java - How to create a flash light as well as strobe effect. Need help to fix strobe effect -

i trying create flash light application contains strobe function. have achieved flash light on/off effect running trouble strobe effect. whenever try create strobe effect application crashes. if remove that, works fine.

i have 1 activity seekbar @ top , on/off switch @ center. want achieve if user clicks on/off button flash light should toggle on/off if seekbar @ top @ 0. if user increase value in seekbar flash light should start strobe accordingly , if user move value 0 flashlight should remain constant. please me fix error.

log cat

07-23 16:54:12.610: w/dalvikvm(21210): threadid=11: thread exiting uncaught exception (group=0x40c15a68) 07-23 16:54:12.610: e/androidruntime(21210): fatal exception: thread-2373 07-23 16:54:12.610: e/androidruntime(21210): java.lang.runtimeexception: fail connect camera service 07-23 16:54:12.610: e/androidruntime(21210):    @ android.hardware.camera.native_setup(native method) 07-23 16:54:12.610: e/androidruntime(21210):    @ android.hardware.camera.<init>(camera.java:365) 07-23 16:54:12.610: e/androidruntime(21210):    @ android.hardware.camera.open(camera.java:340) 07-23 16:54:12.610: e/androidruntime(21210):    @ com.shyam.flashlight.strobecontroller.run(strobecontroller.java:29) 07-23 16:54:12.610: e/androidruntime(21210):    @ java.lang.thread.run(thread.java:856) 

flashlight.java

public class flashlight extends activity {  imagebutton btnswitch; private camera camera; private boolean isflashon; private boolean hasflash; parameters params; mediaplayer mp;  strobecontroller runner; thread bw;  @suppresswarnings("deprecation") @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     requestwindowfeature(window.feature_no_title);     setcontentview(r.layout.activity_flash_light);      btnswitch = (imagebutton) findviewbyid(r.id.btnswitch);      runner = strobecontroller.getinstance();      bw = new thread(runner);     bw.start();      hasflash = getapplicationcontext().getpackagemanager().hassystemfeature(packagemanager.feature_camera_flash);      if (!hasflash) {         alertdialog alert = new alertdialog.builder(flashlight.this).create();         alert.settitle("error");         alert.setmessage("sorry, device doesn't support flash light!");         alert.setbutton("ok", new dialoginterface.onclicklistener() {             public void onclick(dialoginterface dialog, int which) {                 finish();             }         });         alert.show();         return;     }      getcamera();      togglebuttonimage();      btnswitch.setonclicklistener(new view.onclicklistener() {          @override         public void onclick(view v) {             /*if (isflashon) {                 turnoffflash();             } else {                 turnonflash();             }*/              if (isflashon) {                 bw = new thread(runner);                 bw.start();                 isflashon = false;             } else {                 isflashon = true;                 runner.requeststop = true;             }          }     });      final seekbar skbar = (seekbar) findviewbyid(r.id.volume_bar);     skbar.setonseekbarchangelistener(new onseekbarchangelistener() {          @override         public void onstoptrackingtouch(seekbar seekbar) { }          @override         public void onstarttrackingtouch(seekbar seekbar) { }          @override         public void onprogresschanged(seekbar seekbar, int progress, boolean fromuser) {             runner.delay = 101 - progress;             runner.delayoff = 101 - progress;         }     });  }  private void getcamera() {     if (camera == null) {         try {             camera = camera.open();             params = camera.getparameters();         } catch (runtimeexception e) {             log.e("camera error. failed open. error: ", e.getmessage());         }     } }  private void turnonflash() {     if (!isflashon) {         if (camera == null || params == null) {             return;         }          playsound();          params = camera.getparameters();         params.setflashmode(parameters.flash_mode_torch);         camera.setparameters(params);         camera.startpreview();         isflashon = true;          togglebuttonimage();     } }  private void turnoffflash() {     if (isflashon) {         if (camera == null || params == null) {             return;         }          playsound();          params = camera.getparameters();         params.setflashmode(parameters.flash_mode_off);         camera.setparameters(params);         camera.stoppreview();         isflashon = false;          togglebuttonimage();     } }  private void playsound() {     if (isflashon) {         mp = mediaplayer.create(flashlight.this, r.raw.light_switch_off);     } else {         mp = mediaplayer.create(flashlight.this, r.raw.light_switch_on);     }     mp.setoncompletionlistener(new oncompletionlistener() {          @override         public void oncompletion(mediaplayer mp) {             mp.release();         }     });     mp.start(); }  private void togglebuttonimage() {     if (isflashon) {         btnswitch.setimageresource(r.drawable.btn_switch_on);     } else {         btnswitch.setimageresource(r.drawable.btn_switch_off);     } }  @override public void onbackpressed() {     super.onbackpressed();      params = camera.getparameters();     params.setflashmode(parameters.flash_mode_off);     camera.setparameters(params);     camera.stoppreview();     isflashon = false;      if (camera != null) {         camera.release();         camera = null;     }     log.d("camera", "back pressed"); }  } 

strobecontroller.java

public class strobecontroller implements runnable {  protected strobecontroller() { }  public static strobecontroller getinstance() {     return (instance == null ? instance = new strobecontroller() : instance); }  private static strobecontroller instance; public volatile boolean requeststop = false; public volatile boolean isrunning = false; public volatile int delay = 10; public volatile int delayoff = 500; public volatile string errormessage = "";  @override public void run() {     if (isrunning)         return;      requeststop = false;     isrunning = true;      camera cam = camera.open();      parameters pon = cam.getparameters(), poff = cam.getparameters();      pon.setflashmode(camera.parameters.flash_mode_torch);     poff.setflashmode(camera.parameters.flash_mode_off);      while (!requeststop) {         try {             cam.setparameters(pon);             thread.sleep(delay);             cam.setparameters(poff);             thread.sleep(delayoff);         } catch (interruptedexception ex) {          } catch (runtimeexception ex) {             requeststop = true;             errormessage = "error setting camera flash status. device may unsupported.";         }     }      cam.release();      isrunning = false;     requeststop = false; }  } 

i notice exception being thrown @ line 29:

at com.shyam.flashlight.strobecontroller.run(strobecontroller.java:29)

is line 29 camera cam = camera.open();?

you have correct permissions described here? also, trying open null camera? @ line 29 in strobecontroller class.