How can I initialize an interface in the MainActivity?
I have tried it like the following, but it keeps giving error.
MainActivity:
public class MainActivity extends AppCompatActivity {
private static final Logger LOG = LoggerFactory.getLogger("MainActivity");
private ExpandableListView mExpandableListView;
private ExpandableListViewAdapter mExpandableListViewAdapter;
private List<String> mListDataGroup;
private HashMap<String, List<String>> mListDataChild;
PreselectionAplicationUseCases preselectionAplicationUseCases;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initViews();
initListeners();
initObjects();
initListData();
preselectionAplicationUseCases=(PreselectionAplicationUseCases) this;
}
Interface:
public interface PreselectionAplicationUseCases {
void setOnMsgPreselectionChanged(MSG0100.OnMsg100PreselectionChanged listener);
void setMsg100PreselectionAplication(boolean msg100PreselectionAplication);
}
Errors:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: game, PID: 18315
java.lang.RuntimeException: Unable to start activity ComponentInfo{game/game.MainActivity}: java.lang.ClassCastException: game.MainActivity cannot be cast to game.usecases.PreselectionAplicationUseCases
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2327)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2389)
at android.app.ActivityThread.access$800(ActivityThread.java:153)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1305)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5271)
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:902)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:697)
Caused by: java.lang.ClassCastException: game.MainActivity cannot be cast to game.usecases.PreselectionAplicationUseCases
at game.MainActivity.onCreate(MainActivity.java:96)
at android.app.Activity.performCreate(Activity.java:6033)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2280)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2389)
at android.app.ActivityThread.access$800(ActivityThread.java:153)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1305)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5271)
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:902)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:697)
The problem is this: preselectionAplicationUseCases=(PreselectionAplicationUseCases) this;
You cannot cast MainActivity to PreselectionAplicationUseCases since MainActivity or any of it's superclasses don't extend PreselectionAplicationUseCases.
Related
public abstract class MainActivity extends AppCompatActivity {
Button decrement;
Button increment;
TextView counter_view;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Log.i("tag", "onCreate: Created Successfully");
increment=findViewById(R.id.inc_btn);
decrement=findViewById(R.id.dec_btn);
counter_view=findViewById(R.id.counter);
increment.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String cnt_text=counter_view.getText().toString();
int cnt_no= Integer.parseInt(cnt_text);
cnt_no=cnt_no+1;
counter_view.setText(cnt_no+"");
}
});
decrement.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String cnt_text=counter_view.getText().toString();
int cnt_no=Integer.parseInt(cnt_text);
cnt_no=cnt_no-1;
counter_view.setText(cnt_no+"");
}
});
}
Error:
2021-02-10 00:29:06.870 16714-16714/? E/Zygote: v2
2021-02-10 00:29:06.871 16714-16714/? E/Zygote: accessInfo : 0
2021-02-10 00:29:07.017 16714-16714/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.counter_app, PID: 16714
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.counter_app/com.example.counter_app.MainActivity}: java.lang.InstantiationException: java.lang.Class<com.example.counter_app.MainActivity> cannot be instantiated
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2849)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6776)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1518)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1408)
Caused by: java.lang.InstantiationException: java.lang.Class<com.example.counter_app.MainActivity> cannot be instantiated
at java.lang.Class.newInstance(Native Method)
at android.app.Instrumentation.newActivity(Instrumentation.java:1086)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2839)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6776)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1518)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1408)
I suppose this is your first screen/activity/class that is displayed on launch i.e it is your launcher activity. If yes,
the launcher activity cannot be abstract. Because when an app is launched from the home screen on an Android device, the Android OS creates an instance of the activity in the application you have declared to be the launcher activity. And abstract classes can not be instantiated, they can only be sub-classed.
Please remove the word abstract before your class name.
add to your manifest file this line
<activity android:name="your.package.name.MainActivity"/>
Everytime the application gets to my second activity it crashes, giving the error.
My activity:
public class SecondActivity extends AppCompatActivity {
EditText barcodeText = findViewById(R.id.barcodeText);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
IntentFilter filter = new IntentFilter();
filter.addCategory(Intent.CATEGORY_DEFAULT);
filter.addAction(getResources().getString(R.string.activity_intent_filter_action));
registerReceiver(myBroadcastReceiver, filter);
}
private BroadcastReceiver myBroadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
Bundle b = intent.getExtras();
if (action.equals(getResources().getString(R.string.activity_intent_filter_action))) {
try {
displayScanResult(intent);
} catch (Exception e) {
}
}
}
};
private void displayScanResult(Intent initiatingIntent)
{
String decodedSource = initiatingIntent.getStringExtra(getResources().getString(R.string.datawedge_intent_key_source));
String decodedData = initiatingIntent.getStringExtra(getResources().getString(R.string.datawedge_intent_key_data));
String decodedLabelType = initiatingIntent.getStringExtra(getResources().getString(R.string.datawedge_intent_key_label_type));
barcodeText.setText(decodedData);
}
}
Logcat:
07-01 12:37:03.373 349-349/com.example.provatimer E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.provatimer, PID: 349
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.provatimer/com.example.provatimer.SecondActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2236)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5256)
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:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:149)
at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:99)
at android.content.Context.obtainStyledAttributes(Context.java:438)
at androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor(AppCompatDelegateImpl.java:692)
at androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor(AppCompatDelegateImpl.java:659)
at androidx.appcompat.app.AppCompatDelegateImpl.findViewById(AppCompatDelegateImpl.java:479)
at androidx.appcompat.app.AppCompatActivity.findViewById(AppCompatActivity.java:214)
at com.example.provatimer.SecondActivity.<init>(SecondActivity.java:14)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1606)
at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2226)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5256)
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:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
I think it may have something to do with the context in the BroadcastReceiver, but I tried to declare it in the onCreate method but nothing changed.
