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How to fix java.lang.IllegalStateException

I'm currently working on my A Level Computer Science controlled assessment, making a Scout Manager App in Android Studio, using Java and XML - none of which I have used before. I'm now working on a n event creator.
I'm trying to create a record, which will show which transport has been selected for which event, however I have run into a problem - the LogCat is giving me the following error:
04-02 15:25:42.663 18482-18482/com.example.atomi.scoutmanagerprototype E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.atomi.scoutmanagerprototype, PID: 18482
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:390)
at android.view.View.performClick(View.java:4761)
at android.view.View$PerformClick.run(View.java:19767)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5310)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
at android.view.View.performClick(View.java:4761)
at android.view.View$PerformClick.run(View.java:19767)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5310)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/data/com.example.atomi.scoutmanagerprototype/databases/ScoutManager.db
at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:55)
at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1158)
at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1034)
at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1202)
at com.example.samogonovsky.scoutmanager.databaseHandler.getRandomTransport(databaseHandler.java:649)
at com.example.samogonovsky.scoutmanager.frmCreateEvent2.saveAndExit(frmCreateEvent2.java:528)
However, I have not closed the cursor in either of these two places.
Here is the code in the "databaseHandler" class:
//Select a random mode of transport
public Cursor getRandomTransport()
{
Cursor cursor=db.query(TABLE_TRANSPORT, null, null, null, null, null, "RANDOM()limit 1");
if (cursor!=null&&cursor.moveToFirst())
{
cursor.moveToFirst();
}
else
{
cursor=null;
}
return cursor;
}
And here is the code in the "frmAddEvent2" class:
double TotalTransportCost;
if (providingtransport==true)
{
int peopletotransport=noOfPeople;
TotalTransportCost = 0;
do
{
int eventtransportid=createEventTransportId();
Cursor ModeOfTransport = DatabaseHandler.getRandomTransport();
if (ModeOfTransport.moveToFirst()) {
int transportid=ModeOfTransport.getInt(ModeOfTransport.getColumnIndex(
DatabaseHandler.COLUMN_TRID));
double PriceForHiring = ModeOfTransport.getDouble(ModeOfTransport.getColumnIndex(
DatabaseHandler.COLUMN_HCOST));
double PricePerMile = ModeOfTransport.getDouble(ModeOfTransport.getColumnIndex(
DatabaseHandler.COLUMN_MCOST));
int NoOfSeats = ModeOfTransport.getInt(ModeOfTransport.getColumnIndex(
DatabaseHandler.COLUMN_SEATNO));
double ModeCost = ((PricePerMile*distancefrombase)+PriceForHiring);
eventTransportDetails eventtransport = new eventTransportDetails(eventtransportid,
id, transportid);
DatabaseHandler.createEventTransport(eventtransport);
BigDecimal bigdecimalmodecost=new BigDecimal(ModeCost);
BigDecimal bigdecimalpropermodecost=((bigdecimalmodecost.setScale(2,bigdecimalmodecost.ROUND_DOWN)));
double propermodecost=bigdecimalpropermodecost.doubleValue();
TotalTransportCost = TotalTransportCost + propermodecost;
peopletotransport = (peopletotransport-NoOfSeats);
ModeOfTransport.close();
}
else
{
Toast.makeText(
context,
"Error - you have not added any lunches, therefore food " +
"cannot be added.",
Toast.LENGTH_SHORT
).show();
return;
}
}
while (peopletotransport>0);
}
else
{
TotalTransportCost=0;
}
I was wondering if anybody could point me in the right direction?
Also, feel free to suggest any improvements to my question - as stated, a lot of this is new to me, so I may have left out some pretty important material.

Ok, so as it turns out, I put "db.close();" after a few of the functions in databaseHandler - by removing all of these, I fixed the problem. If you think this question would be better off not on the site, let me know and I'll delete it. Thanks though to all who commented.

java.lang.RuntimeException: Unable to resume activity with java.lang.IllegalArgumentException

Recently I sometimes got this exception when MainActivity called onResume().
java.lang.RuntimeException: Unable to resume activity {com.qau4d.c35s3.androidapp/com.xxx.XXX.XXX.MainActivity}: java.lang.IllegalArgumentException
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3400)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3440)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1510)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.IllegalArgumentException
at android.os.Parcel.readException(Parcel.java:1687)
at android.os.Parcel.readException(Parcel.java:1636)
at android.app.ActivityManagerProxy.isTopOfTask(ActivityManagerNative.java:5475)
at android.app.Activity.isTopOfTask(Activity.java:5961)
at android.app.Activity.onResume(Activity.java:1252)
at com.qau4d.c35s3.androidapp.onResume(XActivity.java:29)
at com.qau4d.c35s3.androidapp.onResume(MainActivity.java:196)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1269)
at android.app.Activity.performResume(Activity.java:6768)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3377)
Both in MainActivity and super class XActivity, only super.onResume(); is called. It's really strange to get this exception after a long time normal development.I checked some relative reference material but nothing got.

