I have an Activity, that contains some views and 2 Fragments (for example, TextInputFragment and VoiceInputFragment).
I created the next ViewModels:
ActivityViewModel with void onInput(String value) method
interface InputViewModel with LiveData<String> getInput() method
TextInputViewModel and VoiceInputViewModel as implementation of InputViewModel
Now I want to observe getInput from both fragments and react on them.
I have the next idea:
Activity.onCreate:
ActivityViewModel avm = ViewModelProviders.of(this).get(ActivityViewModel.class);
TextInputViewModel tivm = ViewModelProviders.of(this).get(TextInputViewModel.class);
tivm.getInput().observeForever(avm::onInput);
VoiceInputViewModel vivm = ViewModelProviders.of(this).get(VoiceInputViewModel.class);
vivm.getInput().observeForever(avm::onInput);
Does this idea correct? What happened when configuration change and my ViewModels try to re-observe each other? Is there any solutions?
After reseaching and reading android.arch sources I came to the next solution:
Change type of ActivityViewModel.answer field to MediatorLiveData<String> and add the next method:
public void addAnswerSource(LiveData<String> source) {
answer.removeSource(source); // to prevent throwing "This source was already added with the different observer" exception
answer.addSource(source, s -> answer.setValue(s));
}
Now Activity.onCreate:
ActivityViewModel avm = ViewModelProviders.of(this).get(ActivityViewModel.class);
TextInputViewModel tivm = ViewModelProviders.of(this).get(TextInputViewModel.class);
avm.addAnswerSource(tivm.getInput());
VoiceInputViewModel vivm = ViewModelProviders.of(this).get(VoiceInputViewModel.class);
avm.addAnswerSource(vivm.getInput());
Related
sorry if this is a convoluted question. Working on creating an app for a college course and I'm running into (what appears to be) a race condition in my OnCreate method.
TL;DR - sometimes my spinner populates and I can get an index from it. Sometimes it's not populated yet when trying to get a specific index. Details and code below.
The app is a "course scheduler" for a college student.
I'm creating an Activity that displays existing course information and allows you to edit it. In the OnCreate method for this Activity, I am filling a spinner for "Mentors" for the course and a spinner for which "Term" the course belongs in. This information is being pulled from a Room DB.
I have a seperate activity for a new course and for editing a course. For the "new course" activity, everything works fine. I getAllMentors() or getAllTerms() successfully and fill the spinner list.
For the "Edit Course" Activity, there's an extra step involved and it seems to be causing me some issues.
When editing a course, I pass the intent from the originating Activity with all the necessary EXTRAS. This is successful.
In OnCreate for EditCourseActivity, I do the following:
I get the mentorID from the EXTRA that's passed in from the originating Activity.
I access my MentorViewModel and call my getAllMentors() method which returns LiveData> of all mentors in the db.
because it returns LiveData, I use an observer and loop through the LiveData adding the Name of each mentor to a List and the
entire mentor to a List.
I populate my spinner with the information in List full of mentor names.
then I do a for loop, looping through List looking for one that has the same id as what I grabbed form the EXTRA in step 1.
If I find a match in that list, I call a getMentorName() method to snag their name as a string.
I have a methond getIndex(spinner, string) that will loop through the provided spinner, trying to find a match for the string that's
passed in (mentors name) that I grabbed that should match the ID of
the mentor assigned to the course. This method returns index location
of the matched string in the spinner.
I set the spinner selection to the index found.
I do basically the same process for term.
Me being a new developer, I'm not used to OnCreate running the code synchronously.
Because of this, it appears that I have a race condition somewhere between populating the List of mentor names that populates the spinner, and calling my getIndex() method.
Sometimes the spinner is populated and getIndex works properly and sets the correct mentor. Sometimes the spinner is empty and my getIndex() returns -1 (which it should do in a no-find situation) that populates the spinner with the first item in the list (once it's populated).
protected void onCreate(Bundle savedInstanceState) {
//////////////////////////Handling Mentor spinner menu/////////////////////////////////////////////////
int mentorId = courseData.getIntExtra(EXTRA_COURSE_MENTOR_ID, -1);
final ArrayAdapter<String> sp_CourseMentorAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, mentorNameList);
sp_CourseMentorAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
sp_CourseMentor.setAdapter(sp_CourseMentorAdapter);
final MentorViewModel mentorViewModel = ViewModelProviders.of(this).get(MentorViewModel.class);
//Mentor test = mentorViewModel.getMentorById(mentorId);
mentorViewModel.getAllMentors().observe(this, new Observer<List<Mentor>>() {
#Override
public void onChanged(#Nullable List<Mentor> mentorList) {
if (mentorList != null) {
for (Mentor m : mentorList) {
mentorNameList.add(m.getMentor_name());
mentorListMentor.add(m);
}
}
sp_CourseMentorAdapter.notifyDataSetChanged();
}
});
for(Mentor m: mentorListMentor){
if (m.getMentor_id()==mentorId){
String test = m.getMentor_name();
int spinnerSelectionM2 = getIndexM(sp_CourseMentor, test);
sp_CourseMentor.setSelection(spinnerSelectionM2);
}
}
Is there a way to get them to run asynchronously? Somehow to get the observer doing my getAllMentors() to complete first and populate the spinner, THEN have the for loop run?
