It&#39;s much more semantically correct to use  https://www.googleapis.com/youtube/v3/ as your base URL and then declare `@GET(&quot;search/&quot;)` on your service method.

That said, if you _really_ want your base URL to be the full path you can use `@GET(&quot;.&quot;)` to declare that your final URL is the same as your base URL.

Scala makes a big deal about how what seem to be language features are implemented as library features.

Is there a list of types that are treated specially by the language?

Either in the specification or as an implementation detail?

That would include, for example, optimizing away matches on tuples.

What about special conventions related to pattern matching, for comprehensions, try-catch blocks and other language constructs?

Is String somehow special to the compiler? I see that String enhancement is just a library implicit conversion, and that String concatenation is supported by `Predef`, but is that somehow special-cased by the language?

Similarly, I see questions about `&lt;:&lt;` and `classOf` and `asInstanceOf`, and it&#39;s not clear what is a magical intrinsic. Is there a way to tell the difference, either with a compiler option or by looking at byte code?

I would like to understand if a feature is supported uniformly by implementations such as Scala.JS and Scala-native, or if a feature might actually prove to be implementation-dependent, depending on the library implementation.


What types are special to the Scala compiler?

I&#39;m getting the following messages when launching my app:

    2016-10-12 14:47:23.705002 Discovery[377:147958] [MC] System group container for systemgroup.com.apple.configurationprofiles path is /private/var/containers/Shared/SystemGroup/systemgroup.com.apple.configurationprofiles
    2016-10-12 14:47:23.712212 Discovery[377:147958] [MC] Reading from public effective user settings.

Is &quot;system group container&quot; related to App Groups? I do share data between apps using an App Group and was wondering if this caused this message to be displayed?

I set the data in one app like this:

    var userDefaults = NSUserDefaults(suiteName: &quot;group.com.company.myApp&quot;)
    userDefaults!.setObject(&quot;user12345&quot;, forKey: &quot;userId&quot;)
    userDefaults!.synchronize()

And I retrieve it in another app using something like this:

    var userDefaults = NSUserDefaults(suiteName: &quot;group.com.company.myApp&quot;)
    if let testUserId = userDefaults?.objectForKey(&quot;userId&quot;) as? String {
      print(&quot;User Id: \(testUserId)&quot;)
    }

Did something change in iOS 10 that would cause any problems or cause these messages to show up?



&quot;Reading from public effective user settings&quot; in iOS 10

I am working on Youtube API.
The base URL is `&lt;https://www.googleapis.com/youtube/v3/search/&gt;`

Request :GET

    https://www.googleapis.com/youtube/v3/search?part=snippet&amp;q={search_keyword}&amp;key={API_KEY}

ApiService Interface code-

    public interface ApiService {
        @GET(&quot;&quot;)
        Call&lt;YoutubeResponse&gt; searchVideos(@Query(&quot;part&quot;) String part,
                                       @Query(&quot;q&quot;) String q,@Query(&quot;key&quot;) String apiKey);
    }

The error: **java.lang.IllegalArgumentException: Missing either @GET URL or @Url parameter.**
in the line of code

    Call&lt;YoutubeResponse&gt; call=service.searchVideos(&quot;snippet&quot;,s, URLConstants.Youtube_API_KEY);

I&#39;m a beginner. Please help!

Retrofit error-Missing either @GET URL or @Url parameter

I am working on Youtube API.
The base URL is <code>&#x3C;https://www.googleapis.com/youtube/v3/search/></code>
Request :GET
<pre><code class="hljs language-bash">https://www.googleapis.com/youtube/v3/search?part=snippet&#x26;q={search_keyword}&#x26;key={API_KEY}
</code></pre>
ApiService Interface code-
<pre><code class="hljs language-less">public interface ApiService {
 @GET("")
 Call&#x3C;YoutubeResponse> searchVideos(@Query("part") String part,
 @Query("q") String q,@Query("key") String apiKey);
}
</code></pre>
The error: java.lang.IllegalArgumentException: Missing either @GET URL or @Url parameter.
in the line of code
<pre><code class="hljs language-ini">Call&#x3C;YoutubeResponse> call=service.searchVideos("snippet",s, URLConstants.Youtube_API_KEY);
</code></pre>
I'm a beginner. Please help!

In my application, I need to store lots of images in the device storage. Such files tend to fulfill the device storage, and I want to allow users to be able to choose external SD card as the destination folder. 