In the method Activity#isTopOfTask we can see:
private boolean isTopOfTask() {
if (mToken == null || mWindow == null) {
return false;
}
try {
return ActivityManager.getService().isTopOfTask(getActivityToken());
} catch (RemoteException e) {
return false;
}
}
And in ActivityManagerService#isTopOfTask we can found:
#Override
public boolean isTopOfTask(IBinder token) {
synchronized (this) {
ActivityRecord r = ActivityRecord.isInStackLocked(token);
if (r == null) {
throw new IllegalArgumentException();
}
return r.task.getTopActivity() == r;
}
}
So, I think that ActivityRecord is null.But I don't know why it is null....

There is insufficient information in your question to determine the cause of the java.lang.IllegalArgumentException, Unfortunately the android ActivityThread doesn't log the stacktrace of that exception, and the exception message appears to be empty.
However, it looks like there is a way forward. The exception is handled by the following code in the ActivityThread::performResumeActivity method:
} catch (Exception e) {
if (!mInstrumentation.onException(r.activity, e)) {
throw new RuntimeException(
"Unable to resume activity "
+ r.intent.getComponent().toShortString()
+ ": " + e.toString(), e);
}
}
If you register an Instrumentation class for your activity, it should be possible to use an onException method to log the stacktrace for the causal exception. Another possibility is to use Thread.setUncaughtExceptionHandler to set a handler for the thread in which the IllegalArgumentException is thrown.
These won't solve the problem (!) but it will get you a step closer to a solution.

Checking for internet connectivity in Android app [duplicate]

This question already has answers here:
How can I fix 'android.os.NetworkOnMainThreadException'?
(66 answers)
Closed 7 years ago.
I'm trying to check for INTERNET connectivity from an Android app but just keep running in to problems.
I'm NOT looking for code that tests for an available network connection - I've got that bit working - this is to test whether I can reach an internet site or not.
(I appreciate that if I am behind a system which presents a logon screen instead of the requested site, I may not get the exact result I want, but I will handle that later)
Thanks to the following question I think I've made some progress, but when I run the app it crashes out (error info below).
The code I have so far is as follows (and I must admit that I find the try/catch stuff a bit puzzling and tedious :-/ )
static public boolean isInternetReachable() {
int statusCode = -1;
try{
URL url = new URL("http://www.google.com/humans.txt");
HttpURLConnection http = (HttpURLConnection) url.openConnection();
statusCode = http.getResponseCode();
http.disconnect();
} catch (MalformedURLException ex) {
return false;
} catch (IOException ex) {
return false;
}
if (statusCode == HttpURLConnection.HTTP_OK) {
return true;
}
else
{
//connection is not OK
return false;
}
}
I'm sure there are neater ways to do this and so any general advice is welcome.
The error that I'm getting when the app crashes is:
01-24 19:53:14.767 10617-10617/com.nooriginalthought.bluebadgeparking E/AndroidRuntime:
FATAL EXCEPTION: main
Process: com.nooriginalthought.bluebadgeparking, PID: 10617
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.nooriginalthought.bluebadgeparking/com.nooriginalthought.bluebadgeparking.PreLoadChecks}: android.os.NetworkOnMainThreadException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2411)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2474)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1359)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:155)
at android.app.ActivityThread.main(ActivityThread.java:5696)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1028)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)
Caused by: android.os.NetworkOnMainThreadException
at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1155)
at java.net.InetAddress.lookupHostByName(InetAddress.java:418)
at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252)
at java.net.InetAddress.getAllByName(InetAddress.java:215)
at com.android.okhttp.HostResolver$1.getAllByName(HostResolver.java:29)
at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:236)
at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:124)
at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:272)
at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:211)
at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:373)
at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:323)
at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponseCode(HttpURLConnectionImpl.java:491)
at com.nooriginalthought.bluebadgeparking.PreLoadChecks.isInternetReachable(PreLoadChecks.java:41)
at com.nooriginalthought.bluebadgeparking.PreLoadChecks.onCreate(PreLoadChecks.java:70)
at android.app.Activity.performCreate(Activity.java:5958)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1129)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2474) 
at android.app.ActivityThread.access$800(ActivityThread.java:144) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1359) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:155) 
at android.app.ActivityThread.main(ActivityThread.java:5696) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1028) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823) 

As David is mentioning in the comments, you should just Google for the Exception name and try to get a turnaround by yourself.
By looking at the StackOverflow answer that he is referring to, you need to make all network communications outside the Main thread. The most used way to do this is by creating an AsyncTask.
In your case, it would look (you can create a new InternetTask.java or just append it to your current MainActivity.java) something like:
class InternetTask extends AsyncTask<Void, Void, Boolean>{
private MainActivity activity;
InternetTask(MainActivity activity){
this.activity = activity;
}
#Override
protected Boolean doInBackground(Void... params) {
int statusCode = -1;
try{
URL url = new URL("http://www.google.com/humans.txt");
HttpURLConnection http = (HttpURLConnection) url.openConnection();
statusCode = http.getResponseCode();
http.disconnect();
} catch (MalformedURLException ex) {
return false;
} catch (IOException ex) {
return false;
}
if (statusCode == HttpURLConnection.HTTP_OK) {
return true;
}
else
{
//connection is not OK
return false;
}
}
#Override
protected void onPostExecute(Boolean aBoolean) {
super.onPostExecute(aBoolean);
activity.receiveMagic(aBoolean);
}
}
Then, you just need to add a new public method in your activity to receive the boolean in your MainActivity.
public void receiveMagic(Boolean isGood){
if (isGood){
Toast.makeText(MainActivity.this, "It is good", Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(MainActivity.this, "It is not connected", Toast.LENGTH_SHORT).show();
}
}
And you would need to call your new AsyncTask from your Activity with:
new InternetTask(this).execute();
Make sure you add the internet permission to your Manifest also.