Maybe I don't initialize correctly the intent in which the data should be stored, if so, how can I do it correctly?
All the Strings should be correct int the string.xml file, if the error may come from that I'll write them.
I think the error is happening here:
EditText barcodeText = findViewById(R.id.barcodeText);
You are invoking findViewById() directly in the class member declaration.
You have invoke findViewById() after setContentView()
EditText barcodeText;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
barcodeText = findViewById(R.id.barcodeText);
}
I tried passing this simple object from MainActivity to Main2Activity by implementing Serializable on the CustomObject. It results in Error. I referred the similar stack overflow questions. Nothing helped.
public class MainActivity extends Activity {
String TAG = "MainActivity";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent i = new Intent(this,Main2Activity.class);
Bundle bundle = new Bundle();
bundle.putSerializable("data",new CustomObject());
//I tried i.putExtra(bundle);
i.putExtra("data",new CustomObject());
startActivity(i);
Log.d(TAG, "onCreate: ");
}
public class CustomObject implements Serializable{
public int i = 0;
public int j = 9;
CustomObject(){
}
}
}
Main2Activity
public class Main2Activity extends Activity {
String TAG = "Main2Activity";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
Intent i = getIntent();
MainActivity.CustomObject c = (MainActivity.CustomObject)i.getSerializableExtra("data");
Log.d(TAG, "onCreate: "+c.i+" "+c.j);
}
}
Error Message:
07-30 13:58:58.352 26489-26489/? E/AndroidRuntime: FATAL EXCEPTION:
main
Process: gct.venkatesh.com.scrshtrebuilt, PID: 26489
java.lang.RuntimeException: Unable to start activity
ComponentInfo{gct.venkatesh.com.scrshtrebuilt/gct.venkatesh.com.scrshtrebuilt.MainActivity}:
java.lang.RuntimeException: Parcelable encountered IOException writing
serializable object (name =
gct.venkatesh.com.scrshtrebuilt.MainActivity$CustomObject)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2684)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2751)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1496)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6186)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)
Caused by: java.lang.RuntimeException: Parcelable encountered IOException writing
serializable object (name =
gct.venkatesh.com.scrshtrebuilt.MainActivity$CustomObject)
at android.os.Parcel.writeSerializable(Parcel.java:1527)
at android.os.Parcel.writeValue(Parcel.java:1475)
at android.os.Parcel.writeArrayMapInternal(Parcel.java:724)
at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1417)
at android.os.Bundle.writeToParcel(Bundle.java:1157)
at android.os.Parcel.writeBundle(Parcel.java:764)
at android.content.Intent.writeToParcel(Intent.java:8703)
at android.app.ActivityManagerProxy.startActivity(ActivityManagerNative.java:3082)
at android.app.Instrumentation.execStartActivity(Instrumentation.java:1520)
at android.app.Activity.startActivityForResult(Activity.java:4229)
at android.app.Activity.startActivityForResult(Activity.java:4187)
at android.app.Activity.startActivity(Activity.java:4526)
at android.app.Activity.startActivity(Activity.java:4494)
at gct.venkatesh.com.scrshtrebuilt.MainActivity.onCreate(MainActivity.java:21)
at android.app.Activity.performCreate(Activity.java:6684)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2637)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2751)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1496)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6186)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)
Caused by: java.io.NotSerializableException:
gct.venkatesh.com.scrshtrebuilt.MainActivity
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1224)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1584)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1549)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1472)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1218)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
at android.os.Parcel.writeSerializable(Parcel.java:1522)
at android.os.Parcel.writeValue(Parcel.java:1475)
at android.os.Parcel.writeArrayMapInternal(Parcel.java:724)
at android.os.BaseBundle.writeToParcelInner(BaseBundle.java:1417)
at android.os.Bundle.writeToParcel(Bundle.java:1157)
at android.os.Parcel.writeBundle(Parcel.java:764)
at android.content.Intent.writeToParcel(Intent.java:8703)
at android.app.ActivityManagerProxy.startActivity(ActivityManagerNative.java:3082)
at android.app.Instrumentation.execStartActivity(Instrumentation.java:1520)
at android.app.Activity.startActivityForResult(Activity.java:4229)
at android.app.Activity.startActivityForResult(Activity.java:4187)
at android.app.Activity.startActivity(Activity.java:4526)
at android.app.Activity.startActivity(Activity.java:4494)
at gct.venkatesh.com.scrshtrebuilt.MainActivity.onCreate(MainActivity.java:21)
at android.app.Activity.performCreate(Activity.java:6684)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2637)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2751)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1496)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6186)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)
by this error in logs:
