I was in the midsts of tinkering in android with the goal of trying to make this small exploration game. I actually got pretty far so far: a nice sprite system, a title screen with a main menu that is all in game code (no UI buttons or anything) that launch various activities. An activity that loads this cool map view, that when clicked on will load up another view of a more detailed "zoomed in" action part of a map. It all works pretty well but now I am left wondering how well I am going about this.
(What happens to a view when you instantiate and then move the set the context to a new view? I am guessing as long as the activity is alive all the instantiations of various views that an activity uses are still good? And in an activities onPause is when id have to save the data thats changed in these views to persist the state in the event the user quits the game etc.. ?)
I have three menu options at the start of the game. The main one is:
New Game
The new game, I launch my main map
activity that can launch three views:
First two are a loading screen for
the second, a map screen.
Third view is a more detailed action
orientated part that uses this sprite
engine I developed.
It all works pretty good as in the map view you click on a cell it tells the Calling Activity through a listener to start the detailed action view, and passes in the ID of the cell (so it knows what objects to load in the detailed view based on the cell clicked in second view). (This took me awhile to figure out but someone helped here on another question to get this.) Reference that helped me on this part here. I also used the various information here on ViewSwitcher.
I got even a yes no dialog box in the second view that asks if they really wanna goto that cell when they click on it, a yes tells the calling activity to set the new view. What helped me to get this working was this reference here. I also had to fiddle with the calls to getContext and that, I am still not 100% sure what getResources and getContext do for me.
So is it bad practice to call and load a dialog from a view? If it is, then I don't understand how if I have an event in the view that needs to pop up a dialog how I do that? Call back to the activity and let the activity handle it the dialog response and then call a method on the view for the response?
So far all this works great, I did have a bit to learn about threads too. I spawn a different thread for my MenuView (handles the detection of button clicks and responses), my CellMap view which handles the cool big map that users can click on to see the indepth view which is my SystemView view.
So basically the activity call list is like this:
Home.Activity -> ScrollMap.activity which listens to CellMap wher ethe Yes/No dialog apperas (in the view of CellMap) and if the answer is yes to the question, then the onTouchEvent starts up the SystemView view using
private CellMap.MapClickedListener onTouchEvent=
new CellMap.MapClickedListener() {
#Override
public void onMapClick(int id) {
setContentView(new SolarSystem(theContext,id));
}
};
To help anyone else, that listener had to be defined in my CellMap class. Then in the ScrollMap activity when I am about to start the CellMap I just call a method to CellMap sets the map click listener. So far this is the only way I have been able to get data from a dialog (in this case a it was clicked so set the new view) back to the calling activity. Is this proper practice?
Now my biggest question is, I have a playerObject class I want to initialize on new game event (I know how to detect that push) and that then is available to any view in any activity for the life time of the cycle. So far the game activity has just two (3 if you count the loading progress bar) views. I want to get the players name, is that another activity or view? I cannot find a decent tutorial of just how to make a simple input dialogg box that would return a string.
How do i go about passing this stuff around? After I get the players name from wherever that edit box is to be loaded, I want to set the players name in the class and pass that class instance off to another view or activity so they may get at that data. Everything I have searched on this seemed like overkill or not the right way. Whats the best way to pass this "playerClass" around so that I can access it from other views (to say display the players name in every view).
I also have my Home Activity that waits for an onClick on 3 buttons, it then launches their activity that shows the view. I realize a continue game and new game are the same activity and will just change in data loaded off the drive to restore a save game. When the new game button is clicked I would love to get the players name they want to use and of course set the member of the playerClass to this name so it persists.
Where do I call (an edit dialog is it?) the edit dialog from? (more over how do I build one that can take an okay button and input from keyboard etc). Id also like to make it pretty, maybe I could have a simple view that has one edit box in it and a nice image background (though I haven't figured out how to place the edit boxes to fit nicely matching a background i draw for it. I guess id like an edit dialog I can skin to look how i want it to and fit the look of the game).
