Run Callback On Main Thread

Question

I have some code that interacts with the Android Facebook SDK, Asynchronously. Unfortunately this means when it returns it is in a background thread.

Cocos-2dx prefers me to interact with it in the Main Thread, especially when doing things like telling the Director to switch scenes (As it involves Open GL)

Is there any way to get some code to run on the Main thread ?

score 54 · Accepted Answer · edited May 23 '17 at 12:34

54

As long as you have a Context, you can do something like this:

Handler mainHandler = new Handler(context.getMainLooper());

And to run code on UI thread:

mainHandler.post(new Runnable() {

    @Override
    public void run() {
        // run code
    }
});

As suggested by kaka:

You could also use the static Looper.getMainLooper() which

Returns the application's main looper, which lives in the main thread of the application.

edited May 23 '17 at 12:34

Community

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1

answered Oct 14 '13 at 18:37

cYrixmorten

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8

You could also use the static [Looper.getMainLooper()](http://developer.android.com/reference/android/os/Looper.html#getMainLooper()) which _"Returns the application's main looper, which lives in the main thread of the application."_. – kaka Apr 07 '14 at 10:42
@kaka Cool, did not know that, it has now been added to the answer :) – cYrixmorten Apr 07 '14 at 10:50
post doesn't exists anymore. – Predrag Manojlovic Jul 02 '16 at 20:22
@PredragManojlovic any reference? According to the documentation it does https://developer.android.com/reference/android/os/Handler.html#post(java.lang.Runnable) – cYrixmorten Jul 04 '16 at 09:04
@cYrixmorten My mistake. There is also Handler in another package so I've made wrong import. Up-voting this. – Predrag Manojlovic Jul 04 '16 at 09:11
@PredragManojlovic alright :) but thanks for the heads up anyways, if it was the case an update of the answer would be required. – cYrixmorten Jul 04 '16 at 09:37
@fnc12 I think it may be easier to have the Java code return control to cocos2d-x on the main thread rather than try to jump onto the main thread in C++ – James Campbell May 22 '17 at 15:35
Perfect answer! – krisDrOid Jul 30 '19 at 21:57

score 12 · Answer 2 · answered Oct 14 '13 at 18:47

12

runOnUiThread(new Runnable() {
    @Override
    public void run() {
        //execute code on main thread
    }
});

answered Oct 14 '13 at 18:47

Lefteris

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Also true but runOnUiThread is only available within Activity and Fragment classes – cYrixmorten Oct 14 '13 at 19:37

score 5 · Answer 3 · answered Jul 31 '15 at 09:22

5

In C++:

Director::getInstance()->getScheduler()->performFunctionInCocosThread([]{
    // execute code on main thread
});

answered Jul 31 '15 at 09:22

Dmytro

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score 3 · Answer 4 · answered Jan 11 '19 at 19:44

You can run code in the main thread in this 2 ways: (with Java 8's lambdas)

If you have an activity instance:

activity.runOnUiThread(() -> {
     // do your work on main thread
});

Otherwise use an Handler object and post a Runnable.

You can use the postDelayed version if you need some delay before executing the code.

 Handler handler = new Handler(Looper.getMainLooper());
 handler.post(() -> {
     // do your work on main thread
 });

Run Callback On Main Thread

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