Recursively Chaining ConstraintLayout Transitions with Runnable stops after first run

Question

I am attempting to create a toggling animation for a custom menu. There are multiple menus that can be chosen by different buttons. When no menu is open, tapping on a button should open that menu. If another menu is open, the open one is closed and after that animation, the chosen one should be opened. every closing/opening action is coupled with a ConstraintLayout transition.

As it didn't work properly, I created the following test procedure:

@Override
protected void onCreate(Bundle savedInstanceState) {
    ...
    ConstraintLayout layout_main;
    ConstraintSet l_mh0c = new ConstraintSet();
    ConstraintSet l_mh1o = new ConstraintSet();
    ConstraintSet l_mh1c = new ConstraintSet();

    Button btn;
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            toggleOne();
        }
    });
    layout_main = (ConstraintLayout) findViewById(R.id.constraintMain);
    l_mh1o.clone(this, R.layout.main_menue_header1_open);
    l_mh1c.clone(this, R.layout.main_menue_header1_closed);
    l_mh0c.clone(this, R.layout.activity_main);
    ...
}

int openedMenue = -1;
long animationTime = 1000;
private void toggleOne() {
    TransitionManager.endTransitions(layout_main); //<- makes no difference when commented
    if(openedMenue==1) {              
        System.out.println("sync closing");
        Runnable r = () -> toggleOne();
        closeMenue(1, animationTime, r);
    } else {
        System.out.println("sync opening");
        startMenue(1, animationTime);
    }
}

public void startMenue(Integer index, final Long maxtime) {
    Transition t;
    switch (index) {
        case 1:
            t = new ChangeBounds();
            t.setDuration(0).addListener(new TransitionEndListener() {
                @Override
                public void onTransitionEnd(Transition transition) {
                    Transition t = new ChangeBounds();
                    t.setDuration(maxtime / 2).addListener(new TransitionEndListener() {
                        @Override
                        public void onTransitionEnd(Transition transition) {
                            Transition t = new ChangeBounds();
                            t.setDuration(maxtime / 2);
                            TransitionManager.beginDelayedTransition(layout_main, t);
                            l_mh0o.applyTo(layout_main);
                            openedMenue = 1;
                            System.out.println("sync start finished");
                        }
                    });
                    TransitionManager.beginDelayedTransition(layout_main, t);
                    l_mh1o.applyTo(layout_main);

                }
            });
            TransitionManager.beginDelayedTransition(layout_main, t);
            l_mh1c.applyTo(layout_main);
            // the following does not provoke any changes
            Scene s = new Scene(layout_main); 
            TransitionManager.go(s);
            break;
    }
}

private void closeMenue(int index, final long maxtime, Runnable callback) {
    System.out.println("sync closing menue " + openedMenue);
    Transition t;
    switch (index) {
        case 1:
            t = new ChangeBounds();
            t.setDuration(maxtime/2).addListener(new TransitionEndListener() {
                @Override
                public void onTransitionEnd(Transition transition) {
                    Transition t = new ChangeBounds();
                    t.setDuration(maxtime/2).addListener(new TransitionEndListener() {
                        @Override
                        public void onTransitionEnd(Transition transition) {
                            Transition t = new ChangeBounds();
                            t.setDuration(0);
                            TransitionManager.beginDelayedTransition(layout_main, t);
                            l_mh0c.applyTo(layout_main);
                            openedMenue = -1;
                            try {
                                callback.run();
                            } catch (Exception e) { e.printStackTrace(); }
                        }
                    });
                    TransitionManager.beginDelayedTransition(layout_main, t);
                    l_mh1c.applyTo(layout_main);
                    openedMenue = 1;
                }
            });
            TransitionManager.beginDelayedTransition(layout_main, t);
            l_mh1o.applyTo(layout_main);
            break;
    }
}

When I run it, I get the following output:

[Button Click]
sync opening
sync start finished
[Button Click]
sync closing
sync closing menue 1
sync opening
sync start finished // problem

However, the last line is never printed; It seems as if (after the closing action starts the opening action again) the first transition in startMenue() never does a callback to the onTransitionEnd().

Here is the TransitionEndListener (just a simple wrapper for the interface)

public abstract class TransitionEndListener implements Transition.TransitionListener {

    @Override
    public final void onTransitionStart(Transition transition) {}

    @Override
    public final void onTransitionCancel(Transition transition) {}

    @Override
    public final void onTransitionPause(Transition transition) {}

    @Override
    public final void onTransitionResume(Transition transition) {}
}

I already checked if the second starting Transition is cancelled by putting a print statement in the onTransitionCancel() which doesn't seem to be the case.

Can you please explain why this is happening?

UPDATE

I found this post on TransitionManager callbacks;

The Transition from mh0c t0 mh1c is a ConstraintLayout transition, because the constraints actually change; however, the transition is not visible on the UI because the width of the element in transition is 0. (This transition is a jump from one menu point to the other that should not be visible.)

Could this be a reason that the Transition does not do the callback?

And if so; how can I get around this?

UPDATE 2 I was reading the documentation and may have found a solution using TransitionManager.go(scene, transition).

--> Unfortunately this did not work; see code of startMenue() for changes

Answer 1

After more and more struggling and reviewing these posts:

• Animate visibility of a view from gone to visible with animation
• TransitionListener callbacks not called when there is nothing to change
• Why does my Android transition ignore the TransitionListener?

I have found out what caused the trouble:

In the most inner part (the most inner callback) of closeMenue()

Transition t = new ChangeBounds();
t.setDuration(0);
TransitionManager.beginDelayedTransition(layout_main, t);
l_mh0c.applyTo(layout_main);
openedMenue = -1;
try {
     callback.run();
} catch (Exception e) { e.printStackTrace(); }

The sequence of commands is slightly wrong. It should look like this:

Transition t = new ChangeBounds();
t.setDuration(0).addListener(new TransitionEndListener() {
    @Override
    public void onTransitionEnd(Transition transition) {
        try {
            callback.run();
        } catch (Exception e) { e.prtinStackTrace(); }
    }
});
TransitionManager.beginDelayedTransition(layout_main, t);
l_mh0c.applyTo(layout_main);
openedMenue = -1;

This makes sure to first finish the closing transition and THEN starting the opening transition.