Or a better way to handle this?
Thanks in advance.
Room always runs the code on a separated thread, not the Main/UI thread. You can change that behavior with
allowMainThreadQueries()
after initializating your database. This will make the query run first, populate your list and then run your for-loop code. I do not recommend this approach, since it is a bad practice to make queries on the UI thread.
You have two options:
Change your foor loop to a function and call it after adding the values from the observer:
mentorViewModel.getAllMentors().observe(this, new Observer<List<Mentor>>() {
#Override
public void onChanged(#Nullable List<Mentor> mentorList) {
if (mentorList != null) {
for (Mentor m : mentorList) {
mentorNameList.add(m.getMentor_name());
mentorListMentor.add(m);
}
lookForMentor();
}
}
});
private void lookForMentor() {
for(Mentor m: mentorListMentor){
if (m.getMentor_id()==mentorId){
String test = m.getMentor_name();
int spinnerSelectionM2 = getIndexM(sp_CourseMentor, test);
sp_CourseMentor.setSelection(spinnerSelectionM2);
}
}
}
Put the for inside the observer, change the Room DAO to return a List and use LiveData on your own viewmodel:
MentorViewModel.java:
MentorViewModel extends ViewModel {
private MutableLiveData<List<Mentor>> _mentorsLiveData = new MutableLiveData<List<Mentor>>();
public LiveData<List<Mentor>> mentorsLiveData = (LiveData) _mentorsLiveData;
void getAllMentors(){
//room db query
_mentorsLiveData.postValue(mentorsList);
}
}
EditActivity.java:
mentorsViewModel.getAllMentors();
mentorViewModel.mentorsLiveData.observe(this, new Observer<List<Mentor>>() {
#Override
public void onChanged(#Nullable List<Mentor> mentorList) {
mentorsListMentor.addAll(mentorList);
sp_CourseMentorAdapter.notifyDataSetChanged();
for(Mentor m: mentorListMentor){
if (m.getMentor_id()==mentorId){
String test = m.getMentor_name();
int spinnerSelectionM2 = getIndexM(sp_CourseMentor, test);
sp_CourseMentor.setSelection(spinnerSelectionM2);
}
}
}
}
});
I have created a class which extends JavaFX's MenuBar that creates a menu bar for my application.
By default I won't specialized operations, like opening/saving a file and running a simulation, to be disabled (and they are). When a user runs the app they can select an item in the menu File>New>, and based on which component they select it will toggle on the appropriate menu options.
I was planning on doing this by having each component give a list of which items it toggles on, and then activating the appropriate items when the component is created.
However, I cannot access the list of menus from within in a function (am trying to do it with this.getMenus() but from within the function the only function that is recognized it this.getClass()).
Does anyone know why I cannot call getMenus() and how I could get access to it?
Alternatively, if you have a better idea for how I can toggle these menu items, I'd love to hear. I don't think this is a good way to do it, but it is the best idea we have come up with.
private void fileNew()
{
Menu fileNew = new Menu("New");
menuFile.getItems().add(fileNew);
for(String k: CLHM.keySet())
{
CComponent comp = CLHM.get(k);
if(comp.supportedFeatures().contains((new SupportsNew())))
{
MenuItem i = new MenuItem(comp.getName());
fileNew.getItems().add(i);
i.setOnAction(new EventHandler<ActionEvent>()
{
#Override
public void handle(ActionEvent event)
{
CComponent ctemp = CLHM.get(i.getText());
ArrayList<String> menuItems = (ArrayList) ctemp.getMenuItems();
for (String s : menuItems)
{
Scanner scanner = new Scanner(s).useDelimiter("\\s>\\s");
String menu = scanner.next();
//Menu temp = this.getMenus();
/*
Here the program will parse the string of the
Menu path (e.g. File>Open) and activate the
relevant item, if it exists.
*/
}
borderPane.setCenter((Node) ctemp);
}
});
}
}
}
When you use this inside an anonymous class, it actually refers to the anonymous class instance. So in your case, this is an instance of EventHandler, which is why there are so little methods that you can call (because it is an interface type).
