title: Observable.fromCallable() does not Return data from Arraylist in Android using RXJava
body: <p>I am trying to use RXjava to get data from an Arraylist in Android</p>
  <pre><code>public ArrayList&lt;String&gt; SelecIDValueGetterObservable(Context mContext) {
          ArrayList&lt;String&gt; SelectedIds = new ArrayList&lt;&gt;();
          CompositeDisposable mCompositeDisposable = new CompositeDisposable();
          mCompositeDisposable.add(Observable.fromCallable(() -&gt; SelecetIDValuegetter(mContext))
                  .subscribeOn(Schedulers.io())
                 // .observeOn(AndroidSchedulers.mainThread())
                  .subscribeWith(new DisposableObserver&lt;ArrayList&lt;String&gt;&gt;() {
                      @Override
                      public void onNext(ArrayList&lt;String&gt; IdObsList) {
                          Toast.makeText(mContext,
                                  &quot;size &quot; + IdObsList.size(), Toast.LENGTH_LONG).show();
                          
                              for (int i = 0; i &lt; IdObsList.size(); i++) {
                                  SelectedIds.add(IdObsList.get(i));
                              }
                        
                      }
  
                      @Override
                      public void onError(Throwable e) {
                          FirebaseCrashlytics.getInstance().recordException(e);
                      }
  
                      @Override
                      public void onComplete() {
                          // mCompositeDisposable.dispose();
                      }
                  })
          );
          return SelectedIds;
      }
  </code></pre>
  <p>the <code>SelecetIDValuegetter(mContext)</code> is Like this</p>
  <pre><code>    public ArrayList&lt;String&gt; SelecetIDValuegetter(Context mContext) {
              ArrayList&lt;String&gt; SelectedIds = new ArrayList&lt;&gt;();
               SelectedIds .add(&quot;A&quot;);
               SelectedIds .add(&quot;B&quot;);
               SelectedIds .add(&quot;C&quot;);
              SelectedIds .add(&quot;D&quot;);
              return SelectedIds ;
          }
  </code></pre>
  <p>If   SelecetIDValuegetter emits data normally, hwoever It deosnot work In Rxjava, how can we do it</p>