java - Android cameraSource.stop() causing app to freeze -

i building app has qr scanner using google vision api. having trouble stopping camera after qr code read. flow mainactivity -> qractivity once qr-code received detection app should return main activity.

if not call camerasource.release() works fine device heats lot , has significant impact on battery drain. if release camera source mainactivity becomes un-responsive , app crash.

why becoming unresponsive? , correct place release camera source?

qractivity

@override protected void oncreate(bundle savedinstancestate) {      super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_qr);     cancelbtn = (button) findviewbyid(r.id.cancel_button);     cancelbtn.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {             onbackpressed();         }     });      new qrreader(this); } 

qrreader class

public class qrreader {      private static final string tag = "qrreader";      private surfaceview cameraview;     private textview barcodeinfo;     private barcodedetector barcodedetector;     private camerasource camerasource;     private activity mactivity;     private accesspointcredentials barcodedata;      public qrreader(activity activity) {         this.mactivity = activity;          cameraview = (surfaceview) mactivity.findviewbyid(r.id.camera_view);         barcodeinfo = (textview) mactivity.findviewbyid(r.id.code_info);          barcodedetector =                 new barcodedetector.builder(mactivity)                         .setbarcodeformats(barcode.qr_code)                         .build();          camerasource = new camerasource                 .builder(mactivity, barcodedetector)                 .setautofocusenabled(true)                 .build();          cameraview.getholder().addcallback(new surfaceholder.callback() {              @override             public void surfacecreated(surfaceholder holder) {                  camerasource = new camerasource                         .builder(mactivity, barcodedetector)                         .setautofocusenabled(true)                         .setfacing(0)                         .build();                 try {                                       camerasource.start(cameraview.getholder());                  } catch (exception ioe) {                     ioe.printstacktrace();                 }             }              @override             public void surfacechanged(surfaceholder holder, int format, int width, int height) {             }              @override             public void surfacedestroyed(surfaceholder holder) {                   // log.i(tag, "surfacedestroyed: stopping camera source");                    // camerasource.release();             }         });          barcodedetector.setprocessor(new detector.processor<barcode>() {             @override             public void release() {                 log.i(tag, "release: ");             }              @override             public void receivedetections(detector.detections<barcode> detections) {                 final sparsearray<barcode> barcodes = detections.getdetecteditems();                  if (barcodes.size() != 0) {                      log.i(tag, "received barcode");                     barcodeinfo.post(new runnable() {    // use post method of textview                         public void run() {                             barcodeinfo.settext(barcodes.valueat(0).displayvalue);                          }                     });                     gson g = new gson();                     try {                         barcodedata = g.fromjson(barcodes.valueat(0).rawvalue, accesspointcredentials.class);                     } catch (exception e) {                         barcodedata = new accesspointcredentials();                         barcodedata.setssid(barcodes.valueat(0).rawvalue);                         barcodedata.setpass(null);                         e.printstacktrace();                     }                      connecttowifi(barcodedata);                      // camerasource.release causes app freeze                      // camerasource.release();                 }             }         });     }      private void connecttowifi(final accesspointcredentials credentials) {                  //wificonnect code      }  } 

it's been 3 months stumbled on same problem , figure out. code inside receivedetections method running on different thread if want needs ui thread need post handler:

handler handler = new handler(looper.getmainlooper()); handler.post(new runnable() {      @override      public void run() {          camerasource.release();      } });