What you are looking for is YourExtendedMenuBar.this.getMenus(). This will tell the compiler that you are looking for the enclosing instance. Alternatively, you can simply drop the this keyword (i.e. getMenus()). Doing so will allow you to use/call any accessible members of the anonymous class and its enclosing class.
On the side note, if you replaced that anonymous class with a lambda expression, then this would have meant YourExtendedMenuBar. It is not possible to access any members of the class that the lambda expression represents, at least not directly.
P.S. I have no idea what your toggling is all about, so I can't answer until I figured out what you mean.
This question is not manly for Android, but I will use an android example to explain.
I want to create a class that should override the method onTouchListener, to be used on any object that uses those touch methods.
Since after a touch input, the method starts a function, and since it's a class, it can be instantiate several times (and I want to be instantiate several times), I want to prevent that two instances are called at the same time.
I guess I could create a variable inside the class, that assured that if it's true, it can run the method, but I need to check it for all of the class instances.
And since I want to make this a library, I need to do this inside the class itself.
So my question is,
(Java Question) How can I know that a variable from any instance of a class is true?
(Android Question) Or if this is not possible, How can I prevent multiple touch events at the same time?
You could achieve that with static data and/or method for this class. A static element can be accessible from anywhere using the class name:
ex: MyClass.isAlreadyRunning();
you could for example store in an array all the running status of the instances, and create a static method that checks the array if one is already running.
You can think about making a Singleton Class. Wiki Link
Singleton classes allows to create ONLY one instance/object of that class and then reuse it.
You can use a static field in this context. A static field is identicaly for all instances of an class.
You can do it maybe like this:
public Example implements TouchInterface{
private static boolean actuallyRunning = false;
public void touchExecute(){
if(!actuallyRunning){
actuallyRunning = true;
callYourFunction();
actuallyRunning = false;
}
}
}
You can use singleton class if you want one one instance and if you want to handle the multiple touch events
you can disable as soon as your handler start and enable after that.
you can add a time span in normal practice it is one sec but it depends on you handler's complexity
Like this example:
// Make ur activity class to implement View.OnClickListener
public class MenuPricipalScreen extends Activity implements View.OnClickListener{
#Override
protected void onCreate(Bundle savedInstanceState) {
// setup listeners.
findViewById(R.id.imageView2).setOnClickListener(MenuPricipalScreen.this);
findViewById(R.id.imageView3).setOnClickListener(MenuPricipalScreen.this);
....
}
.
.
.
// variable to track event time
private long mLastClickTime = 0;
//View.OnClickListener.onClick method defination
#Override
public void onClick(View v) {
// Preventing multiple clicks, using threshold of 1 second
if (SystemClock.elapsedRealtime() - mLastClickTime < 1000) {
return;
}
mLastClickTime = SystemClock.elapsedRealtime();
// Handle button clicks
if (v == R.id.imageView2) {
// Do ur stuff.
}
else if (v == R.id.imageView2) {
// Do ur stuff.
}
...
}
.
.`.
You should put "public synchronized" void, so it will prevent to be called in parallel. If you must override, then put a synchronized object in the method so it will do the same.
I essentially have a custom IdlingResource that takes a View a constructor argument. I can't find anywhere that really talks about how to implement it.
I'm trying to use this answer: https://stackoverflow.com/a/32763454/1193321
As you can see, it takes a ViewPager, but when I'm registering the IdlingResource in my test class, I'm not sure how I can get my view.
I've tried findViewById() and I've tried getting the currently running activity and then calling findViewById() on that, with no luck.
Anyone know what to do in this scenario?
Figured it out. To get the view to pass into an idling resource, all you have to do is take the member variable of your ActivityTestRule
For example:
#Rule
public ActivityTestRule<MainActivity> activityTestRule = new ActivityTestRule<>(
MainActivity.class);
and then just call getActivity().findViewById(R.id.viewId)
So the end result is:
activityTestRule.getActivity().findViewById(R.id.viewId);
The accepted answer works as long as a test is running in the same activity. However, if the test navigates to another activity activityTestRule.getActivity() will return the wrong activity (the first one). To address this, one can create a helper method returning an actual activity:
public Activity getCurrentActivity() {
final Activity[] currentActivity = new Activity[1];
InstrumentationRegistry.getInstrumentation().runOnMainSync(new Runnable() {
#Override
public void run() {
Collection<Activity> allActivities = ActivityLifecycleMonitorRegistry.getInstance()
.getActivitiesInStage(Stage.RESUMED);
if (!allActivities.isEmpty()) {
currentActivity[0] = allActivities.iterator().next();
}
}
});
return currentActivity[0];
}
And then it could be used as the following:
Activity currentActivity = getCurrentActivity();
if (currentActivity != null) {
currentActivity.findViewById(R.id.viewId);
}
If you are using ActivityScenarioRule from androidx.test.ext.junit.rules (since ActivityTestRule "will be deprecated and eventually removed from library in the future"), you can get your Activity instance and call findViewById method:
import androidx.test.ext.junit.rules.activityScenarioRule
import androidx.test.ext.junit.runners.AndroidJUnit4
#RunWith(AndroidJUnit4::class) {
#get: Rule
var testRule = activityScenarioRule<MainActivity>()
#Test
fun mainTestCase() {
testRule.scenario.onActivity { activity ->
val view = activity.findViewById<YourView>(R.id.view)
}
}
}
I haven't already used IdilingResources in Espresso, but did you saw these articles:
Espresso: Custom Idling Resource by Chiuki
Wait for it...a deep dive into Espresso's Idling Resources
Also please check official Android Docs: Idling Resources (reference)
To answer your question,
the best way to do it is passing in an instance of one of the Views into the class's constructor. Check: Calling findViewById() from outside an activity
another way is getting view by context. Check android - How to get view from context?
