Develop Reference

Timber - Problem with creating a custom Timber Debug Tree class

I'm trying to create a custom Debug Tree class to get the same result as the following:
I have followed this Stackoverflow answer:
Log method name and line number in Timber
But using that answer gives me two problems:
Implementing the custom Debug Tree class does not log anything when I use more than one method.
public class MyDebugTree extends Timber.DebugTree {
#Override
protected String createStackElementTag(StackTraceElement element) {
return String.format("(%s:%s)#%s",
element.getFileName(),
element.getLineNumber(),
element.getMethodName());
}
}
public class BaseApplication extends Application {
#Override
public void onCreate() {
super.onCreate();
if (BuildConfig.DEBUG) {
Timber.plant(new MyDebugTree);
}
}
}
The above causes it to not log at all.
If I use only return element.getFileName(); it successfully logs that one error.
The second problem I'm having is that using a custom DebugTree class does not give me the same results as using err.getStackTrace()[0].getLineNumber().
}, err -> {
Timber.e("Method name: " + err);
Timber.e("Method name: " + err.getStackTrace()[0].getMethodName());
}
The custom Debug Tree class does not display the name of the method I'm trying to log.
Why is it not logging when I use all three methods?
Also how can I get it to log like it would using
err.getStackTrace()[0].getMethodName()?
I'm using 'com.jakewharton.timber:timber:4.7.1'

You seem to be doing it right. I recreated your code in kotlin (programming language should not matter) and i was able to show my logs.
MyDebugTree.kt
class QueenlyDebugTree : Timber.DebugTree() {
override fun createStackElementTag(element: StackTraceElement): String {
return "(${element.fileName}:${element.lineNumber})#${element.methodName}"
}
}
force log using an actual exception:
try {
throw RuntimeException("Hello World")
} catch (e: Exception) {
Timber.e(e)
}
i got a log:
So, from what i saw from your code, its most probably because you have a compact logcat view. To update your logcat view, follow these steps:
1. Make sure you have standard view selected
2. Configure standard view
3. Make sure Show tags is selected and tag column is at max(35)

Method addObserver must be called on the main thread

I started getting this illegal state exception recently.
This is the stack trace:
E/AndroidRuntime: FATAL EXCEPTION: UploaderServiceThread1640451978001
Process: com.sister.ivana4k, PID: 2032
java.lang.IllegalStateException: Method addObserver must be called on the main thread
at androidx.lifecycle.LifecycleRegistry.enforceMainThreadIfNeeded(LifecycleRegistry.java:317)
at androidx.lifecycle.LifecycleRegistry.addObserver(LifecycleRegistry.java:172)
at androidx.activity.ComponentActivity.(ComponentActivity.java:231)
at androidx.fragment.app.FragmentActivity.(FragmentActivity.java:127)
at androidx.appcompat.app.AppCompatActivity.(AppCompatActivity.java:87)
at com.sister.ivana.database.OrmLiteBaseAppCompatActivity.(OrmLiteBaseAppCompatActivity.java:33)
at com.sister.ivana.database.DBServices.VehicleServices.(VehicleServices.java:28)
at com.sister.ivana.upload.UploadType.getFileURL(UploadType.java:548)
at com.sister.ivana.upload.UploadType.createSpinItPicturesUploadDescription(UploadType.java:475)
at com.sister.ivana.upload.UploadType.getUploadRequest(UploadType.java:299)
at com.sister.ivana.upload.Uploader.startCompletionRequest(Uploader.java:704)
at com.sister.ivana.upload.Uploader.processQueue(Uploader.java:443)
at com.sister.ivana.upload.Uploader.handleMessage(Uploader.java:198)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loopOnce(Looper.java:201)
at android.os.Looper.loop(Looper.java:288)
at android.os.HandlerThread.run(HandlerThread.java:67)
I have searched around and found that I could potentially wrap the call to do it on the main thread, unfortunately from what I can see the call is made by an internal library so I am not sure how I could resolve it or at least mitigate it.
What can I do? Let me know if you need more info.
Vehicle Services class:
public class VehicleServices extends OrmLiteBaseAppCompatActivity {
private final String vinNumber;
private final Context context;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
public VehicleServices(String vinNumber, Context context) { //line 28
this.vinNumber = vinNumber;
this.context = context;
}
public Project getProject() {
try {
DatabaseHelper helper = getHelperInternal(this.context);
final Vehicle vehicle = helper.getVehicleDao().queryForId(this.vinNumber);
if (vehicle != null) {
Dao<Project, ?> dao = helper.getProjectDao();
for (Project project : dao) {
final String projectID = project.getProject().replace(",", "");
if (projectID.equals(vehicle.getProject())) {
return project;
}
}
}
} catch (SQLException ex) {
Util.logError("Database error adding new VIN", ex);
}
return null;
}
}
I have to also mention that I inherited this codebase a few days ago and I am aware that best practices were thrown out when building this. (Memory leaks and bugs everywhere, spaghetti code, you name it) I am looking for a way to fix this particular exception to the greatest degree possible.
I have access to all the files except android internal libraries.

