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Failed to create service java.lang.NullPointerException

I am implementing a sensorEventListener which, when shaken, changes the ringer mode. I use the service so that I can change the call mode outside of external activity when I like. This is my code for the service I use -

package com.nadeem.shakeit; import android.app.Service; import android.content.Intent; import android.hardware.Sensor; import android.hardware.SensorEvent; import android.hardware.SensorEventListener; import android.hardware.SensorManager; import android.media.AudioManager; import android.os.IBinder; public class service extends Service implements SensorEventListener { private SensorManager sensorManager; private long lastUpdate; AudioManager am; @Override public void onCreate() { super.onCreate(); sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_NORMAL); } /*@Override public int onStartCommand(Intent intent, int flags, int startId) { if (intent == null) { sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_NORMAL); } return Service.START_REDELIVER_INTENT; }*/ @Override public void onDestroy() { sensorManager.unregisterListener(this); } @Override public void onSensorChanged(SensorEvent event) { if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) { getAccelerometer(event); } } private void getAccelerometer(SensorEvent event) { float[] values = event.values; // Movement float x = values[0]; float y = values[1]; float z = values[2]; float accelationSquareRoot = (x * x + y * y + z * z) / (SensorManager.GRAVITY_EARTH * SensorManager.GRAVITY_EARTH); long actualTime = System.currentTimeMillis(); if (accelationSquareRoot >= 5) // { if (actualTime - lastUpdate < 200) { return; } lastUpdate = actualTime; int ringerMode = am.getRingerMode(); if (ringerMode == AudioManager.RINGER_MODE_NORMAL) { am.setRingerMode(AudioManager.RINGER_MODE_VIBRATE); } else if (ringerMode == AudioManager.RINGER_MODE_VIBRATE) { am.setRingerMode(AudioManager.RINGER_MODE_SILENT); } else { am.setRingerMode(AudioManager.RINGER_MODE_NORMAL); } } } @Override public void onAccuracyChanged(Sensor sensor, int accuracy) { } @Override public IBinder onBind(Intent intent) { // TODO for communication return IBinder implementation return null; } }

when I open the application, the action is forcibly closed. Logcat shows: -

 07-15 12:04:02.800: E/AndroidRuntime(22092): FATAL EXCEPTION: main 07-15 12:04:02.800: E/AndroidRuntime(22092): java.lang.RuntimeException: Unable to create service com.nadeem.shakeit.service: java.lang.NullPointerException 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2076) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.app.ActivityThread.access$2500(ActivityThread.java:123) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:993) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.os.Handler.dispatchMessage(Handler.java:99) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.os.Looper.loop(Looper.java:130) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.app.ActivityThread.main(ActivityThread.java:3835) 07-15 12:04:02.800: E/AndroidRuntime(22092): at java.lang.reflect.Method.invokeNative(Native Method) 07-15 12:04:02.800: E/AndroidRuntime(22092): at java.lang.reflect.Method.invoke(Method.java:507) 07-15 12:04:02.800: E/AndroidRuntime(22092): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858) 07-15 12:04:02.800: E/AndroidRuntime(22092): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 07-15 12:04:02.800: E/AndroidRuntime(22092): at dalvik.system.NativeStart.main(Native Method) 07-15 12:04:02.800: E/AndroidRuntime(22092): Caused by: java.lang.NullPointerException 07-15 12:04:02.800: E/AndroidRuntime(22092): at com.nadeem.shakeit.service.onCreate(service.java:21) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2066) 07-15 12:04:02.800: E/AndroidRuntime(22092): ... 10 more

Edit-After, by creating an instance of sensorManager again, I get a nullPointerException. Stack trace -

 07-15 12:35:45.280: E/AndroidRuntime(22469): FATAL EXCEPTION: main 07-15 12:35:45.280: E/AndroidRuntime(22469): java.lang.NullPointerException 07-15 12:35:45.280: E/AndroidRuntime(22469): at com.nadeem.shakeit.service.getAccelerometer(service.java:64) 07-15 12:35:45.280: E/AndroidRuntime(22469): at com.nadeem.shakeit.service.onSensorChanged(service.java:43) 07-15 12:35:45.280: E/AndroidRuntime(22469): at android.hardware.SensorManager$ListenerDelegate$1.handleMessage(SensorManager.java:529) 07-15 12:35:45.280: E/AndroidRuntime(22469): at android.os.Handler.dispatchMessage(Handler.java:99) 07-15 12:35:45.280: E/AndroidRuntime(22469): at android.os.Looper.loop(Looper.java:130) 07-15 12:35:45.280: E/AndroidRuntime(22469): at android.app.ActivityThread.main(ActivityThread.java:3835) 07-15 12:35:45.280: E/AndroidRuntime(22469): at java.lang.reflect.Method.invokeNative(Native Method) 07-15 12:35:45.280: E/AndroidRuntime(22469): at java.lang.reflect.Method.invoke(Method.java:507) 07-15 12:35:45.280: E/AndroidRuntime(22469): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858) 07-15 12:35:45.280: E/AndroidRuntime(22469): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 07-15 12:35:45.280: E/AndroidRuntime(22469): at dalvik.system.NativeStart.main(Native Method)
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3 answers

sensorManager initialized. You are missing something similar in onCreate()

 sensorManager=(SensorManager) getSystemService(...);
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Initialize the sensorManager variable.

 sensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
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You just declared the SensorManager reference variable, it currently contains a null reference, where did you create it?

 private SensorManager sensorManager;

Calling any method in this null reference will NullPointerException :

 sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_NORMAL);

You need to initialize it in onCreate() :

 sensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);

Even your AudioManager am; refers to null , you need to initialize it before calling any methods on it.

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Source: https://habr.com/ru/post/1491375/

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