Here's an exmple taken from a link above:
Starting with a context, the root view of the
associated activity can be had by
View rootView = ((Activity)_context).Window.DecorView.FindViewById(Android.Resource.Id.Content);
In Raw Android it'd look something like:
View rootView = ((Activity)mContext).getWindow().getDecorView().findViewById(android.R.id.content)
Then simply call the findViewById on this
View v = rootView.findViewById(R.id.your_view_id);
This might be also useful: How to call getResources() from a class which has no context?
Hope it help
// use case 10b alternate version
// caches a read comment temporarily
public void testCacheReadComment2() throws Throwable{
runTestOnUiThread(new Runnable()
{
#Override
public void run(){
CommentBuilder commentBuilder = new commentBuilder();
Comment comment = commentBuilder.createTopTestComment();
//browse button on main screen
((Button)activity.findViewById(ca.ualberta.cs.team5geotopics.browseButton)).performClick();
//the ListView for the custom adapter
ListView listView = (ListView) activity.findViewById(ca.ualberta.cs.team5geotopics.commentList);
//the custom adapter on the physical screen
ArrayAdapter<Comment> adapter = (ArrayAdapter<Comment>) listView.getAdapter();
adapter.add(comment);
adapter.notifyDataSetChanged();
View view = adapter.getView(adapter.getPosition(comment), null, null);
ViewAsserts.assertOnScreen(listView, view);
//this is the button to view the Top Level comment in the list
ViewAsserts.assertOnScreen(view, (Button) view.viewTopLevelComment);
((Button)view.viewTopLevelComment).performClick();
// is there a way I can get references to the objects
// already instantiated in the test thread?
CacheController cc = activity.getCacheController();
assertTrue(cc.getHistory().contains(comment));
}
});
}
We are using a test driven development style in order to code our project for school. In this test I am trying to prove that after a user views a comment from the list in the adapter, that this comment is cached in a history cache. I'm a little confused about some things and I would like some help, because it would be great if I knew there were no obvious flaws in my test case. these are my questions:
View view = adapter.getView(adapter.getPosition(comment), null, null);
Will this line return the view that is associated with the comment stored in the array adapter? My ArrayAdapter is going to follow a holder patter and I'm not sure if this is the proper way to get access to the buttons I need to mimic the user viewing the comment.
CacheController cc = activity.getCacheController();
I have a CacheController object that is instantiated upon the onCreate() method in our main activity. Now I want to reference this CacheController to see if the history is updated properly. I was just making a new CacheController and mimicking the actions of the CacheController in the test method, but I want to test what happens to my data on the UIthread. So, how do I reference objects in the UI thread?
View view = adapter.getView(adapter.getPosition(comment), null, null);
Will this line return the view that is associated with the comment
stored in the array adapter?
I think it should work, but I don't understand why would you want to access the View.
My ArrayAdapter is going to follow a holder patter and I'm not sure if
this is the proper way to get access to the buttons I need to mimic
the user viewing the comment.
The ArrayAdapter is usually used for a ListView. You should just let ListView handle the click capturing and tell you which element was clicked.
So, how do I reference objects in the UI thread?
You have 2 solutions for this that come to my mind right now:
1) Pass the CacheController instance, for example:
public class YourClass {
private final CacheController cacheController;
public YourClass(final CacheController cacheController) {
this.cacheController = cacheController;
}
public void testCacheReadComment2() throws Throwable {
CacheController cc = this.cacheController;
}
}
2) Singleton: make the CacheController static and put an accessor, for example:
public class CacheController {
private final CacheController instance = new CacheController();
public static CacheController getCacheController() {
return instance;
}
}
In both cases you should be aware about potential multi-threading issues because you're spawning new threads that all share same CacheController instance.