Question

我需要在模拟屏幕上显示一个字符串。为此，我应该从现有的Filename.txt / Filename.csv文件中读取文本。 text参数更新，如下面的代码所示。我需要从文本文件中访问该字符串并在MarqueeText元素中使用它。访问的字符串应在 MarqueeText 元素的 text 字段中使用。

MarqueeText {
     id:scrolltext
     width: 255
     height: 48
     anchors.verticalCenter: parent.horizontalCenter
     text:   //i need to access the string in text file to be displayed
}

请帮我解决这个问题。谢谢。

Answer 1

按照Wiki页面阅读有关使用QML访问文件的信息。诺基亚维基论坛http://web.archive.org/web/20150227025348/http://developer.nokia.com/community/wiki/Reading_and_writing_files_in_QML

要点：

创建自定义QML类型FileIO：

<强> fileio.h

#ifndef FILEIO_H
#define FILEIO_H

#include <QObject>

class FileIO : public QObject
{
    Q_OBJECT

public:
    Q_PROPERTY(QString source
               READ source
               WRITE setSource
               NOTIFY sourceChanged)
    explicit FileIO(QObject *parent = 0);

    Q_INVOKABLE QString read();
    Q_INVOKABLE bool write(const QString& data);

    QString source() { return mSource; };

public slots:
    void setSource(const QString& source) { mSource = source; };

signals:
    void sourceChanged(const QString& source);
    void error(const QString& msg);

private:
    QString mSource;
};

#endif // FILEIO_H

<强> fileio.cpp

#include "fileio.h"
#include <QFile>
#include <QTextStream>

FileIO::FileIO(QObject *parent) :
    QObject(parent)
{

}

QString FileIO::read()
{
    if (mSource.isEmpty()){
        emit error("source is empty");
        return QString();
    }

    QFile file(mSource);
    QString fileContent;
    if ( file.open(QIODevice::ReadOnly) ) {
        QString line;
        QTextStream t( &file );
        do {
            line = t.readLine();
            fileContent += line;
         } while (!line.isNull());

        file.close();
    } else {
        emit error("Unable to open the file");
        return QString();
    }
    return fileContent;
}

bool FileIO::write(const QString& data)
{
    if (mSource.isEmpty())
        return false;

    QFile file(mSource);
    if (!file.open(QFile::WriteOnly | QFile::Truncate))
        return false;

    QTextStream out(&file);
    out << data;

    file.close();

    return true;
}

注册新的QML类型：

#include "fileio.h"

Q_DECL_EXPORT int main(int argc, char *argv[])
{
   ...
    qmlRegisterType<FileIO, 1>("FileIO", 1, 0, "FileIO");
    ...
}

实际QML使用情况：

import QtQuick 1.1
import FileIO 1.0

Rectangle {
    width: 360
    height: 360
    Text {
        id: myText
        text: "Hello World"
        anchors.centerIn: parent
    }

    FileIO {
        id: myFile
        source: "my_file.txt"
        onError: console.log(msg)
    }

    Component.onCompleted: {
        console.log( "WRITE"+ myFile.write("TEST"));
        myText.text =  myFile.read();
    }
}

从qml中的.txt或.csv文件中读取一行（Qt Quick）

1 个答案: