Now I have an activity by which I want to call a Service named MyService.
I wrote

```
Intent i =new Intent(this,MyService.class); 
i.putExtra("s", s);
startService(i);

```

in the activity,while my MyService.java typed

```
@Override

public void onStart(Intent intent, int startId)
{
    // TODO: Implement this method
    super.onStart(intent, startId);
    connect(intent);
    try{
        connect(intent);
        Intent i=new Intent();
        s=i.getStringExtra("s").toString();
        sendData(s);
    } catch(IOError e)
    {
       Toast.makeText(getBaseContext(), e.getMessage(), Toast.LENGTH_SHORT).show();
    }
}

```

But when I run the code, I get a NullPointException on the line

`s=i.getStringExtra("s").toString();`

Please who can tell me where I have gone wrong,and what should I do,thanks.

Then, I got the log of my app whose package name is "com.TsyQi.Sensor"

---

java.lang.RuntimeException: Unable to start service com.TsyQi.Sensor.MyService@26abf3ed with Intent { cmp=com.TsyQi.Sensor/.MyService }: 

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.toString()' on a null object reference

```
at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2882)
at android.app.ActivityThread.access$2100(ActivityThread.java:147)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1379)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5233)
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 'java.lang.String java.lang.String.toString()' on a null object reference

```
at com.TsyQi.Sensor.MyService.onStart(MyService.java:227)
at android.app.IntentService.onStartCommand(IntentService.java:130)
at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2865)
... 9 more

```

---