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$MethodAndArgsCaller.run(ZygoteInit.java:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
I think it may have something to do with the context in the BroadcastReceiver, but I tried to declare it in the onCreate method but nothing changed.
Maybe I don't initialize correctly the intent in which the data should be stored, if so, how can I do it correctly?
All the Strings should be correct int the string.xml file, if the error may come from that I'll write them.
I think the error is happening here:
EditText barcodeText = findViewById(R.id.barcodeText);
You are invoking findViewById() directly in the class member declaration.
You have invoke findViewById() after setContentView()
EditText barcodeText;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
barcodeText = findViewById(R.id.barcodeText);
}
I am facing issue with my code.I am getting RuntimeException.Kindly please do help me with this.
I'm getting the following error log :
06-17 18:11:32.646 13750-13750/? E/Zygote: v2
06-17 18:11:32.646 13750-13750/? E/Zygote: accessInfo : 0
06-17 18:11:33.226 13750-13750/com.example.cocol.timisoara2021 E/MotionRecognitionManager: mSContextService = android.hardware.scontext.ISContextService$Stub$Proxy#f847827
06-17 18:11:33.226 13750-13750/com.example.cocol.timisoara2021 E/MotionRecognitionManager: motionService = com.samsung.android.motion.IMotionRecognitionService$Stub$Proxy#d2d3ad4
06-17 18:11:33.226 13750-13750/com.example.cocol.timisoara2021 E/MotionRecognitionManager: motionService = com.samsung.android.motion.IMotionRecognitionService$Stub$Proxy#d2d3ad4
06-17 18:11:36.566 13750-14348/com.example.cocol.timisoara2021 E/GooglePlayServicesUtil: The Google Play services resources were not found. Check your project configuration to ensure that the resources are included.
06-17 18:11:36.666 13750-13750/com.example.cocol.timisoara2021 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.cocol.timisoara2021, PID: 13750
java.lang.RuntimeException: Unable to resume activity {com.example.cocol.timisoara2021/com.example.cocol.timisoara2021.Main2Activity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.wikitude.common.orientation.internal.a.a()' on a null object reference
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4226)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4328)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3427)
at android.app.ActivityThread.access$1100(ActivityThread.java:229)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1821)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:7407)
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 com.wikitude.common.orientation.internal.a.a()' on a null object reference
at com.wikitude.architect.ArchitectView.onResume(ProGuard:818)
at com.example.cocol.timisoara2021.Main2Activity.onResume(Main2Activity.java:59)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1287)
at android.app.Activity.performResume(Activity.java:7015)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4215)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4328)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3427)
at android.app.ActivityThread.access$1100(ActivityThread.java:229)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1821)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:7407)
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)
And here is the line 53:architectView.onResume();
And the code:
package com.example.cocol.timisoara2021;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import com.wikitude.architect.ArchitectStartupConfiguration;
import com.wikitude.architect.ArchitectView;
public class Main2Activity extends AppCompatActivity {
private ArchitectView architectView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
this.architectView = (ArchitectView) this.findViewById(R.id.architectView);
final ArchitectStartupConfiguration config = new ArchitectStartupConfiguration();
config.setLicenseKey("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");
this.architectView.onCreate(config);
}
protected void OnPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
architectView.onPostCreate();
try {
this.architectView.load("file:///android_asset/POI/index.html");
}catch (Exception e) {
}
}
#Override
protected void onPause() {
super.onPause();
architectView.onPause();
}
#Override
protected void onResume() {
super.onResume();
architectView.onResume();
}
#Override
protected void onDestroy() {
super.onDestroy();
architectView.onDestroy();
}
}
How can I fix this ?
Your onPostCreate method has an uppercase "O". Because of this i assume it is never called which means that the ArchitectView is in an invalid state when you call architectView.onResume.