I read everywhere that Android doesn&#39;t allow users to write to external SD card, by SD card I mean the external and mountable SD card and **not the external storage**, but file manager applications manage to write to External SD on all Android versions. 

What is the better way to grant read/write access to external SD card on different API levels (Pre-KitKat, KitKat, Lollipop+)?

**Update 1**

I tried Method 1 from Doomknight&#39;s answer, with no avail: 
As you can see I&#39;m checking for permissions at runtime before attempting to write on SD:

    HashSet&lt;String&gt; extDirs = getStorageDirectories();
    for(String dir: extDirs) {
        Log.e(&quot;SD&quot;,dir);
        File f = new File(new File(dir),&quot;TEST.TXT&quot;);
        try {
            if(ActivityCompat.checkSelfPermission(this,Manifest.permission.WRITE_EXTERNAL_STORAGE)==PackageManager.PERMISSION_GRANTED) {
                f.createNewFile();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

But I get an access error, tried on two different devices: HTC10 and Shield K1.

    10-22 14:52:57.329 30280-30280/? E/SD: /mnt/media_rw/F38E-14F8
    10-22 14:52:57.329 30280-30280/? W/System.err: java.io.IOException: open failed: EACCES (Permission denied)
    10-22 14:52:57.329 30280-30280/? W/System.err:     at java.io.File.createNewFile(File.java:939)
    10-22 14:52:57.329 30280-30280/? W/System.err:     at com.myapp.activities.TestActivity.onResume(TestActivity.java:167)
    10-22 14:52:57.329 30280-30280/? W/System.err:     at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1326)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at android.app.Activity.performResume(Activity.java:6338)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3336)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3384)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2574)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at android.app.ActivityThread.access$900(ActivityThread.java:150)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1399)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:102)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at android.os.Looper.loop(Looper.java:168)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:5885)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:819)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:709)
    10-22 14:52:57.330 30280-30280/? W/System.err: Caused by: android.system.ErrnoException: open failed: EACCES (Permission denied)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at libcore.io.Posix.open(Native Method)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at libcore.io.BlockGuardOs.open(BlockGuardOs.java:186)
    10-22 14:52:57.330 30280-30280/? W/System.err:     at java.io.File.createNewFile(File.java:932)
    10-22 14:52:57.330 30280-30280/? W/System.err: 	... 14 more

Universal way to write to external SD card on Android

We&#39;re seeing a few exceptions with the message `Default FirebaseApp is not initialized in this process com.example.app. Make sure to call FirebaseApp.initializeApp(Context) first.` in our Android app in which we just added Firebase Remote Config.

The stack trace is as follows:

    Fatal Exception: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.example.app. Make sure to call FirebaseApp.initializeApp(Context) first.
           at com.google.firebase.FirebaseApp.getInstance(Unknown Source)
           at com.google.firebase.remoteconfig.FirebaseRemoteConfig.getInstance(Unknown Source)
           at com.example.app.fragments.SomeFragment.updateFooter(SourceFile:295)
           at com.example.app.fragments.SomeFragment.onCreateView(SourceFile:205)
           at android.support.v4.app.Fragment.performCreateView(SourceFile:2080)
           at android.support.v4.app.FragmentManagerImpl.moveToState(SourceFile:1108)
           at android.support.v4.app.FragmentManagerImpl.moveToState(SourceFile:1290)
           at android.support.v4.app.BackStackRecord.run(SourceFile:801)
           at android.support.v4.app.FragmentManagerImpl.execSingleAction(SourceFile:1638)
           at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(SourceFile:679)
           at android.support.v4.app.FragmentPagerAdapter.finishUpdate(SourceFile:143)
           at android.support.v4.view.ViewPager.populate(SourceFile:1240)
           at android.support.v4.view.ViewPager.populate(SourceFile:1088)
           at android.support.v4.view.ViewPager.setAdapter(SourceFile:542)
           at com.example.app.SomeActivity.onSomeAsyncCallback(SourceFile:908)
           at com.example.app.SomeDataRetriever.onAsyncHttpCompleted(SourceFile:72)
           at com.example.app.io.AsyncHttp.onPostExecute(SourceFile:141)
           at com.example.app.io.AsyncHttp.onPostExecute(SourceFile:19)
           at android.os.AsyncTask.finish(AsyncTask.java:679)
           at android.os.AsyncTask.access$500(AsyncTask.java:180)
           at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:696)
           at android.os.Handler.dispatchMessage(Handler.java:102)
           at android.os.Looper.loop(Looper.java:150)
           at android.app.ActivityThread.main(ActivityThread.java:5665)
           at java.lang.reflect.Method.invoke(Method.java)
           at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:799)
           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:689)

