIODevice::ReadOnly | QIODevice::Text))
{
qDebug() << "Tidak dapat membuka file" << file.fileName() << "untuk ditulis";
return NULL;
}
QTextStream stream(&file);
QVariantList* myList = new QList<QVariant>;
while(!stream.atEnd())
{
QString line = stream.readLine();
qDebug() << line.trimmed();
QStringList lineList = line.split(":");
myList->append(lineList);
}
file.close();
return myList;
}
sadly.
when I try to run it it giving a result like this
start debugging
"/home/user/MyDocs/angklungtext.txt"
"/home/developer"
"/home/user/MyDocs/angklungtext.txt"
"1:1000"
"4:2000"
"5:3000"
"2:4000"
null found
file:///opt/memoryreader/qml/memoryreader/myjs.js:8: TypeError: Result of expression 'myArray' [undefined] is not an object.
looks like the C++ parse function successfully parsing the file. it can read it and it can save it into the QVariantList.
but after it return the result into javascript myArray still [undefined].
is there something wrong with the conversion?
Just simplify the C++ side like this :
QVariant QMLParser::parse(QString filename)
{
QStringList myList;
qDebug() << "start debugging";
qDebug() << filename;
qDebug() << QDir::currentPath();
QDir dir;
qDebug() << dir.absoluteFilePath(filename);
QFile file(filename);
if(!file.exists()) {
qDebug() << "File: " << file.fileName() << "tidak ditemukan";
return NULL;
}
if(!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
qDebug() << "Tidak dapat membuka file" << file.fileName() << "untuk ditulis";
return NULL;
}
QTextStream stream(&file);
while(!stream.atEnd()) {
QString line = stream.readLine();
qDebug() << line.trimmed();
myList << line.trimmed().split(":");
}
file.close();
return QVariant::fromValue(myList);
}
And it should work !
Just remember, QML must see a QVariant, even if a QList is wrapped inside it, and Qt is able to convert most of its base types to QVariant using QVariant::fromValue(T) so use it extensively.
Oh and BTW a QVariant is reference not pointer.
Haven't done this myself, so I'm just thinking out loud. But I note that you're returning a pointer to a QVariantList...which looks suspect. (Also: if you new, then who would do the delete?)
Have you tried returning it by value?
I'm using Qt to develop my C++ application using QML as well.
Here's my code
QFile inputFile("data.txt");
//QFile inputFile("/:data.txt");
qDebug() << "Hello:";
if (!inputFile.open(QIODevice::ReadOnly | QIODevice::Text))
{
qDebug() << "Wasn't ready:";
}
else{
qDebug() << "Txt file ready:";
QTextStream in(&inputFile);
while ( !in.atEnd() )
{
QString line = in.readLine();
qDebug() << "message: " << line;
}
}
I was wondering why it doesn't work. The console always prints "Wasn't ready".
Please help.
In the error handling block where you do qDebug() << "Wasn't ready:"; you should call inputFile.error() and print out the returned value to get more details of what went wrong.
It might also be an idea to start the program with printing out the current directory, to make sure that the file is searched for in the correct location.