Try:
#Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
architectView.onPostCreate();
try {
this.architectView.load("file:///android_asset/POI/index.html");
}catch (Exception e) {
}
}
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);
}
}
I have a mainActivity which has a button named monitoring. When I press the button it should show the nearby beacons. When I press the button an error shows up which say's my application stopped working. Here is the code of the button activity:
public class MonitoringBeacons extends AppCompatActivity {
private ProximityManagerContract proximityManager;
ListAdapter beaconsAdapter;
ListView listView;
List<String> beaconsList = new ArrayList<String>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_monitoring_beacons);
KontaktSDK.initialize("kasjdhioasjkdoasdjo");
proximityManager = new ProximityManager(this);
proximityManager.setEddystoneListener(createEddystoneListener());
setAdapter();
listView.setOnItemClickListener(
new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
String beacon = String.valueOf(adapterView.getItemAtPosition(position));
Toast.makeText(MonitoringBeacons.this, beacon, Toast.LENGTH_SHORT).show();
}
}
);
}
protected void setAdapter() {
if(beaconsList.isEmpty()) {
Toast.makeText(MonitoringBeacons.this, "No beacons found", Toast.LENGTH_SHORT).show();
return ;
}
beaconsAdapter = new CustomListAdapter(this, beaconsList);
listView = (ListView) findViewById(R.id.listView);
listView.setAdapter(beaconsAdapter);
}
#Override
protected void onStart() {
super.onStart();
startScanning();
}
#Override
protected void onStop() {
proximityManager.stopScanning();
super.onStop();
}
#Override
protected void onDestroy() {
proximityManager.disconnect();
proximityManager = null;
super.onDestroy();
}
private void startScanning() {
proximityManager.connect(new OnServiceReadyListener() {
#Override
public void onServiceReady() {
proximityManager.startScanning();
}
});
}
private EddystoneListener createEddystoneListener() {
return new SimpleEddystoneListener() {
#Override
public void onEddystoneDiscovered(IEddystoneDevice eddystone, IEddystoneNamespace namespace) {
beaconsList.add(eddystone.getUniqueId());
setAdapter();
}
#Override
public void onEddystoneLost(IEddystoneDevice eddystone, IEddystoneNamespace namespace) {
beaconsList.remove(eddystone.getUniqueId());
setAdapter();
}
};
}
}
and the code of CustomListAdapter:
public class CustomListAdapter extends BaseAdapter {
private List<String> beaconsList;
private Activity activity;
private LayoutInflater inflater;
public CustomListAdapter(Activity activity, List<String> beaconsList) {
this.activity = activity;
this.beaconsList = beaconsList;
}
#Override
public int getCount() {
return beaconsList.size();
}
#Override
public Object getItem(int location) {
return beaconsList.get(location);
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if (inflater == null)
inflater = (LayoutInflater) activity
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if (convertView == null)
convertView = inflater.inflate(R.layout.custom_row, null);
String singleBeaconItem = String.valueOf(getItem(position));
TextView beaconText = (TextView) convertView.findViewById(R.id.BeaconText);
ImageView beaconImage = (ImageView) convertView.findViewById(R.id.BeaconImage);
beaconText.setText(singleBeaconItem);
beaconImage.setImageResource(R.drawable.tough_beacon_1);
return convertView;
}
}
Ideally when I press the button the nearby beacons should be appeared as a list, and when a beacon is discovered or lost the list should automaticaly be updated.
