在没有Internet连接的情况下加载本地JsonData
我正在制作一个Android应用程序，我想在其中加载json数据。我的规格是，如果有可用的互联网，那么从我提供的网址加载数据。
如果没有互联网，请加载本地json.txt文件。
如果有互联网连接，我的应用程序可以从网址加载数据，如果绝对没有互联网连接，它可以加载本地json数据。
但是在这样的元状态下，我的应用程序崩溃了。
日志
07-14 09:56:21.258 22499-28349/scientist.jobless.foodmana E/log_tag﹕ Error in http connection java.net.UnknownHostException: Unable to resolve host "lit-hamlet-6856.herokuapp.com": No address associated with hostname
07-14 09:56:21.258 22499-28349/scientist.jobless.foodmana E/log_tag﹕ Error converting result java.lang.NullPointerException
07-14 09:56:21.258 22499-28349/scientist.jobless.foodmana E/log_tag﹕ Error parsing data org.json.JSONException: End of input at character 0 of
07-14 09:56:21.266 22499-28349/scientist.jobless.foodmana E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:299)
at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
at java.util.concurrent.FutureTask.run(FutureTask.java:137)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
at java.lang.Thread.run(Thread.java:856)
Caused by: java.lang.NullPointerException
at scientist.jobless.foodmana.JsonLoadSubFirstFirst$DownloadJSON.doInBackground(JsonLoadSubFirstFirst.java:239)
at scientist.jobless.foodmana.JsonLoadSubFirstFirst$DownloadJSON.doInBackground(JsonLoadSubFirstFirst.java:215)
at android.os.AsyncTask$2.call(AsyncTask.java:287)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
at java.util.concurrent.FutureTask.run(FutureTask.java:137)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
at java.lang.Thread.run(Thread.java:856)
07-14 09:56:21.878 22499-22499/scientist.jobless.foodmana E/WindowManager﹕ Activity scientist.jobless.foodmana.JsonLoadSubFirstFirst has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@5374c12c that was originally added here
android.view.WindowLeaked: Activity scientist.jobless.foodmana.JsonLoadSubFirstFirst has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@5374c12c that was originally added here
at android.view.ViewRootImpl.<init>(ViewRootImpl.java:374)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:292)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:224)
at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:149)
at android.view.Window$LocalWindowManager.addView(Window.java:547)
at android.app.Dialog.show(Dialog.java:277)
at scientist.jobless.foodmana.MyCustomProgressDialog.show(MyCustomProgressDialog.java:43)
at scientist.jobless.foodmana.JsonLoadSubFirstFirst$DownloadJSON.onPreExecute(JsonLoadSubFirstFirst.java:227)
at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
at android.os.AsyncTask.execute(AsyncTask.java:534)
at scientist.jobless.foodmana.JsonLoadSubFirstFirst.onCreate(JsonLoadSubFirstFirst.java:74)
at android.app.Activity.performCreate(Activity.java:5008)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
at android.app.ActivityThread.access$600(ActivityThread.java:130)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
下面是我的java代码，我正在检查连接类型。
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Get the view from listview_main.xml
setContentView(R.layout.listview_main);
// Execute DownloadJSON AsyncTask
ConnectivityManager connec = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
if (connec != null && (
(connec.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.CONNECTED) ||
(connec.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.CONNECTED))) {
new DownloadJSON(this).execute();
//You are connected, do something online.
} else if (connec != null && (
(connec.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.DISCONNECTED) ||
(connec.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.DISCONNECTED ))) {
//Not connected.
