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NullPointerException while dealing with creating an intent in MainActivity [duplicate]

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What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 5 years ago.
I've been looking into this for a few days and can't seem to find a thread specific to my problem. My app crashes every time I try to add a string to my bundle.
I'm getting the error at extras.putString(EXTRA_MESSAGE, message);
MainActivity.java
public class MainActivity extends AppCompatActivity {
private ArrayList<String> priceGroupSpinnerItems;
public static final String EXTRA_MESSAGE = "lss.mywebsiteoffline.MESSAGE";
public String message = "";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Spinner spnPriceGroup = (Spinner) findViewById(R.id.price_group_spinner);
ArrayAdapter adapter = ArrayAdapter.createFromResource(this, R.array.list_price_group, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spnPriceGroup.setAdapter(adapter);
message = spnPriceGroup.getSelectedItem().toString();
}
/** Called when the user taps the Go button */
public void sendMessage(View view) {
Intent mIntent;
mIntent = new Intent(this, nextActivity.class);
Bundle extras = mIntent.getExtras();
extras.putString(EXTRA_MESSAGE, message);
mIntent.putExtras(extras);
startActivity(mIntent);
}
}
Logcat
E/AndroidRuntime: FATAL EXCEPTION: main
Process: lss.mybbofflinever3, PID: 8181
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:5702)
at android.widget.TextView.performClick(TextView.java:10896)
at android.view.View$PerformClick.run(View.java:22546)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7224)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:5702) 
at android.widget.TextView.performClick(TextView.java:10896) 
at android.view.View$PerformClick.run(View.java:22546) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:158) 
at android.app.ActivityThread.main(ActivityThread.java:7224) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.os.Bundle.putString(java.lang.String, java.lang.String)' on a null object reference
at lss.mywebsiteoffline.MainActivity.sendMessage(MainActivity.java:59)
I have tried examples to use just intent, or bundle, and adding strings directly to putString. I might be missing something blatantly obvious. Not sure what I might be looking for after adding strings directly to the putString method and getting the same error.

By default an Intent does not have extras and getExtras() returns null. If you want to set extras, you need to create the extras bundle yourself. Replace
Bundle extras = mIntent.getExtras();
with
Bundle extras = new Bundle();
Or just call one of the putExtra() overloads on the Intent - it will also init the extras bundle in case it's not there already.

Try this:
Intent mIntent = new Intent(this, nextActivity.class);
mIntent.putExtra(EXTRA_MESSAGE, message);
startActivity(mIntent);

Start another activity in another class

I have a three class: MainActivity, BackgroundActivity and roomActivity.
BackgroundActivity will receipt the php server feedback.
If it is not login fail, it will call RoomActivity class.
I want to know that why is not functioning?
BackgroundActivity:
protected void onPostExecute(String result) {
if (result.equals("<meta charset=\"utf-8\">login fail")) {
alertDialog.setMessage("Please check your login email");
alertDialog.show();
} else {
**Intent myIntent = new Intent(MainActivity.class, RoomActivity.class);
startActivity(myIntent);**
}
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.a20_1discussboard, PID: 2262
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.content.ContextWrapper.getPackageName(ContextWrapper.java:132)
at android.content.ComponentName.<init>(ComponentName.java:77)
at android.content.Intent.<init>(Intent.java:4160)
at com.example.a20_1discussboard.MainActivity.check(MainActivity.java:38)
at com.example.a20_1discussboard.BackgroundWorker.onPostExecute(BackgroundWorker.java:151)
at com.example.a20_1discussboard.BackgroundWorker.onPostExecute(BackgroundWorker.java:24)
at android.os.AsyncTask.finish(AsyncTask.java:636)
at android.os.AsyncTask.access$500(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:653)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
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:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

change it to
Intent myIntent = new Intent(MainActivity.this, RoomActivity.class);

Calling startActivity() from outside of an Activity may produce AndroidRuntimeException, Use Context like:
Intent myIntent = new Intent(MainActivity.class, RoomActivity.class);
getApplicationContext().startActivity(myIntent);

Intent constructor is wrong.
it should be like :
Intent myIntent = new Intent(getApplicationContext(), RoomActivity.class);
startActivity(myIntent);
could you post more info about the issue ?