EDITED
Stack trace in LogCat
--------- beginning of crash
08-06 17:02:15.276 2559-2559/com.example.panagiotis.beaconsproject E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.panagiotis.beaconsproject, PID: 2559
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.panagiotis.beaconsproject/com.example.panagiotis.beaconsproject.MonitoringBeacons}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setOnItemClickListener(android.widget.AdapterView$OnItemClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setOnItemClickListener(android.widget.AdapterView$OnItemClickListener)' on a null object reference
at com.example.panagiotis.beaconsproject.MonitoringBeacons.onCreate(MonitoringBeacons.java:44)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
08-06 17:02:18.087 2559-2559/com.example.panagiotis.beaconsproject I/Process: Sending signal. PID: 2559 SIG: 9
08-06 17:02:22.298 3433-3433/com.example.panagiotis.beaconsproject W/System: ClassLoader referenced unknown path: /data/app/com.example.panagiotis.beaconsproject-1/lib/x86
08-06 17:02:22.455 3433-3433/com.example.panagiotis.beaconsproject W/System: ClassLoader referenced unknown path: /data/app/com.example.panagiotis.beaconsproject-1/lib/x86
08-06 17:02:22.604 3433-3433/com.example.panagiotis.beaconsproject W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
08-06 17:02:22.715 3433-3460/com.example.panagiotis.beaconsproject D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true
[ 08-06 17:02:22.718 3433: 3433 D/ ]
HostConnection::get() New Host Connection established 0xaa9a71c0, tid 3433
[ 08-06 17:02:22.754 3433: 3460 D/ ]
HostConnection::get() New Host Connection established 0xaa9a6920, tid 3460
08-06 17:02:22.768 3433-3460/com.example.panagiotis.beaconsproject I/OpenGLRenderer: Initialized EGL, version 1.4
08-06 17:02:24.070 3433-3460/com.example.panagiotis.beaconsproject E/Surface: getSlotFromBufferLocked: unknown buffer: 0xaa9b17f0
08-06 17:02:26.685 3433-3433/com.example.panagiotis.beaconsproject W/ViewRootImpl: Cancelling event due to no window focus: MotionEvent { action=ACTION_CANCEL, actionButton=0, id[0]=0, x[0]=397.5, y[0]=956.6797, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=70853, downTime=67680, deviceId=0, source=0x1002 }
08-06 17:02:26.685 3433-3433/com.example.panagiotis.beaconsproject W/ViewRootImpl: Cancelling event due to no window focus: MotionEvent { action=ACTION_CANCEL, actionButton=0, id[0]=0, x[0]=397.5, y[0]=956.6797, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=70853, downTime=67680, deviceId=0, source=0x1002 }
08-06 17:02:26.686 3433-3433/com.example.panagiotis.beaconsproject W/ViewRootImpl: Cancelling event due to no window focus: MotionEvent { action=ACTION_CANCEL, actionButton=0, id[0]=0, x[0]=397.5, y[0]=956.6797, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=70853, downTime=67680, deviceId=0, source=0x1002 }
08-06 17:02:26.686 3433-3433/com.example.panagiotis.beaconsproject W/ViewRootImpl: Cancelling event due to no window focus: MotionEvent { action=ACTION_CANCEL, actionButton=0, id[0]=0, x[0]=397.5, y[0]=956.6797, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=70853, downTime=67680, deviceId=0, source=0x1002 }
08-06 17:02:28.817 3433-3460/com.example.panagiotis.beaconsproject E/Surface: getSlotFromBufferLocked: unknown buffer: 0xaa9b17f0
08-06 17:02:29.373 3433-3460/com.example.panagiotis.beaconsproject E/Surface: getSlotFromBufferLocked: unknown buffer: 0xb40938f0
08-06 17:02:29.375 3433-3460/com.example.panagiotis.beaconsproject D/OpenGLRenderer: endAllStagingAnimators on 0xa1d53580 (RippleDrawable) with handle 0xa203f910
08-06 17:02:30.806 3433-3460/com.example.panagiotis.beaconsproject E/Surface: getSlotFromBufferLocked: unknown buffer: 0xb4094e60
08-06 17:02:32.811 3433-3460/com.example.panagiotis.beaconsproject E/Surface: getSlotFromBufferLocked: unknown buffer: 0xb40938f0
08-06 17:02:35.874 3433-3433/com.example.panagiotis.beaconsproject D/AndroidRuntime: Shutting down VM
08-06 17:02:35.874 3433-3433/com.example.panagiotis.beaconsproject E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.panagiotis.beaconsproject, PID: 3433
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.panagiotis.beaconsproject/com.example.panagiotis.beaconsproject.MonitoringBeacons}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setOnItemClickListener(android.widget.AdapterView$OnItemClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setOnItemClickListener(android.widget.AdapterView$OnItemClickListener)' on a null object reference
at com.example.panagiotis.beaconsproject.MonitoringBeacons.onCreate(MonitoringBeacons.java:44)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
08-06 17:02:39.204 3433-3433/com.example.panagiotis.beaconsproject I/Process: Sending signal. PID: 3433 SIG: 9
Any idea?
The stacktrace explains what is happening.
When this line of code executes:
listView.setOnItemClickListener(...
The listView has not yet been initialized, so it is null. This causes a NullPointerException.
That variable is initialized in the setAdapter() method, but it may not be because the method exits early if beaconsList.isEmpty() evaluates to true.
The simple solution is to move the code that initializes listView to top of that method.