java - Does wait() need synchronization on local variable -


i had code (which working fine):

public static void runonuithread(activity c, final runnable action) {     // check if on ui thread     if (looper.getmainlooper() == looper.mylooper()) {         // if are, execute         action.run();         return;     } // else run runnable on ui thread , wait     runnable r = new runnable() {         @override         public void run() {             action.run();             synchronized (this) {                 this.notify();             }         }     };     synchronized (r) {         try {             c.runonuithread(r);             r.wait();         } catch (interruptedexception e) {             e.printstacktrace();         }     } }

and getting synchronization on local variable warning. suggested, removed synchronization on local variable, in order fix warning:

public static void runonuithread(activity c, final runnable action) {     // check if on ui thread     if (looper.getmainlooper() == looper.mylooper()) {         // if are, execute         action.run();         return;     } // else run runnable on ui thread , wait     runnable r = new runnable() {         @override         public void run() {             action.run();             this.notify();         }     }     try {         c.runonuithread(r);         r.wait();     } catch (interruptedexception e) {         e.printstacktrace();     } }

and getting exception when calling method:

06-15 09:18:13.252 27282 27282 e   androidruntime                               fatal exception: main 06-15 09:18:13.252 27282 27282 e   androidruntime                               java.lang.illegalmonitorstateexception: object not locked thread before notify() 06-15 09:18:13.252 27282 27282 e   androidruntime                               @ java.lang.object.notify(native method) 06-15 09:18:13.252 27282 27282 e   androidruntime                               @ org.matapps.android.simpleappcreator.utils$100000007.run(utils.java:673) 06-15 09:18:13.252 27282 27282 e   androidruntime                               @ android.os.handler.handlecallback(handler.java:615) 06-15 09:18:13.252 27282 27282 e   androidruntime                               @ android.os.handler.dispatchmessage(handler.java:92) 06-15 09:18:13.252 27282 27282 e   androidruntime                               @ android.os.looper.loop(looper.java:137) 06-15 09:18:13.252 27282 27282 e   androidruntime                               @ android.app.activitythread.main(activitythread.java:4867) 06-15 09:18:13.252 27282 27282 e   androidruntime                               @ java.lang.reflect.method.invokenative(native method) 06-15 09:18:13.252 27282 27282 e   androidruntime                               @ java.lang.reflect.method.invoke(method.java:511) 06-15 09:18:13.252 27282 27282 e   androidruntime                               @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:1007) 06-15 09:18:13.252 27282 27282 e   androidruntime                               @ com.android.internal.os.zygoteinit.main(zygoteinit.java:774)

i'm pretty sure need synchronization (as runnable runs on different thread), told local variables shouldn't have synchronization. tips? thanks!

i don't know android development tools, warning sounds over-zealous. compiler trying avoid synchronizing on instance visible single thread. it's smart enough know local variable, r, can seen 1 thread, apparently not smart enough know r in original thread , this in new thread both refer same instance.

i try work around problem making r instance variable.


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