This is version 9.6.1 and we&#39;re also using other Firebase components:

    compile &#39;com.google.firebase:firebase-ads:9.6.1&#39;
    compile &#39;com.google.firebase:firebase-config:9.6.1&#39;
    compile &#39;com.google.firebase:firebase-invites:9.6.1&#39;
    compile &quot;com.google.firebase:firebase-messaging:9.6.1&quot;

As I can see [from the documentation][1] and [the Javadoc][2] we shouldn&#39;t have to do any manual initialization in our case.

The exception happens on Android 4-6 on a variety of devices.

**Edit:**

I see this question gets a little bit of attention. I think this explanation can be interesting for some of you: https://firebase.googleblog.com/2016/12/how-does-firebase-initialize-on-android.html

  [1]: https://firebase.google.com/docs/remote-config/use-config-android
  [2]: https://developers.google.com/android/reference/com/google/firebase/FirebaseApp

Default FirebaseApp is not initialized

I&#39;m trying to uploading my Android Project on github but I get this error when I try to push:

    Push rejected: Push to origin/master was rejected

I made this steps:

 - VCS-&gt;Import into version control-&gt;Create new repository...
 - From the git bash in Project folder:

    git remote add origin https://github.com/[username]/[project_name].git

 - Git-&gt;Add

 - Git-&gt; Commit directory

 - Git-&gt; Push



Android Studio Git Push Rejected

In the manifest file I added permissions coarse and fine, and when I run on device with Android 6, nothing happens! I try 
everything but no way to get location updates...

What am I doing wrong?

    public class MainActivity extends AppCompatActivity implements LocationListener {
    
        LocationManager locationManager;
        String provider;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    
            provider = locationManager.getBestProvider(new Criteria(), false);
    
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED &amp;&amp; ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                // TODO: Consider calling
                //    ActivityCompat#requestPermissions
                // here to request the missing permissions, and then overriding
                //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
                //                                          int[] grantResults)
                // to handle the case where the user grants the permission. See the documentation
                // for ActivityCompat#requestPermissions for more details.
                return;
            }
            Location location = locationManager.getLastKnownLocation(provider);
    
            if (location != null) {
    
                Log.i(&quot;Location Info&quot;, &quot;Location achieved!&quot;);
    
            } else {
    
                Log.i(&quot;Location Info&quot;, &quot;No location :(&quot;);
    
            }
    
        }
    
    
        @Override
        protected void onResume() {
            super.onResume();
    
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED &amp;&amp; ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                // TODO: Consider calling
                //    ActivityCompat#requestPermissions
                // here to request the missing permissions, and then overriding
                //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
                //                                          int[] grantResults)
                // to handle the case where the user grants the permission. See the documentation
                // for ActivityCompat#requestPermissions for more details.
                return;
            }
            locationManager.requestLocationUpdates(provider, 400, 1, this);
    
        }
    
        @Override
        protected void onPause() {
            super.onPause();
    
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED &amp;&amp; ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                // TODO: Consider calling
                //    ActivityCompat#requestPermissions
                // here to request the missing permissions, and then overriding
                //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
                //                                          int[] grantResults)
                // to handle the case where the user grants the permission. See the documentation
                // for ActivityCompat#requestPermissions for more details.
                return;
            }
            locationManager.removeUpdates(this);
    
        }
    
        @Override
        public void onLocationChanged(Location location) {
    
            Double lat = location.getLatitude();
            Double lng = location.getLongitude();
    
            Log.i(&quot;Location info: Lat&quot;, lat.toString());
            Log.i(&quot;Location info: Lng&quot;, lng.toString());
    
        }
    
        @Override
        public void onStatusChanged(String provider, int status, Bundle extras) {
    
        }
    
        @Override
        public void onProviderEnabled(String provider) {
    
        }
    
        @Override
        public void onProviderDisabled(String provider) {
    
        }
    
        public void getLocation(View view) {
    
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED &amp;&amp; ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                // TODO: Consider calling
                //    ActivityCompat#requestPermissions
                // here to request the missing permissions, and then overriding
                //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
                //                                          int[] grantResults)
                // to handle the case where the user grants the permission. See the documentation
                // for ActivityCompat#requestPermissions for more details.
                return;
            }
            Location location = locationManager.getLastKnownLocation(provider);
    
            onLocationChanged(location);
    
    
        }
    
    }

How to request Location Permission at runtime

I want to prevent the user from going back to the previous screen. So I added code, but this does not work. Are there any solutions for this? The alert pop up is seen but &quot;return false&quot; does not work.