I am actually kinda happy what I got so far its looking not to bad, just not sure about some specifics like getting user input for a name of the player. Storing that information and passing it then to other activities and views.
Is it better to have one GameMain activity, and a ton of views:
Map view
Character sheet view
inventory view etc etc?
Or Should there be diff activities in there somewhere as well?
You've written a lot here, so I'm go gonna go ahead and answer the questions I think you're asking.
First, how can one share information between activities and views? If you're just sharing it between views in a single activity, store it in the instance of the Activity subclass.
Sharing between activities requires a little bit more. Instead of using an instance of the default Application class, you can create a subclass of Application and use that instead. Put your data in fields of that subclass. To tell your app to use your subclass, modify the app manifest like so:
<application
....
android:name=".YourAppClassNameHere">
....
</application>
As for getting user input, the simple answer is use the built-in EditText view. since you seem to want to give your game a more "custom" style, though, you may need to go about creating your own editable textbox. That and buttons should allow for most sorts of basic user input.
Now, good practice vis-a-vis activities and views. I'm not aware of a standard for this, but when designing I generally try to think of activities as more conceptually separate elements, whereas views are conceptually interwoven. the line between the two is dependent, in part, on the scope of the app; an app with a narrow focus can afford to break more actions down into different activities than can one with a much broader focus.
Your "GameMain" example is a bit on the fence, but I think you've made the right choice: the activity is "playing the game," as opposed to a menu or high-scores table, and the views present different aspects of the game being played.
Related
I've spent 8 years programming and for 8 years I've been pretty happy, but after using Android Studio for two weeks I already want to
So here's the deal. I made 2 layouts. One is the default, named activity_main.xml, the other is named graph_layout.xml. They are both ConstraintLayouts (but the same issue occurred when I tried making graph_layout a LinearLayout or RelativeLayout, so we can rule that out as a factor).
In activity_main, there's a button with the ID, graph_button_1. When I click it, it prints to the console "AAAAAAAAAAAAAAAAAAAA" (but with more A's) and switches from activity_main layout to graph_layout. As it should, that's precisely what I designed it to do.
Now, here's the problem. I also have a button in graph_layout with the ID, calc_button_3. When I click this button, it's supposed to print to the console "AAAAAAAAAAAAAAAAAAAAA2" (but with more A's) and then switch from graph_layout to activity_main. It doesn't do that, though. It prints to the console a little message that, "yes, you did click the button, here are all the details of how you clicked that button" (I'm paraphrasing), but it does not print "AAAAAAAAAAAAAAAAAAAAAAA2" to the console, nor does it switch back to activity_main. (If you're wondering, the AAAAA message is just to see whether the setOnClickListener functions are actually executing).
Speaking of which, here's what the setOnClickListener does for calc_button_3:
//final Context context = this;
calcButton3.setOnClickListener(new View.OnClickListener() { //I know I can use lambda funcitons, but I wanted to play it safe
#Override
public void onClick(View v) {
//Intent intent = new Intent(context, MainActivity.class); //This was one of the solutions I found online. It does not do anything.
//startActivity(intent);
System.out.println("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA2");
setContentView(R.layout.activity_main);
}
});
To be fair, I'm a step in the right direction. Before, this function made my app crash. Now, it just does nothing. So...that's a little better, and I'd like to thank the LayoutInflater class for making that possible. I'd also like to point out that I'm willing to supply you with any code or extra information you might want to see. I'd send the whole MainActivity.java file if I could, but I know from experience the longer I make my question, the less likely people are to answer, and it is a VERY long file.
I've scoured the internet for a solution to this, and while I've found people with a similar problem, none of their solutions worked for me.
Your help is greatly appreciated. Thank you.
Below, I will attach any code or additional info anyone in the comments asks me to give them:
You have to start a new activity using intent or if you want to use the same activity then use fragments. and replace fragment layout on button press. but you can not directly use setContentView();
All setContentView(R.layout.activity_main) does is inflate that layout file into its hierarchy of View objects, and display that in the current Activity. You're still in the same Activity, you've just changed its contents.
