无法在android中启动服务错误

Question

I have created a service in my application and called the function that starts the service using a button using onClick in xml but the app crashes. some help will be appreciated. package slide.apptech.com.nav;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.StrictMode;
import android.support.annotation.Nullable;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import android.support.design.widget.FloatingActionButton;

import java.util.ArrayList;
import java.util.Calendar;

import static java.util.Calendar.*;

public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {

private static String TAG = MainActivity.class.getSimpleName();
private Intent myIntent;
Button Refresh;
TextView updated;

//related to main screen list view
ListView lv;
Context context;
ArrayList prgmName;
public static int [] prgmImages={R.drawable.temp,R.drawable.hum,R.drawable.press,R.drawable.amb,R.drawable.alt};
public static String [] prgmNameList={" Temperature:  "," Humidity:  "," Pressure:  "," Ambient Light:"," Altitude:  "};
//GetFromServer gs1=new GetFromServer();
public String [] prgmVal={"1","2","3","4","5"};
public static String [] prgmUnit={" °C"," %"," hPa"," lx"," m"};
//public String datentime=gs1.DateNTime[0];
String datentime;

//boolean variable to indicate if the arrays have been set or not
Boolean arraysset;
GetFromServer gs1;
public ArrayList<String> atList=new ArrayList<String>();
public ArrayList<String> dataList=new ArrayList<String>();


@Override
protected void onCreate(Bundle savedInstanceState) {

    //these lines overite all the warnings by android to restrict large tasks
    StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
    StrictMode.setThreadPolicy(policy);

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    lv = (ListView) findViewById(R.id.listView);
    updated=(TextView)findViewById((R.id.datentime));
    Refresh = (Button) findViewById(R.id.refresh);

    //block related to main screen list view
    //creating a object from getfromserver class to give a request to server
    gs1=new GetFromServer();
    new loadSomeStuff().execute();
    updated.setText(datentime);

    prgmVal[0]=Double.toString(gs1.Temperature[0]);
    prgmVal[1]=Double.toString(gs1.Humidity[0]);
    prgmVal[2]=Double.toString(gs1.Pressure[0]);
    prgmVal[3]=Double.toString(gs1.Ambient[0]);
    prgmVal[4]=Double.toString(gs1.Altitude[0]);
    datentime="Updated on :"+gs1.DateNTime[0];
    context = this;

    //this adapter is defined in custom adapter
    // see class for all the constructors
    lv.setAdapter(new CustomAdapter(MainActivity.this, MainActivity.prgmNameList, MainActivity.prgmImages, prgmVal, MainActivity.prgmUnit));

    //code related to refresh button the main screen find xml in content_main
    Refresh.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            startService(new Intent(getBaseContext(),service.class));
            //Toast.makeText(context, "Please wait!", Toast.LENGTH_LONG).show();
            gs1 = new GetFromServer();
            gs1.sendData();
            gs1.setArray();

            //codeline to start athe service


            prgmVal[0] = Double.toString(gs1.Temperature[0]);
            prgmVal[1] = Double.toString(gs1.Humidity[0]);
            prgmVal[2] = Double.toString(gs1.Pressure[0]);
            prgmVal[3] = Double.toString(gs1.Ambient[0]);
            prgmVal[4] = Double.toString(gs1.Altitude[0]);
            String datentime = "Updated on :" + gs1.DateNTime[0];
            updated.setText(datentime);
            context = MainActivity.this;
            lv.setAdapter(new CustomAdapter(MainActivity.this, MainActivity.prgmNameList, MainActivity.prgmImages, prgmVal, MainActivity.prgmUnit));
            //Toast.makeText(context, "Refreshed!!!", Toast.LENGTH_LONG).show();
        }
    });


    //this code is for a floation button see xml

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent myIntent = new Intent(MainActivity.this,Faq.class);
            startActivity(myIntent);
        }
    });

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}

//this is code related to back button in action bar to close drawer if open else go back to previous activity
@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