 

    componentDidMount() {
       BackAndroid.addEventListener(&#39;hardwareBackPress&#39;, () =&gt; {
         Alert.alert(&quot;alert&quot;,&quot;alert&quot;)
        
          this.props.navigator.pop();
    
           return false;
       });

Preventing hardware back button android for React Native

I want to get string json from my api using retrofit 2, I have no problem when using retrofit 1 to get this json but using retrofit 2 returns **null** for me.

This is what my json looks like

    {&quot;id&quot;:1,&quot;Username&quot;:&quot;admin&quot;,&quot;Level&quot;:&quot;Administrator&quot;}

This is my API

    @FormUrlEncoded
    @POST(&quot;/api/level&quot;)
    Call&lt;ResponseBody&gt; checkLevel(@Field(&quot;id&quot;) int id);

This is how my code looks like

    Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl(Config.BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
            Api api = retrofit.create(Api.class);
            Call&lt;ResponseBody&gt; call = api.checkLevel(1);
            call.enqueue(new Callback&lt;ResponseBody&gt;() {
                @Override
                public void onResponse(Call&lt;ResponseBody&gt; call, Response&lt;ResponseBody&gt; response) {
                    JsonObject post = new JsonObject().get(response.body().toString()).getAsJsonObject();
                        if (post.get(&quot;Level&quot;).getAsString().contains(&quot;Administrator&quot;)) {
    
                        }
                }
    
                @Override
                public void onFailure(Call&lt;ResponseBody&gt; call, Throwable t) {
                }
            });

I&#39;m new to retrofit 2 and using above code, it always make my apps crash because `response.body().toString()` returns null.

Please guide me on how to get that json string so I can convert it into JsonObject.

Retrofit 2: Get JSON from Response body

I&#39;m trying to use `Retrofit2`, 
I want to add `Token` to my `Header` Like this:

`Authorization: Bearer  Token`
but the `code` below doesn&#39;t work:

    public interface APIService {
        @Headers({&quot;Authorization&quot;, &quot;Bearer &quot;+ token})
        @GET(&quot;api/Profiles/GetProfile?id={id}&quot;)
        Call&lt;UserProfile&gt; getUser(@Path(&quot;id&quot;) String id);
    }

My server is `asp.net webApi`. Please help what should I do?

Retrofit2 Authorization - Global Interceptor for access token

What is the benefit of using Retrofit in combination with Rxjava?

Why is RxJava often used with Retrofit?

I want to call another web-api from my backend on a specific request of user. For example, I want to call **Google FCM** send message api to send a message to a specific user on an event. 

Does **Retrofit** have any method to achieve this? If not, how I can do that?

Call another rest api from my server in Spring-Boot

I&#39;m trying to call an API which requires me to pass in an API key.

My Service call using `HttpURLConnection` is working perfectly.
```java
url = new URL(&quot;https://developers.zomato.com/api/v2.1/search?entity_id=3&amp;entity_type=city&amp;q=&quot; + params[0]);
urlConnection = (HttpURLConnection) url.openConnection();

urlConnection.setRequestProperty(&quot;user-key&quot;,&quot;9900a9720d31dfd5fdb4352700c&quot;);

if (urlConnection.getResponseCode() != 200) {
    Toast.makeText(con, &quot;url connection response not 200 | &quot; + urlConnection.getResponseCode(), Toast.LENGTH_SHORT).show();
    Log.d(&quot;jamian&quot;, &quot;url connection response not 200 | &quot; + urlConnection.getResponseCode());
    throw new RuntimeException(&quot;Failed : HTTP error code : &quot; + urlConnection.getResponseCode());
}
```

However, I&#39;m not sure how this works with `Retrofit` as my call in going into Failure at all times.
Here&#39;s the code I&#39;m using for the same service call

    @GET(&quot;search&quot;)
    Call&lt;String&gt; getRestaurantsBySearch(@Query(&quot;entity_id&quot;) String entity_id, @Query(&quot;entity_type&quot;) String entity_type, @Query(&quot;q&quot;) String query,@Header(&quot;Accept&quot;) String accept, @Header(&quot;user-key&quot;) String userkey);

and I&#39;m using this to call it

    Call&lt;String&gt; call = endpoint.getRestaurantsBySearch(&quot;3&quot;,&quot;city&quot;,&quot;mumbai&quot;,&quot;application/json&quot;,&quot;9900a9720d31dfd5fdb4352700c&quot;);


All these calls are going into the `OnFailure` Method in RetroFit.
If I send it without the HeaderParameters it goes into Success with a 403 because I obviously need to pass the api key somewhere but I cant figure out how.

