[英]QJsonObject returns null
QJsonObject 不會正常返回值。
json
{"response":{"header":{"resultCode":"0000","resultMsg":"OK"},"body":{"items":{"item":[{"baseDate":20190413,"baseTime":"0600","category":"PTY","nx":55,"ny":127,"obsrValue":0},{"baseDate":20190413,"baseTime":"0600","category":"REH","nx":55,"ny":127,"obsrValue":-998},{"baseDate":20190413,"baseTime":"0600","category":"RN1","nx":55,"ny":127,"obsrValue":0},{"baseDate":20190413,"baseTime":"0600","category":"T1H","nx":55,"ny":127,"obsrValue":6.3},{"baseDate":20190413,"baseTime":"0600","category":"UUU","nx":55,"ny":127,"obsrValue":0},{"baseDate":20190413,"baseTime":"0600","category":"VEC","nx":55,"ny":127,"obsrValue":0},{"baseDate":20190413,"baseTime":"0600","category":"VVV","nx":55,"ny":127,"obsrValue":0},{"baseDate":20190413,"baseTime":"0600","category":"WSD","nx":55,"ny":127,"obsrValue":0}]},"numOfRows":10,"pageNo":1,"totalCount":8}}}
代碼
QJsonDocument jsonDoc = QJsonDocument::fromJson(reply->readAll());
QJsonObject jsonObj = jsonDoc.object();
QString status = jsonObj["resultMsg"].toString(); // empty
QJsonArray items = jsonObj["item"].toArray(); // null
我希望 OK 存儲在狀態變量中,但它不包含任何內容。
items 變量存儲空值。
要理解最好使用以下格式查看 json:
{
"response": {
"header": {
"resultCode": "0000",
"resultMsg": "OK"
},
"body": {
"items": {
"item": [{
"baseDate": 20190413,
"baseTime": "0600",
"category": "PTY",
"nx": 55,
"ny": 127,
"obsrValue": 0
}, {
"baseDate": 20190413,
"baseTime": "0600",
"category": "REH",
"nx": 55,
"ny": 127,
"obsrValue": -998
}, {
"baseDate": 20190413,
"baseTime": "0600",
"category": "RN1",
"nx": 55,
"ny": 127,
"obsrValue": 0
}, {
"baseDate": 20190413,
"baseTime": "0600",
"category": "T1H",
"nx": 55,
"ny": 127,
"obsrValue": 6.3
}, {
"baseDate": 20190413,
"baseTime": "0600",
"category": "UUU",
"nx": 55,
"ny": 127,
"obsrValue": 0
}, {
"baseDate": 20190413,
"baseTime": "0600",
"category": "VEC",
"nx": 55,
"ny": 127,
"obsrValue": 0
}, {
"baseDate": 20190413,
"baseTime": "0600",
"category": "VVV",
"nx": 55,
"ny": 127,
"obsrValue": 0
}, {
"baseDate": 20190413,
"baseTime": "0600",
"category": "WSD",
"nx": 55,
"ny": 127,
"obsrValue": 0
}]
},
"numOfRows": 10,
"pageNo": 1,
"totalCount": 8
}
}
}
Json 是一種格式,其中每個元素都有一個層次結構,也就是說,要訪問一個元素,您必須通過其父元素來完成。
在 resultMsg 的情況下,您必須訪問response -> header-> resultMsg
。 在 item 的情況下,您必須訪問response -> body-> items-> item
。
綜上所述,解決方法是:
QJsonArray item_array;
QString status;
QJsonDocument jsonDoc = QJsonDocument::fromJson(reply->readAll());
QJsonObject jsonObj = jsonDoc.object();
if(jsonObj.contains("response")){
QJsonObject response_obj = jsonObj["response"].toObject();
if(response_obj.contains("header")){
QJsonObject header_obj = response_obj["header"].toObject();
if(header_obj.contains("resultMsg")){
status = header_obj["resultMsg"].toString();
}
}
if(response_obj.contains("body")){
QJsonObject body_obj = response_obj["body"].toObject();
if(body_obj.contains("items")){
QJsonObject items_obj = body_obj["items"].toObject();
if(items_obj.contains("item")){
item_array = items_obj["item"].toArray();
}
}
}
}
qDebug()<< "status:" << status;
qDebug()<< "item:" << item_array;
輸出:
status: "OK"
item: QJsonArray([{"baseDate":20190413,"baseTime":"0600","category":"PTY","nx":55,"ny":127,"obsrValue":0},{"baseDate":20190413,"baseTime":"0600","category":"REH","nx":55,"ny":127,"obsrValue":-998},{"baseDate":20190413,"baseTime":"0600","category":"RN1","nx":55,"ny":127,"obsrValue":0},{"baseDate":20190413,"baseTime":"0600","category":"T1H","nx":55,"ny":127,"obsrValue":6.3},{"baseDate":20190413,"baseTime":"0600","category":"UUU","nx":55,"ny":127,"obsrValue":0},{"baseDate":20190413,"baseTime":"0600","category":"VEC","nx":55,"ny":127,"obsrValue":0},{"baseDate":20190413,"baseTime":"0600","category":"VVV","nx":55,"ny":127,"obsrValue":0},{"baseDate":20190413,"baseTime":"0600","category":"WSD","nx":55,"ny":127,"obsrValue":0}])
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