When you say you're doing this:
In activity_main, there's a button with the ID, graph_button_1. When I click it, it prints to the console "AAAAAAAAAAAAAAAAAAAA" (but with more A's) and switches from activity_main layout to graph_layout.
does that mean you're "switching" by calling setContentView there too, instead of starting a different Activity that displays graph_layout?
If so, and all your code for both layouts is in the same Activity, then your problem is probably related to the fact you're replacing your Views with a new set of objects when you call setContentView. If you set up your buttons like this:
// a Button from your current view hierarchy gets assigned to this at some point
val someButton: Button
// just use the lambda, it's literally the same as creating the object under the hood
someButton.setOnClickListener {
// do a thing
}
And then later you call setContentView(R.layout.some_layout), then whatever Button object someButton is referencing is no longer on the screen. So you can't see it, you can't click it. If you just inflated the same layout as before (creating an entirely seperate set of View objects) then there's another button in the same place - but you haven't set a click listener on it, so it doesn't do anything.
So if you are going to go replacing the view hierarchy like this, then you need to perform your View setup (like assigning click listeners) when you create those new views. If you just set things up when the Activity starts, then it's only applied to the view hierarchy in use at that moment. As soon as you replace it with setContentView, that stuff is gone.
So you could write functions that "switch" to one layout or the other by calling setContentView and then applying the click listeners. Generally speaking though, this isn't how you normally do things in Android. The old way would be to create separate Activities for each screen, a more modern approach is using Fragments which can be swapped out manually or by using something like the Navigation library.
Either way, both those approaches involve configuring your Activity or Fragment once during setup, making buttons do this or that, and then you're done. Everything's neatly separated and self-contained, instead of you having to swap views out and rewire everything according to the state you want to display. That's just complicating things, and it'll get much worse if you start adding more screens you have to juggle!
I'd recommend at least taking a look at the Fragments guide, or the Navigation component if you have time. The latter has more to learn, but it also handles a lot of complexity for you. It would help to at least have an understanding of the usual way of doing things, anyway!
New to Android. Trying to understand the technical downside of a design.
I have an ItemSelectorView which has both an availableItems collection as well as a selectedItem property. The latter is displayed at runtime along with a chevron letting the user know they can change it.
Functionality-wise, it's similar to a spinner except rather than showing a pop-up with the choices, it launches a second activity called ItemSelectorActivity which shows all of the available items from the ItemSelectorView which launched it, as well as helpful information about what each option means as well as the ability to search and filter.
When a user selects one, their choice is then returned back to the originating ItemSelectorView via a trip through MainActivity's onActivityResult override. The override then figures out which ItemSelectorView it's responding to and forwards it along.
However, I really didn't like the way MainActivity had to insert itself into the process just to get the result from ItemSelectorActivity. Plus, if ItemSelectorView was used in a fragment, things become more complex trying to forward the information to the correct view.
Because of this, I instead changed ItemSelectorView to ItemSelectorFragment which can override its own onActivityResult making it, not its owning activity, responsible for updating itself with the selected result. This means it's essentially completely self-contained now.
While this seems to work wonderfully--with this change a user only needs to place the ItemSelectorFragment somewhere in their layout and set the available and selected items--a veteran Android developer here said using a fragment like that was wrong and I should have stayed with a view because of the overhead of fragments.
But going back to a view means I'm back to having to get MainActivity involved again, making this much more complex to actually use.
So what is the technical down-side for using fragments like this? I thought that was the entire point of why they exist. And if I am supposed to use a view, is there an easier way to get a result from ItemSelectorActivity?
If I understand you correctly, your view is starting an activity (ItemSelectorView starts ItemSelectorActivity). But views should be dump in Android. They should display, nothing more.