    @GET(&quot;search&quot;)
    Call&lt;String&gt; getRestaurantsBySearch(@Query(&quot;entity_id&quot;) String entity_id, @Query(&quot;entity_type&quot;) String entity_type, @Query(&quot;q&quot;) String query);



The error I&#39;m getting in OnFailure is 

    java.lang.IllegalStateException: Expected a string but was BEGIN_OBJECT at line 1 column 2 path $

Add Header Parameter in Retrofit

I&#39;m going to send a simple get method to my server(it is Rails app) and get the result using RxJava and Retrofit. The thing that I did is:

My interface:

&lt;!-- language: java --&gt;

    public interface ApiCall {
        String SERVICE_ENDPOINT = &quot;https://198.50.214.15&quot;;
        @GET(&quot;/api/post&quot;)
        io.reactivex.Observable&lt;Post&gt; getPost();
    }

My model is this:

&lt;!-- language: java --&gt;

    public class Post
    {
        @SerializedName(&quot;id&quot;)
        private String id;
        @SerializedName(&quot;body&quot;)
        private String body;
        @SerializedName(&quot;title&quot;)
        private String title;
    
        public String getId ()
        {
            return id;
        }
    
    
        public String getBody ()
        {
            return body;
        }
    
    
        public String getTitle ()
        {
            return title;
        }
    
    }

And this is what I did in my activity:

&lt;!-- language: java --&gt;

    public class Javax extends AppCompatActivity {
        RecyclerView rvListContainer;
        postAdapter postAdapter;
        List&lt;String&gt; messageList=new ArrayList&lt;&gt;();
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_javax);
    
            rvListContainer=(RecyclerView)findViewById(R.id.recyclerView);
            postAdapter=new postAdapter(messageList);
    
            rvListContainer.setAdapter(postAdapter);
        }
        @Override
        protected void onResume() {
            super.onResume();
            Retrofit retrofit=new Retrofit.Builder()
                    .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                    .addConverterFactory(GsonConverterFactory.create())
                    .baseUrl(&quot;https://198.50.214.15&quot;)
                    .build();
            ApiCall apiService=retrofit.create(ApiCall.class);
    
            Observable&lt;Post&gt; observable=apiService.getPost();
    
            observable.subscribeOn(Schedulers.newThread())
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe(responseData -&gt; {
                        messageList.add(responseData.getTitle());
                        postAdapter.notifyDataSetChanged();
                    });
    
        }
    }

I don&#39;t know why I get this error which says I have problem with adapter. I also included the adapter into the gradle:

    E/AndroidRuntime: FATAL EXCEPTION: main
	Process: com.example.hussein.sqlitedatabase, PID: 19445
	java.lang.RuntimeException: Unable to resume activity {com.example.hussein.sqlitedatabase/com.example.hussein.sqlitedatabase.Javax}: java.lang.IllegalArgumentException: Unable to create call adapter for io.reactivex.Observable&lt;com.example.hussein.sqlitedatabase.Post&gt;
		for method ApiCall.getPost
		at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2964)
		at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2993)
		at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395)
		at android.app.ActivityThread.access$800(ActivityThread.java:151)
		at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1321)
		at android.os.Handler.dispatchMessage(Handler.java:110)
		at android.os.Looper.loop(Looper.java:193)
		at android.app.ActivityThread.main(ActivityThread.java:5292)
		at java.lang.reflect.Method.invokeNative(Native Method)
		at java.lang.reflect.Method.invoke(Method.java:515)
		at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
		at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
		at dalvik.system.NativeStart.main(Native Method)
	 Caused by: java.lang.IllegalArgumentException: Unable to create call adapter for io.reactivex.Observable&lt;com.example.hussein.sqlitedatabase.Post&gt;
		for method ApiCall.getPost
		at retrofit2.ServiceMethod$Builder.methodError(ServiceMethod.java:751)
		at retrofit2.ServiceMethod$Builder.createCallAdapter(ServiceMethod.java:236)
		at retrofit2.ServiceMethod$Builder.build(ServiceMethod.java:161)
		at retrofit2.Retrofit.loadServiceMethod(Retrofit.java:169)
		at retrofit2.Retrofit$1.invoke(Retrofit.java:146)
		at $Proxy0.getPost(Native Method)
		at com.example.hussein.sqlitedatabase.Javax.onResume(Javax.java:42)
		at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1197)
		at android.app.Activity.performResume(Activity.java:5343)
		at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2950)
			... 12 more
	 Caused by: java.lang.IllegalArgumentException: Could not locate call adapter for io.reactivex.Observable&lt;com.example.hussein.sqlitedatabase.Post&gt;.
	  Tried:
	   * retrofit2.adapter.rxjava.RxJavaCallAdapterFactory
	   * retrofit2.ExecutorCallAdapterFactory
		at retrofit2.Retrofit.nextCallAdapter(Retrofit.java:240)
		at retrofit2.Retrofit.callAdapter(Retrofit.java:204)
		at retrofit2.ServiceMethod$Builder.createCallAdapter(ServiceMethod.java:234)
			... 20 more

