在Qt5中创建、读取和写入JSON文件的完整指南

本文主要是介绍在Qt5中创建、读取和写入JSON文件的完整指南，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

Qt5 提供了一个非常方便的JSON解析器，使得在C++中处理JSON数据变得非常简单。本文将详细介绍如何在Qt5中创建、读取和写入JSON文件。

读取JSON文件的示例

假设我们有一个名为test.json的JSON文件，内容如下：

{"appDesc": {"description": "SomeDescription","message": "SomeMessage"},"appName": {"description": "Home","message": "Welcome","imp": ["awesome", "best", "good"]}
}

我们可以通过以下代码读取这个JSON文件：

void readJson() {QString val;QFile file;file.setFileName("test.json");file.open(QIODevice::ReadOnly | QIODevice::Text);val = file.readAll();file.close();qWarning() << val;QJsonDocument d = QJsonDocument::fromJson(val.toUtf8());QJsonObject sett2 = d.object();QJsonValue value = sett2.value(QString("appName"));qWarning() << value;QJsonObject item = value.toObject();qWarning() << tr("QJsonObject of description: ") << item;// 获取字符串值并转换为字符串qWarning() << tr("QJsonObject[appName] of description: ") << item["description"];QJsonValue subobj = item["description"];qWarning() << subobj.toString();// 获取数组值并转换为字符串qWarning() << tr("QJsonObject[appName] of value: ") << item["imp"];QJsonArray test = item["imp"].toArray();qWarning() << test[1].toString();
}

执行上述代码后，控制台输出如下：

QJsonValue(object, QJsonObject({"description": "Home","imp": ["awesome","best","good"],"message": "Welcome"}) )
"QJsonObject of description: " QJsonObject({"description": "Home","imp": ["awesome","best","good"],"message": "Welcome"})
"QJsonObject[appName] of description: " QJsonValue(string, "Home")
"Home"
"QJsonObject[appName] of value: " QJsonValue(array, QJsonArray(["awesome","best","good"]))
"best"

解析JSON字符串的示例

我们也可以将一个JSON字符串解析为JSON对象：

void readJsonFromString() {QString jsonString = R"({"appDesc": {"description": "SomeDescription","message": "SomeMessage"},"appName": {"description": "Home","message": "Welcome","imp": ["awesome", "best", "good"]}})";QJsonDocument d = QJsonDocument::fromJson(jsonString.toUtf8());QJsonObject sett2 = d.object();QJsonValue value = sett2.value(QString("appName"));qWarning() << value;QJsonObject item = value.toObject();qWarning() << tr("QJsonObject of description: ") << item;qWarning() << tr("QJsonObject[appName] of description: ") << item["description"];QJsonValue subobj = item["description"];qWarning() << subobj.toString();qWarning() << tr("QJsonObject[appName] of value: ") << item["imp"];QJsonArray test = item["imp"].toArray();qWarning() << test[1].toString();
}

创建和写入JSON文件的示例

下面的代码展示了如何创建一个带有结构的JSON文件：

void createJson() {QFile file(QDir::homePath() + "/1.json");if(!file.open(QIODevice::ReadWrite)) {qDebug() << "File open error";} else {qDebug() << "File open!";}// 清空文件内容file.resize(0);// 创建JSON数组，并写入到文件QJsonArray jsonArray;for(int i = 0; i < 10; i++) {QJsonObject jsonObject;jsonObject.insert("Date", QDateTime::currentDateTime().toString());jsonObject.insert("Band", "20");QJsonObject jsonSenderLatObject;jsonSenderLatObject.insert("Lat", 13);jsonSenderLatObject.insert("Lon", 122);jsonSenderLatObject.insert("Sender", "DX0HQ");QJsonObject jsonReceiverLatObject;jsonReceiverLatObject.insert("Lat", 36.400001525878906);jsonReceiverLatObject.insert("Lon", 138.3800048828125);jsonReceiverLatObject.insert("Receiver", "8N3HQ");jsonObject.insert("Receiver", jsonReceiverLatObject);jsonObject.insert("Sender", jsonSenderLatObject);jsonArray.append(jsonObject);}QJsonObject finalObject;finalObject.insert("number", jsonArray.size());jsonArray.append(finalObject);QJsonDocument jsonDoc;jsonDoc.setArray(jsonArray);file.write(jsonDoc.toJson());file.close();qDebug() << "Write to file";
}

输出的JSON文件内容如下：

[{"Band": "20","Date": "Sat Jul 10 12:00:00 2021","Receiver": {"Lat": 36.400001525878906,"Lon": 138.3800048828125,"Receiver": "8N3HQ"},"Sender": {"Lat": 13,"Lon": 122,"Sender": "DX0HQ"}},// 其他条目省略{"number": 10}
]