我终于找到了一个路径文件QFile会接受使用QFile.exist()和健康剂量的反复试验。
我想知道为什么以下有效:
#include <QFile>
#include <QByteArray>
#include <QJsonObject>
#include <QJsonDocument>
QString path = QDir::currentPath(); // Get current dir
path.append("/noteLibrary.json");
QFile file(path); // Give QFile current dir + path to file
if (!file.exists()) { // Check to see if QFile found the file at given file_path
qDebug() << "NO FILE HERE";
}
qDebug() << path; // See what path was finally successful
file.open(QIODevice::ReadOnly); // Continue parsing document to confirm everything else is functioning normally.
QByteArray rawData = file.readAll();
// Parse document
QJsonDocument doc(QJsonDocument::fromJson(rawData));
// Get JSON object
QJsonObject json = doc.object();
// Access properties
qDebug() << json["die"].toString(); // Should output "280C4"
成功输出:
"/home/pi/noteLibrary.json"
"280C4"
但以下不起作用:
#include <QFile>
#include <QByteArray>
#include <QJsonObject>
#include <QJsonDocument>
QFile file("/home/pi/noteLibrary.json"); // Give QFile current dir + path to file
if (!file.exists()) { // Check to see if QFile found the file at given file_path
qDebug() << "NO FILE HERE";
}
//qDebug() << path; // See what path was finally successful
file.open(QIODevice::ReadOnly); // Continue parsing document to confirm everything else is functioning normally.
QByteArray rawData = file.readAll();
// Parse document
QJsonDocument doc(QJsonDocument::fromJson(rawData));
// Get JSON object
QJsonObject json = doc.object();
// Access properties
qDebug() << json["die"].toString(); // Should output "280C4"
错误输出:
NO FILE HERE
QIODevice::read (QFile, "/home/pi/Desktop/noteLibrary.json"): device not open
""
为什么QFile会以不同方式对待这些?这是QString格式问题吗?或者我将这个远程部署到Raspberry Pi 3的事实可能是罪魁祸首?
答案 0 :(得分:0)
无论上面的代码出了什么问题,使用下面给出QFile的代码,绝对路径对使用currentPath()创建QString同样有效。我一定有别的错,我的错误!
noteLibrary.json
{"note": [{
"profile": "C4",
"die": "280C4",
"pressure": 800,
"position": 10000
},
{
"profile": "CC4",
"die": "2280C4",
"pressure": 8800,
"position": 110000
}
],
"test": {
"profile": "CCC4",
"die": "22280C4",
"pressure": 88800,
"position": 1110000
}
}
main.cpp 摘录
QFile file("/home/pi/noteLibrary.json");
if (!file.exists()) qDebug() << "NO FILE FOUND";
file.open(QIODevice::ReadOnly);
QByteArray rawData = file.readAll();
QJsonDocument doc(QJsonDocument::fromJson(rawData)); // Parse document
QJsonObject jObj = doc.object(); // Get JSON object
qDebug() << jObj["test"];
应用程序输出
QJsonValue(object,QJsonObject({"die":"22280C4","position":1110000,"pressure":88800,"profile":"CCC4"}))
奇怪的是,它按字母顺序显示属性值,而不是文档中列出的顺序。