This is my Gradle dependency:

    dependencies {
        compile fileTree(dir: &#39;libs&#39;, include: [&#39;*.jar&#39;])
        androidTestCompile(&#39;com.android.support.test.espresso:espresso-core:2.2.2&#39;, {
            exclude group: &#39;com.android.support&#39;, module: &#39;support-annotations&#39;
        })
        compile &#39;com.android.support.constraint:constraint-layout:1.0.2&#39;
        compile &#39;com.android.support:appcompat-v7:25.3.1&#39;
        testCompile &#39;junit:junit:4.12&#39;
    
        compile &#39;com.squareup.retrofit2:retrofit:2.2.0&#39;
    
        compile &#39;com.android.support:recyclerview-v7:25.3.1&#39;
        compile &#39;com.android.support:design:25.3.1&#39;
    
        compile &#39;io.reactivex.rxjava2:rxandroid:2.0.1&#39;
        compile &#39;io.reactivex.rxjava2:rxjava:2.0.1&#39;
    
        compile &#39;com.jakewharton.retrofit:retrofit2-rxjava2-adapter:1.0.0&#39;
        compile &#39;com.squareup.retrofit2:adapter-rxjava:2.0.2&#39;
    
        compile &#39;com.squareup.retrofit2:converter-gson:2.0.0&#39;
    
        compile &#39;com.google.code.gson:gson:2.4&#39;
    
    }



Unable to create call adapter for io.reactivex.Observable

I am using kotlin coroutines for network request using extension method to call class in retrofit like this

    

    public suspend fun &lt;T : Any&gt; Call&lt;T&gt;.await(): T {

      return suspendCancellableCoroutine { continuation -&gt; 

        enqueue(object : Callback&lt;T&gt; {

            override fun onResponse(call: Call&lt;T&gt;?, response: Response&lt;T?&gt;) {
                if (response.isSuccessful) {
                    val body = response.body()
                    if (body == null) {
                        continuation.resumeWithException(
                                NullPointerException(&quot;Response body is null&quot;)
                        )
                    } else {
                        continuation.resume(body)
                    }
                } else {
                    continuation.resumeWithException(HttpException(response))
                }
            }

            override fun onFailure(call: Call&lt;T&gt;, t: Throwable) {
                // Don&#39;t bother with resuming the continuation if it is already cancelled.
                if (continuation.isCancelled) return
                continuation.resumeWithException(t)
            }
        })

          registerOnCompletion(continuation)
      }
    }


then from calling side i am using above method like this 

    private fun getArticles()  = launch(UI) {

        loading.value = true
        try {
            val networkResult = api.getArticle().await()
            articles.value =  networkResult

        }catch (e: Throwable){
            e.printStackTrace()
            message.value = e.message

        }finally {
            loading.value = false
        }

    }

i  want to exponential retry this api call in some case i.e (IOException) how can i achieve it ??


How to Exponential Backoff retry on kotlin coroutines

I am trying to consume an API using Retrofit and Jackson to deserialize. I am getting the onFailure error `No Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator`.

Content Type	Original Author	Original Content on Stackoverflow
Question	ankushbbbr	View Question on Stackoverflow
Solution 1 - Android	Jake Wharton	View Answer on Stackoverflow

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