Android-Getting-Started | Shows how to view and annotate a PDF on Android | Document Editor library

I'm a newbie in android studio and I'm following the tutorial guide androidhive. However I'm stucked at the LoginActivity.java part and the author doesnt feel like want to solve it as well. The thing is that when I compile the code,

Error:(41, 54) error: cannot find symbol variable toolbar

showed up and highlight all the code with R.id, if I delete the toolbar code:

I'm using MotionLayout and am trying to apply a series of transitions (defined in MotionScene file). For example Transition1 changes position of View1, and then Transition2 subsequently changes position of View2. The issue I'm seeing is that Transition2 is causing View1 to revert to it's original layout. I'm triggering the transitions using calls to transitionToState() (I've also tried explicitly providing start/end state for transition using setTransition() and then calling transitionToEnd()).

I saw comment in https://www.raywenderlich.com/8883-motionlayout-tutorial-for-android-getting-started that

if you don’t provide an end constraint for a view, it will disappear. This happens because the library doesn’t know which constraints it should apply at the end of the animation

Is it necessary to also include info on View1 layout in ConstraintSet for Transition2?

There is a "Multi State" example in https://github.com/googlesamples/android-ConstraintLayoutExamples/blob/master/README.md but it looks like transitions included all start from single base state (rather than being "cumulative")

I am trying to convert this RxJava/RxAndroid lesson to RxKotlin/RxAndroid. At the method at Example5 I get error from picture

My getNotesObservable() function is:

I am trying to convert examples from this article from Java to Kotlin. I get error from picture at Exmaple 5:

And I noticed, that without map() function I don't get this error

So, what the point of this error and how to write it right?

I am trying to authenticate login and signup with Firebase. I was following this article on android hive but there was lot of errors, one was this,

import com.google.firebase.auth.FirebaseAuth;

for complete detail version of the code you can follow the above "android hive" link.

I'm having trouble Android Studio to find Adobe Creative SDK.

I have downloaded sample from github.

I have set my Key class as per instruction.

My gradle file of application.

I am integrating MOPUB ADs in application. I am following MOPUB SDK integration steps from https://www.mopub.com/resources/docs/android-sdk-integration/android-getting-started/

After adding mopub-volley-1.1.0.jar, I got following error.

Error:Execution failed for task ':app:transformClassesWithJarMergingForDebug'. com.android.build.api.transform.TransformException: java.util.zip.ZipException: duplicate entry: com/mopub/volley/AuthFailureError.class

My build.gradle code is