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Passing Objects Between Intents (intent.putExtra), with Realm Objects

I have realm objects with Primary keys here's an example:
#RealmClass
public class Person extends RealmObject(){
#PrimaryKey
Int personID;
String name;
Int age;
}
The Person onjects are viewed in a recycler view, where the viewholder has an OnClick method. The OnClick method is fully functional, in the sense that screens change and everything inside it executes. However the Data from the specific Person object selected does not pass through.
Here is the code inside the OnClick method:
Intent intent = new Intent(this, PersonStats.class);
intent.putExtra("I don't know what to put here!");
startActivity(intent);
Where PersonStats is the class that will show all the stats of the Person object selected from the recycler view. I've been messing around with the intent.putExtra function but I can't get it to work. How would I go about this?
Edit: I'm asking for how to get the specific Realm Object that I selected from the recycler view so I can pass it through putExtra. As RecyclerView postion != PrimaryKey.

How to get a view from within Espresso to pass into an IdlingResource?

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

Android remove and add to ArrayList in between activities

I'm making my first android app and here's where i'm stuck.
I have an activity A which requires 4 players to be picked.
I'm passing to the activity PickPlayer 1,2,3,4 according to which player i want to fill.
ImageButton addp1 = (ImageButton)findViewById(R.id.player1);
addp1.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v)
{
Intent i = new Intent(getApplicationContext(), PickPlayer.class);
i.putExtra("playersList", playersList);
startActivityForResult(i, 1);
}
});
On the PickPlayer activity i have a list which is populated and each item receives a listener.
final ArrayList<Player> playersList = (ArrayList<Player>)getIntent().getSerializableExtra("playersList");
lv.setAdapter(new PlayerItemAdapter(this, android.R.layout.simple_list_item_1, playersList));
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapter, View view, int position, long arg) {
player = playersList.get(position);
playersList.remove(position);
Intent intentMessage = new Intent();
intentMessage.putExtra("player", player);
intentMessage.putExtra("playersList", playersList);
setResult(RESULT_OK, intentMessage);
finish();
}
});`
The above works fine by creating the playersList on activity A and passing it through from one to another each time and removing the player from the playerList on click.
Problem is if a player is chosen by mistake he needs to be put back into the list again once replaced by someone else.
Any suggestions on implementing this ?
One way i thought of is to pass from activity A to PickPlayer the player ( if one is assigned already at his position ) and readding him to the playerList again but i'm sure there's a better way for it.
I'm new to android so i have no idea about resources and best practises.
( example passing an object through activities or an id and run a db query).
Thanks

IMO, you'll achieve best results with a singleton class (or methods on Application instance - here a good stackoverflow question about it).
Your array would be an internal member of the singleton and have an boolean attribute to indicate if a player is already picked or not. Some methods using this attribute can be implemented like:
List<Player> getPickedPlayers()
List<Player> getNotPickedPlayers()
void setPlayerPicked(Player player)
void setPlayerNotPicked(Player player)
and so on...
Hope it helps!

When you send object through an Intent's bundle (i.putExtra("playersList", playersList);), it is marshalled and then unmarshalled on the other side (the new activity). This mean you have 2 instances of ArrayList and its content (one in each activity). If you wish to share data between activity A and activity B, I suggest you store it on an Application instance or by using a singleton.
If your data is coming from a database, you can pass the id through the intent, and get the list of players and the special player with a database query.

Not sure if this is the best way to accomplish this but i'm going to share with you.
I move the arrayList with the players back and forth in between the activities.
Once the player is sent back it's removed from it and kept in an object player1,player2,player3 etc etc.
So if the user clicks the button that has already a player assigned to it i simply add that player again into the list and pass the arrayList as i would do if it was empty.

JUnit test on android app with cache and ArrayAdapter

// 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.

How to get current content view in Android programming?

I know that I can set the content of the view in an Android app by saying setContentView(int). Is there a function I can use to know what the current content view is? I don't know if that makes any sense, but what I'm looking for is a function called, say, getContentView that returns an int.
Ideally, it would look like this:
setContentView(R.layout.main); // sets the content view to main.xml
int contentView = getContentView(); // does this function exist?
How would I do that?

Citing Any easy, generic way in Android to get the root View of a layout?
This answer and comments give one method: [Get root view from current activity
findViewById(android.R.id.content)
Given any view in your hierarchy you can also call:
view.getRootView()
to obtain the root view of that hierarchy.
The "decor view" can also be obtained via getWindow().getDecorView(). This is the root of the view hierarchy and the point where it attaches to the window, but I'm not sure you want to be messing with it directly.

You can do making a setter and getter of current view by id only
private int currentViewId = -1;
public void setCurrentViewById(int id)
{
setContentView(id);
currentViewId = id;
}
public int getCurrentViewById()
{
return currentViewId;
}
And then in
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setCurrentViewById(R.layout.main_layout);
}
Hope this helps.

In an Activity, you can do
View rootView = null;
View currentFocus = getWindow().getCurrentFocus();
if (currentFocus != null)
rootView = currentFocus.getRootView();
As described above, there is also
View decorView = getWindow().getDecorView();
as well as
View decorView = getWindow().peekDecorView();
The difference between the latter two is that peekDecorView() may return null if the decor view has not been created yet, whereas getDecorView() will create a new decor view if none exists (yet). The first example may also return null if no view currently has focus.
I haven't tried out whether the root view and the decor view are the same instance. Based on the documentation, though, I would assume they are, and it could be easily verified with a few lines of code.

if you have two content views then you can put a tag inside the relative layout of each one. and then get the view by tag name. if tag name is the one desire then blablabla. Hope this help for whoever is searching for a solution.