Log statement during unit test

I am currently starting to unit test my android application. I am having problems when the unit test exercise code that has log statements in it. Here is a specific case. I have a class called ServiceManager that has a setSystemPause() and a getSystemPause() method. I just want a simple unit test that exercise that logic
ServiceManager class:
public class ServiceManager implements IServiceManager {
private final static String TAG = "ServiceManager";
private boolean mSystemPauseStatus = false;
public boolean getSystemPause () {
Log.i ("TAG", "getSystemPause: " + mSystemPauseStatus);
return mSystemPauseStatus;
}
public void setSystemPause (boolean pauseStatus){
Log.i ("TAG", "setSystemPause: " + pauseStatus);
mSystemPauseStatus = pauseStatus;
}
}
The unit test:
public class ServiceManagerTest {
#Test
public void testSystemPause() throws Exception {
ServiceManager serviceManager = new ServiceManager();
serviceManager.setSystemPause(false);
assert (! serviceManager.getSystemPause());
serviceManager.setSystemPause(true);
assert (serviceManager.getSystemPause());
}
}
The problem are the "Log.i" statements in my code. That causes the following error:
java.lang.RuntimeException: Method i in android.util.Log not mocked.
I understand what is happening, during unit test the android.jar library that is used does not contain the real code and I need to mock that call to "Log.i".
But the code base that I am going to test contains a lot of Log statements. I don't want to mock each usage of the Log facility.
My question is how do people do unit testing in Android while having Log statements in their code. Is there another log facility that I can use in my code instead of the Log class.
I also read the page here:
https://developer.android.com/training/testing/unit-testing/local-unit-tests.html
They suggest doing this in my build.gradle file:
android {
...
testOptions {
unitTests.returnDefaultValues = true
}
}
I don't want to resort to that because I just want the Log to appear. I want to properly mock all other facilities I will use in Android.

But will the Log statement affect the outcome of your unit tests? Problem is that Log is an Android-specific class, and can't be used as part of a JUnit 4 test as it's not part of the Java JDK. If you need Log statements to work as intended, either mock the behaviour out with Mockito, use returnDefaultValues = true, or run the test as a Connected Android Test (/androidTest folder instead of /test).
I personally use returnDefaultValues = true as you mention as Logging is something I'm not usually interested in when Unit Testing, only when I'm trying to track down specific bugs.

