RxView.clicks crashes app

Question

Trying to do some basic RxJava stuff to lear how it works and was trying to show a progress on button click in a login form (with the RxBindings lib) and then make it disappear after a second. But after the progress is shown and I want to hide it the app crashes. Here's the code I trying to do this with,

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

    mLoginFormView = findViewById(R.id.login_form);
    mProgressView = findViewById(R.id.login_progress);

    RxView.clicks(findViewById(R.id.email_sign_in_button))
            .doOnNext(new Consumer<Object>() {
                @Override
                public void accept(@NonNull Object o) throws Exception {
                    showProgress(true);
                }
            })
            .observeOn(AndroidSchedulers.mainThread())
            .delay(1, TimeUnit.SECONDS)
            .subscribe(new Consumer<Object>() {
                @Override
                public void accept(@NonNull Object o) throws Exception {
                    showProgress(false);
                }
            }, new Consumer<Throwable>() {
                @Override
                public void accept(@NonNull Throwable throwable) throws Exception {
                    Toast.makeText(LoginActivity.this, "Threw: " + throwable, Toast.LENGTH_LONG).show();
                }
            });
}

private void showProgress(final boolean show) {
    int shortAnimTime = getResources().getInteger(android.R.integer.config_shortAnimTime);

    mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
    mLoginFormView.animate().setDuration(shortAnimTime).alpha(
            show ? 0 : 1).setListener(new AnimatorListenerAdapter() {
        @Override
        public void onAnimationEnd(Animator animation) {
            mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
        }
    });

    mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
    mProgressView.animate().setDuration(shortAnimTime).alpha(
            show ? 1 : 0).setListener(new AnimatorListenerAdapter() {
        @Override
        public void onAnimationEnd(Animator animation) {
            mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
        }
    });
}

and the crash I get is,

ComposedException 1 : android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:6357) at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:909) at android.view.ViewGroup.invalidateChild(ViewGroup.java:4690) at android.view.View.invalidateInternal(View.java:11801) at android.view.View.invalidate(View.java:11765) at android.view.View.setFlags(View.java:9704) at android.view.View.setVisibility(View.java:6693) at android.widget.FrameLayout.setVisibility(FrameLayout.java:208) at com.sample.android.rxlogin.ui.LoginActivity.showProgress(LoginActivity.java:60) at com.sample.android.rxlogin.ui.LoginActivity.access$000(LoginActivity.java:19) at com.sample.android.rxlogin.ui.LoginActivity$1.accept(LoginActivity.java:44) at io.reactivex.internal.observers.LambdaObserver.onNext(LambdaObserver.java:59) at io.reactivex.observers.SerializedObserver.onNext(SerializedObserver.java:111) at io.reactivex.internal.operators.observable.ObservableDelay$DelayObserver$1.run(ObservableDelay.java:84) at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:59) at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:51) at java.util.concurrent.FutureTask.run(FutureTask.java:237) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:152) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:265) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) at java.lang.Thread.run(Thread.java:818) Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() at android.os.Handler.(Handler.java:200) at android.os.Handler.(Handler.java:114) at android.widget.Toast$TN.(Toast.java:344) at android.widget.Toast.(Toast.java:100) at android.widget.Toast.makeText(Toast.java:258) at com.sample.android.rxlogin.ui.LoginActivity$2.accept(LoginActivity.java:49) at com.sample.android.rxlogin.ui.LoginActivity$2.accept(LoginActivity.java:46) at io.reactivex.internal.observers.LambdaObserver.onError(LambdaObserver.java:72) at io.reactivex.internal.observers.LambdaObserver.onNext(LambdaObserver.java:62) at io.reactivex.observers.SerializedObserver.onNext(SerializedObserver.java:111) at io.reactivex.internal.operators.observable.ObservableDelay$DelayObserver$1.run(ObservableDelay.java:84) at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:59) at io.reactivex.internal.schedulers.Schedul

I can't understand why this should crash though, since I am using observeOn() with the main Android thread. Could someone please explain what's wrong here? and whats the right way to do this?

Answer 1

Just move your .observeOn(AndroidSchedulers.mainThread()) right after the .delay(1, TimeUnit.SECONDS) block.

Some operators by default don't operate on any particular scheduler, but delay does, as you can se in the documentation it operates in the computation() scheduler (at least the version of the delay that you are using).

Answer 2

You need to use subscribeOn(AndroidSchedulers.mainThread()).

The onClickListener that Rx uses is set on the View during the subscription.