java.io.NotSerializableException: gct.venkatesh.com.scrshtrebuilt.MainActivity at
MainActivity is not Serializable, i think platform wants MainActivity to be serializable because CustomObject is inner class in MainActivity ,
try to define your CustomObject in a separate local class (separate file)
I write this counter but when I lunch the app get crashed I don't now where the error some help and thank you tell where is the Error here or how can I do code in right way
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
TextView txt = (TextView)findViewById(R.id.textView);
count i;
public void bu1(View view) {
starrtime();
}
public void bu2(View view) {
i.cancel();
}
void starrtime(){
i = new count(100,1000);
i.start();
}
public class count extends CountDownTimer {
public count(long millisInFuture, long countDownInterval) {
super(millisInFuture, countDownInterval);
}
#Override
public void onTick(long millisUntilFinished) {
txt.setText(String.valueOf(millisUntilFinished));
}
#Override
public void onFinish() {
txt.setText("Done");
}
}
}
this my log cat
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.kira.counter, PID: 4598
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.kira.counter/com.example.kira.counter.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.support.v7.app.AppCompatDelegateImplBase.(AppCompatDelegateImplBase.java:116)
at android.support.v7.app.AppCompatDelegateImplV9.(AppCompatDelegateImplV9.java:147)
at android.support.v7.app.AppCompatDelegateImplV11.(AppCompatDelegateImplV11.java:27)
at android.support.v7.app.AppCompatDelegateImplV14.(AppCompatDelegateImplV14.java:50)
at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:201)
at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:181)
at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:521)
at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:190)
at com.example.kira.counter.MainActivity.(MainActivity.java:23)
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1208)
at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2101)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
I believe you can not initialize a TextView before runtime because the views are not set yet. Classes should be capitalized. Try this.
public class MainActivity extends AppCompatActivity{
private TextView txt;
private Count i;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
txt = (TextView)findViewById(R.id.textView);
}
}
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 7 years ago.
I am trying to call a function registerGCM(); from my reg.java class into the MainActivity.java class.
When I use the function from inside the reg.java activity the app works just fine but whenever I call it from inside the MainActivity I get this error
07-28 13:38:38.540 24434-24434/com.example.kmi_dev.fbloginsample E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.kmi_dev.fbloginsample, PID: 24434
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.kmi_dev.fbloginsample/com.example.kmi_dev.fbloginsample.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.kmi_dev.fbloginsample.reg.registerGCM()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
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)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.kmi_dev.fbloginsample.reg.registerGCM()' on a null object reference
at com.example.kmi_dev.fbloginsample.MainActivity.onCreate(MainActivity.java:158)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
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)
Content of the MainActivity where call is being made
public class MainActivity extends Activity {
private static final String TAG = "MainActivity";
private static final String MYPREFERENCES = "myPref";
private CallbackManager callbackManager;
private LoginButton fbLoginButton;
private Button login;
.
.
.
.
GPSTracker gps;
reg GCM_REG;
// flag for Internet connection status
Boolean isInternetPresent = false;
// Connection detector class
ConnectionDetector cd;
SessionManager session;
.
.
String gcmId;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//get global variable class
final GlobalClass globalVariable = (GlobalClass) getApplicationContext();
gcmId = GCM_REG.registerGCM();
Content of registerGCM()
public String registerGCM() {
gcm = GoogleCloudMessaging.getInstance(this);
regId = getRegistrationId(context);
if (TextUtils.isEmpty(regId)) {
registerInBackground();
Log.d("MainActivity",
"registerGCM - successfully registered with GCM server - regId: "
+ regId);
} else {
Toast.makeText(getApplicationContext(),
"RegId already available. RegId: " + regId,
Toast.LENGTH_LONG).show();
}
final GlobalClass globalVariable = (GlobalClass) getApplicationContext();
globalVariable.setGcmRegId(regId);
return regId;
}
public String getRegistrationId(Context context) {
final SharedPreferences prefs = getSharedPreferences(reg.class.getSimpleName(), Context.MODE_PRIVATE);
String registrationId = prefs.getString(REG_ID, "");
if (registrationId.isEmpty()) {
Log.i(TAG, "Registration not found.");
return "";
}
int registeredVersion = prefs.getInt(APP_VERSION, Integer.MIN_VALUE);
int currentVersion = getAppVersion(context);
if (registeredVersion != currentVersion) {
Log.i(TAG, "App version changed.");
return "";
}
return registrationId;
}
Any Idea why I am unable to call this function???
You never initialize GCM_REG. That's why you get a NullPointerException.