我有一个扩展Fragment的类，但我也想在该片段中创建一个ListView。我按照[Androidhive JSON parse] [1]中关于如何解析JSON数据的教程。成功地尝试了一个项目，其唯一目的是从不同的链接做同样的事情。
然后我继续尝试使用来自[Androidhive Tab Layout] [2]的视图寻呼机实现标签。
在第二个项目中，我的一个选项卡意味着有一个列表视图，其中的数据是从链接中解析的。我创建了一个扩展AsyncTask的私有类，但是当我运行应用程序时， doInBackground（）方法导致应用程序崩溃...根据我的LogCat。
请帮忙，因为我不确定这个错误发生的确切位置，因为看起来我的try catch语句没有帮助，app在try catch块有机会显示哪些块导致错误之前崩溃。
我已经给了应用程序互联网许可。非常感谢帮助。
这是我的 doInBackground（）方法：
protected Void doInBackground(Void... params) {
ServiceHandler sh;
String jsonStr = "";
try {
// creating a service handler
sh = new ServiceHandler();
// making a request to url and getting response
// String jsonStr = sh.makeServiceCall(url,ServiceHandler.GET);
/*
* This code with concat json on it concatentates 7json arrays
* from whatsonwindhoek by simply having the first
* array,replacing the ] with a , and then appending other
* arrays for 5 other days. Loops by replacing the ] with a ,
* and finally when it exits the loop it adds the array from the
* last day after it replaces the first char which is a [ with a
* ,
*/
// trying json concatenation here
// array of first day of events i.e. current day
jsonStr = sh.makeServiceCall(url2 + "0", ServiceHandler.GET);
// variables to store and manipulate the arrays as they come
String appendedJSON;
StringBuffer buffer, buffer2;
buffer = new StringBuffer(jsonStr);
// loop for days in between
for (int i = 1; i < 6; i++) {
buffer.setCharAt(buffer.length() - 1, ','); // replace last
// character
// which
// is a ] with a
// ,
appendedJSON = sh.makeServiceCall(url2 + i,
ServiceHandler.GET); // call
// arrays
// of
// other
// days
// one
// by
// one
buffer2 = new StringBuffer(appendedJSON);// new buffer to
// store
// appendedJSON
// result for
// manipulation
buffer2.deleteCharAt(0);// remove the first character which
// is a
// [
buffer.append(buffer2); // add manipulated data to buffer
// belonging to the first array
}// end for
appendedJSON = sh.makeServiceCall(url2 + "6",ServiceHandler.GET);// call
// for
// last
// day
buffer2 = new StringBuffer(appendedJSON);// pull data for
// manipulation
buffer2.setCharAt(0, ','); // replace [ with ,
buffer.append(buffer2);// append to final buffer
jsonStr = buffer.toString(); // convert back to string and end
// the
// madness of json concatenation
// end trying json concat stunt
} catch (Exception ex) {
Log.e("doInBackGround", "JSON concat problem");
Toast.makeText(getActivity(), "Error doInBackground(): " + ex.toString(),
Toast.LENGTH_SHORT).show();
}
if (jsonStr != null) {
try {
// convert string from result to json array
events = new JSONArray(jsonStr);
// loop for all json objects in the array
for (int i = 0; i < events.length(); i++) {
JSONObject event = events.getJSONObject(i);
String title = event.getString(TAG_TITLE);
String location = event.getString(TAG_LOCATION);
String description = event.getString(TAG_DESCRIPTION);
String organizer = event.getString(TAG_ORGANIZER);
String file = event.getString(TAG_FILE);
String email = event.getString(TAG_EMAIL);
HashMap<String, String> singleEvent = new HashMap<String, String>();
singleEvent.put(TAG_TITLE, title);
singleEvent.put(TAG_EMAIL, email);
singleEvent.put(TAG_LOCATION, location);
eventList.add(singleEvent);
}// endfor
} catch (JSONException e) {
Log.e("doInBackGround", "JSON problem");
Toast.makeText(getActivity(), "Error doInBackground(): " + e.toString(),
Toast.LENGTH_SHORT).show();
}// endtrycatch
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}// endif
return null;
}
以及仅来自我的LogCat的错误记录：
<i>06-30 00:42:08.093: E/(28963): Warning: Could not set thread affinity 1. continueing..
06-30 00:44:14.538: E/(29611): Warning: Could not set thread affinity 1. continueing..
06-30 00:44:42.208: E/(29862): Warning: Could not set thread affinity 1. continueing..