Android ScheduledThreadPoolExecutor cause: null

I'm tearing my hair out with this one! I'm a newbie to Android so I'm sure it's something super obvious.
I'm getting a ScheduledThreadPoolExecutor exception where cause: null
All I want is a seperate thread that runs whenever the activity is on screen!
// Instance Variables
private ScheduledExecutorService m_oScheduledExecutor = null;
#Override
protected void onResume()
{
super.onResume();
if (oScheduledExecutor == null)
{
oScheduledExecutor = Executors.newSingleThreadScheduledExecutor();
}
try
{
oScheduledExecutor.scheduleAtFixedRate({Runnable Instance HERE}, 0, 10, TimeUnit.SECONDS);
}
catch (Exception e)
{
System.out.println("(MainActivity) Error: " + e.getMessage() + " Cause: " + e.getCause());
}
}
#Override
protected void onStop()
{
super.onStop();
m_oScheduledExecutor.shutdown();
}
EDIT: Entire Stack Trace....
java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask#41976688 rejected from java.util.concurrent.ScheduledThreadPoolExecutor#4195c7f8[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 1]
at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:1979)
at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:786)
at java.util.concurrent.ScheduledThreadPoolExecutor.delayedExecute(ScheduledThreadPoolExecutor.java:300)
at java.util.concurrent.ScheduledThreadPoolExecutor.scheduleAtFixedRate(ScheduledThreadPoolExecutor.java:545)
at java.util.concurrent.Executors$DelegatedScheduledExecutorService.scheduleAtFixedRate(Executors.java:619)
at com.example.wifitest.MainActivity.onResume(MainActivity.java:61)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1185)
at android.app.Activity.performResume(Activity.java:5182)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2732)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2771)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1276)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
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:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)

You cannot 'recycle' an ExecutorService. Once you have invoked shutdown(), attempting to schedule any task will cause a rejection, and in your case the rejection policy is to throw RejectedExecutionException.
If you follow your stacktrace, you can see in ScheduledThreadPoolExecutor:
/**
* Specialized variant of ThreadPoolExecutor.execute for delayed tasks.
*/
private void delayedExecute(Runnable command) {
if (isShutdown()) {
reject(command);
return;
}
// ...
}
Keeping your executor service as an instance variable is not going to work for you here: once it's been shutdown, it can't be used again.

Do not shutdown the ScheduledExecutorService inside onStop() method. Try to put it inside onDestroy() method. When your activity goes in background, onStop() method might be getting called, as your activity is not visible in the background. Because of this, if the ScheduledExecutorService is shutdown, you might be getting this error.

Geocoder.isPresent() causes NullPointerException?

I got the following error message from Google Play Developer Console.
Besides the try/catch I cannot find anything that could give a null pointer, was it the
Geocoder.isPresent() which is not available in API 8?
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.xxxxxxxx.SearchActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2100)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125)
at android.app.ActivityThread.access$600(ActivityThread.java:140)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4898)
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:1006)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.xxxxxxxx.SearchActivity.updateUserLocationNameBasedOnNewCoordinates(SearchActivity.java:367)
at com.xxxxxxxx.SearchActivity.useDeviceLocation(SearchActivity.java:338)
at com.xxxxxxxx.SearchActivity.start(SearchActivity.java:495)
at com.xxxxxxxx.SearchActivity.onCreate(SearchActivity.java:253)
at android.app.Activity.performCreate(Activity.java:5206)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1083)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2064)
... 11 more
ACTIVITY:
public void updateUserLocationNameBasedOnNewCoordinates() {
String city = null;
String country = null;
Geocoder geocoder = new Geocoder(this, Locale.getDefault());
List<Address> list;
if (Geocoder.isPresent()) {
try {
list = geocoder.getFromLocation(userLocation.getLatitude(),
userLocation.getLongitude(), 1);
Address address = list.get(0);
city = address.getLocality();
country = address.getCountryName();
} catch (IOException e) {
e.printStackTrace();
}
}
if (city == null || country == null)
locationDescription = "Map location";
else
locationDescription = city + " " + country;
}
MANIFEST:
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />

If you see the documentation of Geocoder.isPresent(), it says: Lack of network connectivity may still cause these methods to return null or empty lists. So make sure you are connected.
Other important thing is that the document says that it was added in API level 9 but you have stated android:minSdkVersion=8 in the manifest. Try to mention android:minSdkVersion=9 or above. Hope this helps.