我正在尝试加载已下载并保存在iOS设备的persistentDataPath中的json文件。下载和保存效果很好。但是我认为加载文件有很大的问题。实际上，当我尝试在Xcode中编译项目时，会出现一些错误消息。
首先，这里是我的C＃代码：
using UnityEngine;
using System.Collections;
using System.IO;
using System.Net;
using UnityEngine.UI;
public class ReadJson : MonoBehaviour
{
public Text City;
public Text Temperature;
public Image Weather;
public Text WeatherUrl;
[System.Serializable]
public class CityInfo
{
public string name;
}
[System.Serializable]
public class CurrentCondition
{
public string date;
public string hour;
public int tmp;
public int wnd_spd;
public int wnd_gust;
public string wnd_dir;
public double pressure;
public int humidity;
public string condition;
public string icon;
public string icon_big;
}
[System.Serializable]
public class RootObject
{
public CityInfo city_info;
public CurrentCondition current_condition;
}
void Start () {
WebClient client = new WebClient();
File.Delete(Path.Combine (Application.persistentDataPath, "myjson.json"));
client.DownloadFile ("http://www.myjsonurl", Path.Combine (Application.persistentDataPath, "myjson.json"));
TextAsset asset = Resources.Load (Path.Combine (Application.dataPath + "/Documents", "myjson")) as TextAsset;
RootObject m = JsonUtility.FromJson<RootObject> (asset.text);
City.text = m.city_info.name;
Temperature.text = (m.current_condition.tmp).ToString();
}
}
现在是xcode控制台：
2016-10-21 17:01:20.766001 json[1404:516674] [DYMTLInitPlatform] platform initialization successful
2016-10-21 17:01:20.929950 json[1404:516508] -> registered mono modules 0xb95f70
2016-10-21 17:01:21.356590 json[1404:516508] You've implemented -[<UIApplicationDelegate> application:didReceiveRemoteNotification:fetchCompletionHandler:], but you still need to add "remote-notification" to the list of your supported UIBackgroundModes in your Info.plist.
-> applicationDidFinishLaunching()
2016-10-21 17:01:21.452967 json[1404:516508] Metal GPU Frame Capture Enabled
2016-10-21 17:01:21.453369 json[1404:516508] Metal API Validation Enabled
-> applicationDidBecomeActive()
Init: screen size 750x1334
Initializing Metal device caps
Initialize engine version: 5.3.4f1 (fdbb5133b820)
UnloadTime: 1.705875 ms
Salut/var/mobile/Containers/Data/Application/51A2490E-94EB-4904-9F2E-112AD5632A98/Documents
(Filename: /Users/builduser/buildslave/unity/build/artifacts/generated/common/runtime/UnityEngineDebugBindings.gen.cpp Line: 37)
NullReferenceException: A null value was found where an object instance was required.
(Filename: currently not available on il2cpp Line: -1)
Setting up 1 worker threads for Enlighten.
Thread -> id: 19f17000 -> priority: 1
如果有人有主意。在此先多谢。
您的代码存在以下问题：
TextAsset asset = Resources.Load(Path.Combine(Application.dataPath + "/Documents", "myjson")) as TextAsset;
我认为您不了解如何使用和何时使用Resources.Load。如果要使用该Resources.Load功能，则必须从编辑器中创建一个特殊文件夹。此文件夹应位于<ProjectDirectory>/Assets/Resources。您只能从编辑器将内容放入/写入该文件夹。在iOS上构建后，您将无法执行此操作。它只有在构建后才变为只读。然后可以使用该Resources.Load功能读取此特殊文件夹。
更换：
TextAsset asset = Resources.Load(Path.Combine(Application.dataPath + "/Documents", "myjson")) as TextAsset;
和
string text = File.ReadAllText(Path.Combine(Application.persistentDataPath, "myjson.json"));
RootObject m = JsonUtility.FromJson<RootObject>(text);
City.text = m.city_info.name;
Temperature.text = (m.current_condition.tmp).ToString();
应该解决你的问题。
另一个不应该使用的API是WebClient。除非您有充分的理由使用它，否则不应该这样做。您应该使用WWW或UnityWebRequest（较新的和推荐的）API。
这是没有WebClient以下代码的代码的外观：
void Start()
{
StartCoroutine(DownloadAndloadJson());
}
IEnumerator DownloadAndloadJson()
{
string url = "http://www.myjsonurl";
UnityWebRequest www = UnityWebRequest.Get(url);
yield return www.Send();
if (www.isError)
{
Debug.Log(www.error);
}
else
{
//Sucessfully downloaded the Json File
Debug.Log("Json: " + www.downloadHandler.text);
string jsonFile = www.downloadHandler.text;
//Delete old json file. Don't know why but this was in your original code
File.Delete(Path.Combine(Application.persistentDataPath, "myjson.json"));
//Save the downloaded data as File
File.WriteAllText(Path.Combine(Application.persistentDataPath, "myjson.json"), jsonFile);
//Load the downloaded data
string text = File.ReadAllText(Path.Combine(Application.persistentDataPath, "myjson.json"));
Debug.Log(text);
RootObject m = JsonUtility.FromJson<RootObject>(text);
City.text = m.city_info.name;
Temperature.text = (m.current_condition.tmp).ToString();
}
}
如果您有问题，请更新到Unity 5.4。该UnityWebRequestAPI应该用于此，它是在5.3推出，但错误是固定在5.4。您需要using UnityEngine.Networking;使用UnityWebRequest。
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我来说两句