android.app.ActivityThread.getApplicationThread()' on a null object reference

The microhonePopUp method will work in MainActivity, but I'd like for it to work from another class (MediaButtonIntentReceiver). The problem is with startActivityForResult(intent, REQUEST_CODE); - but I don't know how to resolve it.
in the MainActivity class
public void microphonePopUp(){
Intent intent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL,
RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
intent.putExtra(RecognizerIntent.EXTRA_PROMPT, "Voice your answer");
startActivityForResult(intent, REQUEST_CODE);
}
in the MediaButtonIntentReceiver class
public class MediaButtonIntentReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
if (Intent.ACTION_MEDIA_BUTTON.equals(intent.getAction())) {
KeyEvent event = (KeyEvent)intent.getParcelableExtra(Intent.EXTRA_KEY_EVENT);
if (KeyEvent.KEYCODE_HEADSETHOOK == event.getKeyCode()) {
MainActivity test = new MainActivity();
test.microphonePopUp();
}
}
}
}
12-09 11:20:14.803 19556-19556/com.timtennyson.priceaddition
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.timtennyson.priceaddition, PID: 19556
java.lang.RuntimeException: Unable to start receiver
com.timtennyson.priceaddition.MediaButtonIntentReceiver:
java.lang.NullPointerException: Attempt to invoke virtual method
'android.app.ActivityThread$ApplicationThread
android.app.ActivityThread.getApplicationThread()' on a null object
reference
at android.app.ActivityThread.handleReceiver(ActivityThread.java:3641)
at android.app.ActivityThread.access$2000(ActivityThread.java:221)
at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1876)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7224)
at java.lang.reflect.Method.invoke(Native Method)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual
method 'android.app.ActivityThread$ApplicationThread
android.app.ActivityThread.getApplicationThread()' on a null object
reference
at android.app.Activity.startActivityForResult(Activity.java:4283)
at android.app.Activity.startActivityForResult(Activity.java:4230)
at
android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:842)
at
com.timtennyson.priceaddition.MainActivity.microphonePopUp(MainActivity.java:103)
at
com.timtennyson.priceaddition.MediaButtonIntentReceiver.onReceive(MediaButtonIntentReceiver.java:27)
at android.app.ActivityThread.handleReceiver(ActivityThread.java:3634)
at android.app.ActivityThread.access$2000(ActivityThread.java:221) 
at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1876) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:158) 
at android.app.ActivityThread.main(ActivityThread.java:7224) 
at java.lang.reflect.Method.invoke(Native Method)

NEVER create an instance of an activity, service, or provider yourself.
If your objective is to listen for ACTION_MEDIA_BUTTON broadcasts while MainActivity is visible:
Move MediaButtonIntentReceiver to be a nested class inside of MainActivity
Get rid of test from onReceive(), and just call microphonePopUp() (which I assume is a method on MainActivity)
Register your MediaButtonIntentReceiver using registerReceiver() in onStart() of MainActivity, and use unregisterReceiver() in onStop()
If your objective is to listen ACTION_MEDIA_BUTTON broadcasts at other points in time — by registering your receiver in the manifest — while you can do that, you cannot use microphonePopUp() from that receiver.

Getting arraylist from Service in BroadcastReceiver gives NullpointerException

I have a AsyncTask in a Service. I send an ArrayList as broadcast from the AsyncTask.
When I get the ArrayList in onReceive() I get a NullpointerException.
This is how I send the ArrayList.
transits_list = new ArrayList<Transit>();
transits_list.add(trs);
Intent arrayListIntent = new Intent("arrayList");
Bundle extra = new Bundle();
extra.putSerializable("transArray", transits_list);
intent.putExtra("extra", extra);
sendBroadcast(arrayListIntent);
The Transit class implements Serializable.
Receiving the ArrayList
#Override
public void onReceive(Context context, Intent intent) {
ArrayList<Transit> myList;
Bundle extra = getIntent().getBundleExtra("extra");
ArrayList<Transit> transArrayListFromBroadCast = (ArrayList<Transit>) extra.getSerializable("transArray");
System.out.print("transArrayListFromBroadCast "+transArrayListFromBroadCast);
}
I get NullpointerException in this line:
ArrayList<Transit> transArrayListFromBroadCast = (ArrayList<Transit>) extra.getSerializable("transArray");
The exception from log:
FATAL EXCEPTION: main
java.lang.RuntimeException: Error receiving broadcast Intent { act=arrayList flg=0x10 } in com.prematix.tollsystem.avcc.AvccActivity$ArrayListReceiver#42003268
at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:798)
at android.os.Handler.handleCallback(Handler.java:800)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5391)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.prematix.tollsystem.avcc.AvccActivity$ArrayListReceiver.onReceive(AvccActivity.java:271)
at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:788)
at android.os.Handler.handleCallback(Handler.java:800) 
at android.os.Handler.dispatchMessage(Handler.java:100) 
at android.os.Looper.loop(Looper.java:194) 
at android.app.ActivityThread.main(ActivityThread.java:5391) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:525)