//app crash due to following code
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (id == R.id.liConnection) {
        drawer.closeDrawer(GravityCompat.START);
        Intent myIntent = new Intent(MainActivity.this, Connect.class);
        startActivity(myIntent);
    }
    else if (id == R.id.liRanges){
        drawer.closeDrawer(GravityCompat.START);
        Intent myIntent = new Intent(MainActivity.this, Ranges.class);
        startActivity(myIntent);
    }
    else if (id == R.id.liSupport) {
        drawer.closeDrawer(GravityCompat.START);
        Intent myIntent = new Intent(MainActivity.this, Support.class);
        startActivity(myIntent);
    }
    else if (id == R.id.liAbout) {
        drawer.closeDrawer(GravityCompat.START);
        Intent myIntent = new Intent(MainActivity.this, AboutUs.class);
        startActivity(myIntent);
    }
    else if (id == R.id.liRateus) {
        drawer.closeDrawer(GravityCompat.START);
        Intent myIntent = new Intent(MainActivity.this,Rateus.class);
        startActivity(myIntent);
    }
    return true;
}


public void getPosition(int position) {
    if (position == 0) {
        //code specific to first list item
        myIntent = new Intent(MainActivity.this, ChartTemperature.class); //replace connect classs with analysis
        startActivity(myIntent);
    }
    else if (position == 1) {
        //code specific to first list item
        Intent myIntent = new Intent(MainActivity.this, ChartHumidity.class);
        startActivity(myIntent);
    }
    else if (position == 2) {
        //code specific to first list item
        Intent myIntent = new Intent(MainActivity.this, ChartPressure.class);
        startActivity(myIntent);
    }
    else if (position == 3) {
        //code specific to first list item
        Intent myIntent = new Intent(MainActivity.this, ChartAmbient.class);
        startActivity(myIntent);
    }
    else if (position == 4) {
        //code specific to first list item
        Intent myIntent = new Intent(MainActivity.this, ChartAltitude.class);
        startActivity(myIntent);
    }
}

// Method to start the service
public void startService(View view) {
    startService(new Intent(getBaseContext(), service.class));
}

//here we are creating a async task to reduce load on oncreate method
public class loadSomeStuff extends AsyncTask<String, Integer, Void> {

    @Override
    protected Void doInBackground(String... params) {
        // TODO Auto-generated method stub


            try {
                gs1.sendData();
                gs1.setArray();
                prgmVal[0]=Double.toString(gs1.Temperature[0]);
                prgmVal[1]=Double.toString(gs1.Humidity[0]);
                prgmVal[2]=Double.toString(gs1.Pressure[0]);
                prgmVal[3]=Double.toString(gs1.Ambient[0]);
                prgmVal[4]=Double.toString(gs1.Altitude[0]);
                datentime="Updated on :"+gs1.DateNTime[0];

                arraysset = true;
            } catch (Exception e) {
                e.printStackTrace();
            }
        return null;
    }
}

}

service.java

package slide.apptech.com.nav;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.widget.Toast;

/**
 * Created by MOHIT on 17-04-2016.
 */
public class service extends Service{
    //creating a server class object
    GetFromServer gs1;

    //creating a database object
    database record;
    String value;
    boolean tempflag,pressflag,humflag,lightflag;
    double temperature,humidity,pressure,light,max,min;
    NotificationManager manager;
    Notification myNotication;
    Context context;
    MainActivity main;
    public final String UPDATE_DATA = "update";

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        //Toast.makeText(context, "Service Started in onStartCommand", Toast.LENGTH_LONG).show();
        if(intent.getAction().equals(UPDATE_DATA)){
            Toast.makeText(context, "Service Started in onStartCommand", Toast.LENGTH_LONG).show();
            //getandcheck();
        }
        return START_STICKY;
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    public void getandcheck(){

        //getting the values from server
        gs1 = new GetFromServer();
        gs1.sendData();
        gs1.setArray();
        //setting variables to latest sensor values
        temperature = gs1.Temperature[0];
        humidity = gs1.Humidity[0];
        pressure = gs1.Pressure[0];
        light = gs1.Ambient[0];

        record.open();