You could create a package level method in ServiceManager class which calls Log.i method.
public class ServiceManager implements IServiceManager {
private final static String TAG = "ServiceManager";
private boolean mSystemPauseStatus = false;
public boolean getSystemPause () {
log("TAG", "getSystemPause: " + pauseStmSystemPauseStatusatus);
return mSystemPauseStatus;
}
public void setSystemPause (boolean pauseStatus){
log("TAG", "setSystemPause: " + pauseStatus);
mSystemPauseStatus = pauseStatus;
}
void log(String tag, String message) {
Log.i (tag, message);
}
Then you can override this method in ServiceManagerTest to provide no implementation.
public class ServiceManagerTest {
#Test
public void testSystemPause() throws Exception {
ServiceManager serviceManager = createServiceManager();
serviceManager.setSystemPause(false);
assert (! serviceManager.getSystemPause());
serviceManager.setSystemPause(true);
assert (serviceManager.getSystemPause());
}
private ServiceManager createServiceManager() {
return new ServiceManager() {
#Override
void log(String tag, String message) {
//Do nothing or you could test that this method was called.
}
}
}
}

How to create an Observable in Android?

What I want to do is to create a simple in-memory cache just to try Observables out. However I got stuck because I don't understand how to create an observable. This is the code I have gotten so far:
public class MovieCache {
MovieWrapper movieWrapper;
public Observable<MovieWrapper> getMovies() {
//How to create and return an Observable<MovieWrapper> here?
}
public void setCache(MovieWrapper wrapper) {
movieWrapper = wrapper;
}
public void clearCache() {
movieWrapper = null;
}
}
In the getMovies() method I want to create an Observable and return my local field movieWrapper to the subscriber. How can I do this? I tried with using new Observable.just(movieWrapper) but it results in a null exception.

Take a look at this tutorial as it does exactly what you are looking for. Basically you use defer() to make sure you always get the latest version of your cached object:
public class MovieCache {
MovieWrapper movieWrapper;
public Observable<MovieWrapper> getMovies() {
return Observable.defer(new Func0<Observable<MovieWrapper>>() {
#Override
public Observable<MovieWrapper> call() {
return Observable.just(movieWrapper);
}
});
}
public void setCache(MovieWrapper wrapper) {
movieWrapper = wrapper;
}
public void clearCache() {
movieWrapper = null;
}
}
defer() makes sure that you will get the object upon subscription to the Observable not on creation.
Note however that, according to the author of the post:
The only downside to defer() is that it creates a new Observable each
time you get a subscriber. create() can use the same function for each
subscriber, so it's more efficient. As always, measure performance and
optimize if necessary.

As already said, accepted answer has downside
it creates a new Observable each time you get a subscriber
But it is not the only one.
Consumer won't receive any value if he calls getMovies().subscribe(...) before setCache(...) is called.
Consumer should resubscribe if he want to receive any updates (let's say setCache() can be called multiple times.
Of course all of them can be irrelevant in your scenario. I just want to show you another way (I'm sure there are many more).
You can use BehaviorSubject in order to eliminate all these disadvantages.
public class MovieCache {
private BehaviorSubject<MovieWrapper> mMovieCache = BehaviorSubject.create();
public void setCache(MovieWrapper wrapper) {
mMovieCache.onNext(wrapper);
}
public Observable<MovieWrapper> getMovieObservable() {
//use this if consumer want to receive all updates
return mMovieCache.asObservable();
}
public MovieWrapper getMovie() {
//use this if consumer want to get only current value
//and not interested in updates
return mMovieCache.getValue();
}
public void clearCache() {
//CAUTION consumer should be ready to receive null value
mMovieCache.onNext(null);
//another way is to call mMovieCache.onCompleted();
//in this case consumer should be ready to resubcribe
}
public static class MovieWrapper {}
}
Take a look at BehaviorSubject marble diagram.

RxJava as event bus?

I'm start learning RxJava and I like it so far. I have a fragment that communicate with an activity on button click (to replace the current fragment with a new fragment). Google recommends interface for fragments to communicate up to the activity but it's too verbose, I tried to use broadcast receiver which works generally but it had drawbacks.
Since I'm learning RxJava I wonder if it's a good option to communicate from fragments to activities (or fragment to fragment)?. If so, whats the best way to use RxJava for this type of communication?. Do I need to make event bus like this one and if that's the case should I make a single instance of the bus and use it globally (with subjects)?