Your method of getting the Intent is incorrect. I believe your BroadcastReceiver is in an activity class since, you are calling getIntent(). However, getIntent() will get you the Intent supplied to the activity and not the receiver. The Intent for receiver is provided to the method onReceive() itself. Make the following changes to your code:
Adding extra:
Intent arrayListIntent = new Intent("arrayList");
Bundle extra = new Bundle();
extra.putSerializable("transArray", transits_list);
intent.putExtra("extra", extra);
sendBroadcast(arrayListIntent);
Getting Extra:
#Override
public void onReceive(Context context, Intent intent) {
ArrayList<Transit> myList;
Bundle extra = intent.getBundleExtra("extra");
ArrayList<Transit> transArrayListFromBroadCast = (ArrayList<Transit>) extra.getSerializable("transArray");
// System.out.print("transArrayListFromBroadCast "+transArrayListFromBroadCast);
}

How to access a variable from another activity

So I'm trying to access a string from my main activity in my Locator activity, if I try to instantiate the String as public static it throws an error and says I cannot declare a static string in a non-static class, and when I tried to get it through intents I get an error that says.[EDIT] Now I've been able to access the intent without an error now I get a NullPointerException
No Activity found to handle Intent { (has extras) }
this is my main activity code:
options = (Spinner) findViewById(R.id.optionselect);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
R.array.options, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
options.setAdapter(adapter);
String XxXSelect =options.getSelectedItem().toString();
Intent i = new Intent(MainActivity.this,Locator.class);
i.putExtra("XxXchoice",XxXSelect);
startActivity(i);
my locator activity code:
Line -> 204 String XxXChoicei = getIntent().getStringExtra("XxXchoice");
full logcat
Caused by: java.lang.NullPointerException
at com.example.adrian.trucktracker.Locator.Updater(Locator.java:204)
at com.example.adrian.trucktracker.Locator.clickedUpdate(Locator.java:265)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at android.view.View$1.onClick(View.java:3860)
            at android.view.View.performClick(View.java:4480)
            at android.view.View$PerformClick.run(View.java:18686)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:157)
            at android.app.ActivityThread.main(ActivityThread.java:5872)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)

you need Static Variable to declare global variable in Application Class,
so Change your code to:
class GlobalClass extends Application {
public static String myVal;
}
then whereever you need to access this data, get Application object by:
GlobalClass global=(GlobalClass)context.getApplication();
global.myVal="anything";
and don't forget to add it to the AndroidManifest.xml file
<application
android:name="packagename.GlobalClass"
....
....
//other codes here
</application>

Try this
Intent i = new Intent(Youractivity.this, locator.class);
Bundle b = new Bundle();
b.putString("XxXchoice", XxXSelect);
i.putExtras(b);
startActivity(i);
and for more info go to #Intent

Change your code to get rid of the Bundle.
Intent i = new Intent(MainActivity.this, Locator.class);
i.putExtra("XxXchoice", XxXSelect);
startActivity(i);
Then in the Locator class do this...
String XxXChoicei = getIntent().getStringExtra("XxXchoice");
You were complicating things by adding an exta Bundle to the Intent which already has the ability to carry a Bundle of its own.

you can use M D answer if you want to use intent. if you want to access String from Main Activity.java you can do like this
in your **MainActivity**
//declare a method
public static String getString() {
String result;
// assign value to string here
result = "your assingment"
return result;
}
and in your another activity
//get value like this
String string = MainActivity.getString();
This way is used to access variable whenever required.