        //making function calls to setup flags
        checktemp();
        checkhum();
        checkpress();
        checklight();

        //if any flag is true the it means that readings are out of range
        if(tempflag == true){

            String readings = ("Temperature : " + temperature +" °C");


            final Notification.Builder builder = new Notification.Builder(service.this);
            builder.setStyle(new Notification.BigTextStyle(builder)
                    .bigText(readings)
                    .setBigContentTitle("WSstation")
                    .setSummaryText("Alert!!!"))
                    .setContentTitle("WSstation")
                    .setContentText("Your Temperature Readings are out of range")
                    .setSmallIcon(R.drawable.auicon);

            final NotificationManager nm = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            nm.notify(0, builder.build());
        }

        if(pressflag == true){

            String readings = ("Pressure : " + pressure +" hpa");


            final Notification.Builder builder = new Notification.Builder(service.this);
            builder.setStyle(new Notification.BigTextStyle(builder)
                    .bigText(readings)
                    .setBigContentTitle("WSstation")
                    .setSummaryText("Alert!!!"))
                    .setContentTitle("WSstation")
                    .setContentText("Your Pressure Readings are out of range")
                    .setSmallIcon(R.drawable.auicon);

            final NotificationManager nm = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            nm.notify(0, builder.build());
        }

        if(humflag == true){

            String readings = ("Humidity : " + humidity +" %");


            final Notification.Builder builder = new Notification.Builder(service.this);
            builder.setStyle(new Notification.BigTextStyle(builder)
                    .bigText(readings)
                    .setBigContentTitle("WSstation")
                    .setSummaryText("Alert!!!"))
                    .setContentTitle("WSstation")
                    .setContentText("Your Humidity Readings are out of range")
                    .setSmallIcon(R.drawable.auicon);

            final NotificationManager nm = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            nm.notify(0, builder.build());
        }

        if(lightflag == true){

            String readings = ("Ambient Light : " + light +" lx");


            final Notification.Builder builder = new Notification.Builder(service.this);
            builder.setStyle(new Notification.BigTextStyle(builder)
                    .bigText(readings)
                    .setBigContentTitle("WSstation")
                    .setSummaryText("Alert!!!"))
                    .setContentTitle("WSstation")
                    .setContentText("Your Ambient Light Readings are out of range")
                    .setSmallIcon(R.drawable.auicon);

            final NotificationManager nm = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            nm.notify(0, builder.build());
        }
    }

    public void checktemp(){
        //for temperature checking
        value = record.getMax(1);
        max = Double.parseDouble(value);
        value = record.getMin(1);
        min = Double.parseDouble(value);

        if((temperature < min ) || (temperature > max)){
            tempflag = true;
        }
        else{
            tempflag = false;
        }
    }

    public void checkhum(){
        //for humidity checking
        value = record.getMax(3);
        max = Double.parseDouble(value);
        value = record.getMin(3);
        min = Double.parseDouble(value);

        if((humidity < min ) || (humidity > max)){
            humflag = true;
        }
        else{
            humflag = false;
        }
    }

    public void checkpress(){
        //for pressure checking
        value = record.getMax(2);
        max = Double.parseDouble(value);
        value = record.getMin(2);
        min = Double.parseDouble(value);

        if((pressure < min ) || (pressure > max)){
            pressflag = true;
        }
        else{
            pressflag = false;
        }
    }

    public void checklight(){
        //for ambient light checking
        value = record.getMax(4);
        max = Double.parseDouble(value);
        value = record.getMin(4);
        min = Double.parseDouble(value);

        if((light < min ) || (light > max)){
            lightflag = true;
        }
        else{
            lightflag = false;
        }
    }

    /*@Override
    public void onCreate() {
        super.onCreate();
        Toast.makeText(context, "Service Started in oncreate", Toast.LENGTH_LONG).show();
    }*/

}

content_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="slide.apptech.com.nav.MainActivity"
    tools:showIn="@layout/app_bar_main">

    <RelativeLayout
        android:id="@+id/mainContent"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#004D40">



