please excuse me if simple resolve. i'm new debugging , resolving situations this. i'm not sure begin start tracking down issue , sure of architecture involved. happens sporadically , seems more of race condition based on how fast try refire animation after previous animation ended. appreciate pointers , learn little.
08-08 09:26:01.410 30626-30626/com.myapp.myappname e/androidruntime: fatal exception: main process: com.myapp.myappname, pid: 30626 java.lang.nullpointerexception: attempt invoke interface method 'void android.animation.animator$animatorlistener.onanimationend(android.animation.animator)' on null object reference @ android.animation.valueanimator.endanimation(valueanimator.java:1239) @ android.animation.valueanimator.cancel(valueanimator.java:1140) @ android.animation.objectanimator.animatevalue(objectanimator.java:974) @ android.animation.valueanimator.animationframe(valueanimator.java:1384) @ android.animation.valueanimator.doanimationframe(valueanimator.java:1427) @ android.animation.valueanimator$animationhandler.doanimationframe(valueanimator.java:759) @ android.animation.valueanimator$animationhandler$1.run(valueanimator.java:801) @ android.view.choreographer$callbackrecord.run(choreographer.java:920) @ android.view.choreographer.docallbacks(choreographer.java:695) @ android.view.choreographer.doframe(choreographer.java:628) @ android.view.choreographer$framedisplayeventreceiver.run(choreographer.java:906) @ android.os.handler.handlecallback(handler.java:739) @ android.os.handler.dispatchmessage(handler.java:95) @ android.os.looper.loop(looper.java:158) @ android.app.activitythread.main(activitythread.java:7229) @ java.lang.reflect.method.invoke(native method) @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:1230) @ com.android.internal.os.zygoteinit.main(zygoteinit.java:1120) here reference code regarding mechanics of causing npe. have start , stop button register , unregister light sensor. when registered , light event happens allow 1 call @ time via lock , startup handler/runnable. when animation ends/completes lock released execution in light event handler.
where see npe happening sporadically when go press start after prior stop issued. happens rarely, right @ boundary of stop happening , start happening again.
// on startup of app, prepare runnable runnablealpha = new runnable() { @override public void run() { try { final float newalpha = (.10f * (mlastlightvalue / (mlightsensor.getmaximumrange() / 100))); final objectanimator oa = objectanimator.offloat(mmyappratingbar, "alpha", mmyappratingbarlastalpha, newalpha); oa.addlistener(new animatorlistener() { @override public void onanimationstart(animator animation) { } @override public void onanimationend(animator animation) { try { oa.addlistener(null); oa.addupdatelistener(null); mmyappratingbarlastalpha = newalpha; } catch (exception e1) { // nothing } { try { mtweenlock.release(); } catch (exception e1) { // nothing } } } @override public void onanimationcancel(animator animation) { try { oa.addlistener(null); oa.addupdatelistener(null); mmyappratingbarlastalpha = newalpha; } catch (exception e1) { // nothing } { try { mtweenlock.release(); } catch (exception e1) { // nothing } } } @override public void onanimationrepeat(animator animation) { } }); oa.setinterpolator(new decelerateinterpolator()); oa.setduration(1000); oa.start(); try { if (malphahandler != null) { malphahandler.removecallbacks(runnablealpha); } } catch (exception e1) { // nothing } { malphahandler = null; } } catch(exception e) { try { mtweenlock.release(); } catch (exception e1) { // nothing } } } } // wire handler , runnable if light sensor registered, light event triggered, no current lock(prior light event being handled) public void onsensorchanged(sensorevent event) { if(!mtweenlock.tryacquire()) { return; } try { malphahandler = new handler(); mlastlightvalue = event.values[0]; malphahandler.postdelayed(runnablealpha, 0); } catch(exception e) { malphahandler = null; mtweenlock.release(); } } // when press start button in app, fire light sensor begin work msensormanager = (sensormanager) mcontext.getsystemservice(mcontext.sensor_service); mlightsensor = msensormanager.getdefaultsensor(sensor.type_light); if(mlightsensor == null) { msensormanager = null; return; } msensormanager.unregisterlistener(this, mlightsensor); // clear out prior if existent msensormanager.registerlistener(this, mlightsensor, sensormanager.sensor_delay_ui); // when press stop button in app, force teardown of try { if(malphahandler != null) { malphahandler.removecallbacksandmessages(null); malphahandler = null; runnablealpha = null; } } catch(exception e1) { // nothing }
the issue turned out .onanimationcancel() intermittently being called wherein 'oa' being set null , .onanimationend() being subsequently called after .onanimationcancel() how architecture works. when .onanimationend called, 'oa' @ point null causing npe. since .onanimationend() guaranteed called in both cases, .onanimationcancel() pulled resolving npe.**
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