06-30 00:46:08.898: E/AndroidRuntime(29862): FATAL EXCEPTION: AsyncTask #1
06-30 00:46:08.898: E/AndroidRuntime(29862): java.lang.RuntimeException: An error occured while executing doInBackground()
06-30 00:46:08.898: E/AndroidRuntime(29862): at android.os.AsyncTask$3.done(AsyncTask.java:278)
06-30 00:46:08.898: E/AndroidRuntime(29862): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
06-30 00:46:08.898: E/AndroidRuntime(29862): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
06-30 00:46:08.898: E/AndroidRuntime(29862): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
06-30 00:46:08.898: E/AndroidRuntime(29862): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
06-30 00:46:08.898: E/AndroidRuntime(29862): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
06-30 00:46:08.898: E/AndroidRuntime(29862): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
06-30 00:46:08.898: E/AndroidRuntime(29862): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
06-30 00:46:08.898: E/AndroidRuntime(29862): at java.lang.Thread.run(Thread.java:856)
06-30 00:46:08.898: E/AndroidRuntime(29862): Caused by: java.lang.NullPointerException
06-30 00:46:08.898: E/AndroidRuntime(29862): at com.inc.automata.whatsonwindhoek.main.WoWEvents$GetContacts.doInBackground(WoWEvents.java:194)
06-30 00:46:08.898: E/AndroidRuntime(29862): at com.inc.automata.whatsonwindhoek.main.WoWEvents$GetContacts.doInBackground(WoWEvents.java:1)
06-30 00:46:08.898: E/AndroidRuntime(29862): at android.os.AsyncTask$2.call(AsyncTask.java:264)
06-30 00:46:08.898: E/AndroidRuntime(29862): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
06-30 00:46:08.898: E/AndroidRuntime(29862): ... 5 more
06-30 00:46:34.178: E/WindowManager(29862): Activity com.inc.automata.whatsonwindhoek.main.MainActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@419086d8 that was originally added here
06-30 00:46:34.178: E/WindowManager(29862): android.view.WindowLeaked: Activity com.inc.automata.whatsonwindhoek.main.MainActivity has
06-30 00:46:34.178: E/WindowManager(29862): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1478)
06-30 00:46:34.178: E/WindowManager(29862): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
06-30 00:46:34.178: E/WindowManager(29862): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
06-30 00:46:34.178: E/WindowManager(29862): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
06-30 00:46:34.178: E/WindowManager(29862): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1460)
06-30 00:46:34.178: E/WindowManager(29862): at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
06-30 00:46:34.178: E/WindowManager(29862): at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
06-30 00:46:34.178: E/WindowManager(29862): at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
06-30 00:46:34.178: E/WindowManager(29862): at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
06-30 00:46:34.178: E/WindowManager(29862): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
06-30 00:46:34.178: E/WindowManager(29862): at android.view.View.measure(View.java:12899)
06-30 00:46:34.178: E/WindowManager(29862): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
06-30 00:46:34.178: E/WindowManager(29862): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-30 00:46:34.178: E/WindowManager(29862): at android.view.View.measure(View.java:12899)
06-30 00:46:34.178: E/WindowManager(29862): at android.widget.LinearLayout.measureVertical(LinearLayout.java:812)
06-30 00:46:34.178: E/WindowManager(29862): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
06-30 00:46:34.178: E/WindowManager(29862): at android.view.View.measure(View.java:12899)
06-30 00:46:34.178: E/WindowManager(29862): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
06-30 00:46:34.178: E/WindowManager(29862): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-30 00:46:34.178: E/WindowManager(29862): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2249)
06-30 00:46:34.178: E/WindowManager(29862): at android.view.View.measure(View.java:12899)
06-30 00:46:34.178: E/WindowManager(29862): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1179)
06-30 00:46:34.178: E/WindowManager(29862): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2565)
06-30 00:46:34.178: E/WindowManager(29862): at android.os.Handler.dispatchMessage(Handler.java:99)
06-30 00:46:34.178: E/WindowManager(29862): at android.os.Looper.loop(Looper.java:137)
06-30 00:46:34.178: E/WindowManager(29862): at android.app.ActivityThread.main(ActivityThread.java:4502)
06-30 00:46:34.178: E/WindowManager(29862): at java.lang.reflect.Method.invokeNative(Native Method)
06-30 00:46:34.178: E/WindowManager(29862): at java.lang.reflect.Method.invoke(Method.java:511)
06-30 00:46:34.178: E/WindowManager(29862): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:805)
06-30 00:46:34.178: E/WindowManager(29862): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:572)
06-30 00:46:34.178: E/WindowManager(29862): at dalvik.system.NativeStart.main(Native Method)
</i>
[1]: http://www.androidhive.info/2012/01/android-json-parsing-tutorial/
[2]: http://www.androidhive.info/2013/10/android-tab-layout-with-swipeable-views-1/