        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:tools="http://schemas.android.com/tools"
            android:background="#004D40"
            android:layout_width="match_parent"
            android:layout_height="fill_parent"
            android:orientation="vertical"
            android:paddingBottom="@dimen/activity_vertical_margin"
            android:paddingLeft="@dimen/activity_horizontal_margin"
            android:paddingRight="@dimen/activity_horizontal_margin"
            android:paddingTop="@dimen/activity_vertical_margin"
            tools:context=".Home"
            android:layout_alignParentTop="true"
            android:layout_alignParentStart="true">

            <!--<TextView
                android:id="@+id/textView1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textSize="25dp"
                android:textStyle="bold"
                android:text=" Computer Languages..." />
                -->

            <ListView
                android:paddingTop="60dp"
                android:id="@+id/listView"
                android:layout_width="fill_parent"
                android:layout_height="376dp"
                android:layout_above="@+id/datentime">
            </ListView>

            <TextView
                android:paddingTop="20dp"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textAppearance="?android:attr/textAppearanceSmall"
                android:text="Updated:"
                android:textColor="#FFEB3B"
                android:id="@+id/datentime"
                android:layout_gravity="center_horizontal" />

            <Button
                style="?android:attr/buttonStyleSmall"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Refresh"
                android:id="@+id/refresh"
                android:layout_gravity="center_horizontal"
                android:onClick="startService"/>


        </LinearLayout>

    </RelativeLayout>

</RelativeLayout>

logcat

04-20 20:15:18.623 27500-27500/slide.apptech.com.nav E/MotionRecognitionManager: mSContextService = null
04-20 20:15:18.628 27500-27500/slide.apptech.com.nav E/MotionRecognitionManager: motionService = com.samsung.android.motion.IMotionRecognitionService$Stub$Proxy@28c858d
04-20 20:15:24.578 27500-27500/slide.apptech.com.nav E/AndroidRuntime: FATAL EXCEPTION: main
                                                                       Process: slide.apptech.com.nav, PID: 27500
                                                                       java.lang.RuntimeException: Unable to start service slide.apptech.com.nav.service@1aa1fa82 with Intent { cmp=slide.apptech.com.nav/.service }: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
                                                                           at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:3978)
                                                                           at android.app.ActivityThread.access$2300(ActivityThread.java:211)
                                                                           at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1803)
                                                                           at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                           at android.os.Looper.loop(Looper.java:145)
                                                                           at android.app.ActivityThread.main(ActivityThread.java:6912)
                                                                           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:1404)
                                                                           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
                                                                        Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
                                                                           at slide.apptech.com.nav.service.onStartCommand(service.java:33)
                                                                           at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:3961)
                                                                           at android.app.ActivityThread.access$2300(ActivityThread.java:211) 
                                                                           at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1803) 
                                                                           at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                           at android.os.Looper.loop(Looper.java:145) 
                                                                           at android.app.ActivityThread.main(ActivityThread.java:6912) 
                                                                           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:1404) 
                                                                           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199) 

Answer 1

The intent you are checking in service.onStartCommand does not have an action. Change this

if(intent.getAction().equals(UPDATE_DATA)){
    Toast.makeText(context, "Service Started in onStartCommand", Toast.LENGTH_LONG).show();
    //getandcheck();
}

into this

if(intent.getAction() != null && intent.getAction().equals(UPDATE_DATA)){
    Toast.makeText(context, "Service Started in onStartCommand", Toast.LENGTH_LONG).show();
    //getandcheck();
}

UPDATE
To still show the toast you could put an extra boolean in your intent and check for this in your service. Start your service like this

startService(new Intent(getBaseContext(),service.class).putExtra("show_toast", true));

And check for it in your service like this

if (intent.getBooleanExtra("show_toast", false)) {
    Toast.makeText(context, "Service Started in onStartCommand", Toast.LENGTH_LONG).show();
    //getandcheck();
}

Answer 2

Looks like you didn't specify an action for the intent and you are getting a null pointer because of that. Also be sure that you check the String constant against the object value to avoid null pointer exceptions.

UPDATE_DATA.equals(intent.getAction())