Yes and it's pretty amazing after you learn how to do it. Consider the following singleton class:
public class UsernameModel {
private static UsernameModel instance;
private PublishSubject<String> subject = PublishSubject.create();
public static UsernameModel instanceOf() {
if (instance == null) {
instance = new UsernameModel();
}
return instance;
}
/**
* Pass a String down to event listeners.
*/
public void setString(String string) {
subject.onNext(string);
}
/**
* Subscribe to this Observable. On event, do something e.g. replace a fragment
*/
public Observable<String> getStringObservable() {
return subject;
}
}
In your Activity be ready to receive events (e.g. have it in the onCreate):
UsernameModel usernameModel = UsernameModel.instanceOf();
//be sure to unsubscribe somewhere when activity is "dying" e.g. onDestroy
subscription = usernameModel.getStringObservable()
.subscribe(s -> {
// Do on new string event e.g. replace fragment here
}, throwable -> {
// Normally no error will happen here based on this example.
});
In you Fragment pass down the event when it occurs:
UsernameModel.instanceOf().setString("Nick");
Your activity then will do something.
Tip 1: Change the String with any object type you like.
Tip 2: It works also great if you have Dependency injection.
Update:
I wrote a more lengthy article

Currently I think my preferred approach to this question is this to:
1.) Instead of one global bus that handles everything throughout the app (and consequently gets quite unwieldy) use "local" buses for clearly defined purposes and only plug them in where you need them.
For example you might have:
One bus for sending data between your Activitys and your ApiService.
One bus for communicating between several Fragments in an Activity.
One bus that sends the currently selected app theme color to all Activitys so that they can tint all icons accordingly.
2.) Use Dagger (or maybe AndroidAnnotations if you prefer that) to make the wiring-everything-together a bit less painful (and to also avoid lots of static instances). This also makes it easier to, e. g. have a single component that deals only with storing and reading the login status in the SharedPreferences - this component could then also be wired directly to your ApiService to provide the session token for all requests.
3.) Feel free to use Subjects internally but "cast" them to Observable before handing them out to the public by calling return subject.asObservable(). This prevents other classes from pushing values into the Subject where they shouldn't be allowed to.

Define events
public class Trigger {
public Trigger() {
}
public static class Increment {
}
public static class Decrement {
}
public static class Reset {
}
}
Event controller
public class RxTrigger {
private PublishSubject<Object> mRxTrigger = PublishSubject.create();
public RxTrigger() {
// required
}
public void send(Object o) {
mRxTrigger.onNext(o);
}
public Observable<Object> toObservable() {
return mRxTrigger;
}
// check for available events
public boolean hasObservers() {
return mRxTrigger.hasObservers();
}
}
Application.class
public class App extends Application {
private RxTrigger rxTrigger;
public App getApp() {
return (App) getApplicationContext();
}
#Override
public void onCreate() {
super.onCreate();
rxTrigger = new RxTrigger();
}
public RxTrigger reactiveTrigger() {
return rxTrigger;
}
}
Register event listener wherever required
MyApplication mApp = (App) getApplicationContext();
mApp
.reactiveTrigger() // singleton object of trigger
.toObservable()
.subscribeOn(Schedulers.io()) // push to io thread
.observeOn(AndroidSchedulers.mainThread()) // listen calls on main thread
.subscribe(object -> { //receive events here
if (object instanceof Trigger.Increment) {
fabCounter.setText(String.valueOf(Integer.parseInt(fabCounter.getText().toString()) + 1));
} else if (object instanceof Trigger.Decrement) {
if (Integer.parseInt(fabCounter.getText().toString()) != 0)
fabCounter.setText(String.valueOf(Integer.parseInt(fabCounter.getText().toString()) - 1));
} else if (object instanceof Trigger.Reset) {
fabCounter.setText("0");
}
});
Send/Fire event
MyApplication mApp = (App) getApplicationContext();
//increment
mApp
.reactiveTrigger()
.send(new Trigger.Increment());
//decrement
mApp
.reactiveTrigger()
.send(new Trigger.Decrement());
Full implementation for above library with example -> RxTrigger