Toast.makeText(getApplicationContext(), "You must be connected to the internet", Toast.LENGTH_LONG).show();
new LocalDownloadJSON().execute();
}
else if (connec != null && (
(connec.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.UNKNOWN) ||
(connec.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.UNKNOWN ))) {
//i want to load local json data here
}
}
我的问题是如何处理我在模拟器图片中显示的元连接状态。
我已经尝试了this 回答，但我在isNetworkAvailable(context)上收到错误，因为无法解析方法isNetworkAvailable。
这个代码还有吗？
(connec != null && (
(connec.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.UNKNOWN) ||
(connec.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.UNKNOWN )))
LocalJsonDownload.java
private class LocalDownloadJSON extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog(JsonLoadSubFirstFirst.this);
pd.setMessage("Loading...");
pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);
pd.setIndeterminate(true);
pd.setCancelable(false);
pd.show();
}
@Override
protected Void doInBackground(Void... params) {
// Create an array
localarraylist = new ArrayList<HashMap<String, String>>();
// Retrieve JSON Objects from the given URL address
StringBuffer sb = new StringBuffer();
BufferedReader br = null;
try {
br = new BufferedReader(new InputStreamReader(getAssets().open("localfood.txt")));
String temp;
while ((temp = br.readLine()) != null)
sb.append(temp);
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
try
{
br.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
myjsonstring = sb.toString();
try{
JSONObject jsonObj = new JSONObject(myjsonstring);
JSONArray Attendance = jsonObj.getJSONArray("events");
for (int i = 0; i < Attendance.length(); i++)
{
JSONObject a = Attendance.getJSONObject(i);
String Name = a.getString("Name");
String time = a.getString("Time");
String ingredients = a.getString("ingredients");
String Serves = a.getString("Serves");
String descr = a.getString("Description");
HashMap<String, String> contact = new HashMap<String, String>();
// adding each child node to HashMap key => value
contact.put("Name", Name);
contact.put("Time", time);
contact.put("ingredients", ingredients);
contact.put("Serves", Serves);
contact.put("Description", descr);
// adding contact to contact list
localarraylist.add(contact);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void args) {
Toast.makeText(getApplicationContext(),"Loading local data dishes, please connect o internet to load new dishes",Toast.LENGTH_LONG).show();
// Locate the listview in listview_main.xml
//setContentView(R.layout.listview_main);
listview = (ListView) findViewById(R.id.listview);
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(JsonLoadSubFirstFirst.this, localarraylist);
// Set the adapter to the ListView
listview.setAdapter(adapter);
// Close the progressdialog
// mProgressDialog.dismiss();
// textView.setVisibility(View.VISIBLE);
pd.dismiss();
super.onPostExecute(args);
}
}
3 个答案:
答案 0 :(得分：1)
当互联网可用时，您可以在加载json数据时执行一项操作，您可以将其保存到sqite中，并在下次加载时检查网络是否可用，如果网络不可用，则可以从sqlite获取json数据并解析很简单。你可以使用GreenDao来实现它非常快速和可靠的
答案 1 :(得分：0)
由于互联网连接，似乎没有正确下载json文件。因此，当您读取不完整的下载文件时，它会抛出“JSONException：输入结束于字符0”
在阅读下载的文件之前，您应该检查原始文件大小的下载文件大小。可以在HTTP标头中找到原始文件大小。
或者您在服务器上有无效的json文件。
希望你会发现它有用。
答案 2 :(得分：0)
您无法处理此连接状态。唯一的方法是捕获IOException。更好的方法是在DownloadJSON的doInBackground方法中捕获IOException和JSONException，然后执行LocalDownloadJSON
// POST: RecurringTemplate/Create
[HttpPost]
public ActionResult Create(RecurringTemplate recurringTemplate)
{
try
{
_repo.AddRecurringTemplate(recurringTemplate);
return RedirectToAction("Index");
}
catch
{
return View();
}
}
编辑： 更好地解析onPostExecute中的Json
@Html.LabelFor(model => model.Schedule.Build_Time)
<span class="glyphicon glyphicon-time"></span>
@Html.EditorFor(model => model.Schedule.Build_Time, new {htmlAttributes = new {@class = "form-control"}})
@Html.LabelFor(model => model.Schedule.Call_Start_Time)
<span class="glyphicon glyphicon-time"></span>
@Html.EditorFor(model => model.Schedule.Call_Start_Time, new {htmlAttributes = new {@class = "form-control"}})
@Html.ValidationMessageFor(model => model.Schedule.Call_Start_Time, "", new {@class = "text-danger"})
@Html.LabelFor(model => model.Schedule.Call_End_Time)
<span class="glyphicon glyphicon-time"></span>
@Html.EditorFor(model => model.Schedule.Call_End_Time, new {htmlAttributes = new {@class = "form-control"}})
相关问题
最新问题
- 我写了这段代码，但我无法理解我的错误
- 我无法从一个代码实例的列表中删除 None 值，但我可以在另一个实例中。为什么它适用于一个细分市场而不适用于另一个细分市场？
- 是否有可能使 loadstring 不可能等于打印？卢阿
- java中的random.expovariate()
- Appscript 通过会议在 Google 日历中发送电子邮件和创建活动
- 为什么我的 Onclick 箭头功能在 React 中不起作用？
- 在此代码中是否有使用“this”的替代方法？
- 在 SQL Server 和 PostgreSQL 上查询，我如何从第一个表获得第二个表的可视化
- 每千个数字得到
- 更新了城市边界 KML 文件的来源？