So a view should never start an activity. A view can contain a list of items maybe, but these items should be views and nothing else. Usually we use an Adapter for that: a middle man between the items to be displayed and the views that are created to represent them on the screen.
You could look into MVP to do this in a proper way. Or maybe MVVM and android architecture, if you like that better.
To answer your question, using a fragment for your use case is a better approach then a view and there is not that much overhead at all.
I have a question about the correct logical use of fragments in Android. I know that it was designed to be used to improve tablet experience, but does this imply that fragments should generally ONLY be used for this purpose? Or would it be poor development practice to use fragments as a replacement for a custom compound View?
For example, I am writing an app to keep tally. When the score sheet is produced, it creates a "ScoreCell," a custom compound control, for each player in a ScrollView. What I want to do(but don't see how as a View) is handle internal OnClickListeners that are activated by the containing activity: each ScoreCell has a TextView for the players' name, which I want to long-press to startActivityForResult() to pop open an input dialog to change the name of the ScoreCell. But seeing as the method for OnActivityResult() is unavailable in a View, would it be correct for me to instead make each ScoreCell a fragment?
Here is a picture of the activity to help understand the logic of what I need/am confused about
There are many questions in here, let me go through them.
No fragments are not meant just for tablet experience, in general they allow you to create more modular and adaptable layouts (think classes). They are extremely helpful in tablet layouts/landscape, but also give you reusable components.
At the same time, a fragment is not the right choice here... It is much easier to use a listview, coupled with a custom cell layout. Instead of using another activity to display a dialog simply call new Dialog() and dialog.show(). An activity should only be used as a dialog if it will be used by the user by a long period of time and provides a new "activity" (action)
Items in a list should not each be their own fragment, no. You can pop up a dialog without creating an entire Activity. Take a look at the documentation on AlertDialogs and DialogFragments for your dialogs and you can get the result from that.
I'm interested in hearing what you guys think is the most efficient/solid object-oriented design for a simple multiple choice quiz.
Basically, the app presents a series of questions with 4 choices each. If the choice you selected is correct, then a new activity will display some congrats and full details behind the correct answer and if you're wrong it'll say you got it wrong, along with the details, etc.
After that, the user goes to the next question. On each new question, you'll see your score so far. So maybe you get 50 points for each correct answer, something like that.
Here's how I thought about implementing this: Create a custom view with some radiobuttons or some other widget that could be used for choosing an answer. The custom view takes a Question object, which is just a regular old java object, with fields for choices 1-4. Then, in the custom view, I can set the text of the radiobuttons to the choices from my Question object.
So in my activity it would look something like Question myQuestion = new Question("string for choice 1", "string for choice 2"...)
And then..
Use the question with my custom view. QuestionView myView = new QuestionView(this, myQuestion);
Ok so that's all great. I'm just wondering if I'm setting myself up for trouble. For one, I've got to keep track of the score across all the question activities. Does it make sense to have all of my questions subclass some, mostly empty, activity that I create which can have a counter in it that gets incremented anytime the user gets an answer right (i.e in my superclass activity int scoreKeeper; and in each activity that subclasses this activity: if(choiceIsCorrect) scoreKeeper++). This will allow the score to persist across the activities. I realize I could hold a score between activities by passing and extra to each new activity and then simply adding to it, but that doesn't really seem to make sense to me.
Sorry for all of the blabbering..but I guess my questions are: what do you think is the simplest design for this? Also, in general, I always assumed that you should always use a new activity whenever the user is doing a "single, focused thing"...as the Android paradigm states. But sometimes it feels weird to create so many activities. I know the fact that "it feels weird" is no reason not to do it, but when does it make sense to simply reuse on activity (e.g. in this case, just swapping in a new question in my activity and updating the UI accordingly) as opposed to starting a new activity?
Also, a more detailed question - what would be a smooth way to set which choice (e.g. which radiobutton) contains the right answer, so that when the user presses submit, I can check if they have the right answer and yes/no then react accordingly?
To summarize:
What is a straightforward, object-oriented way to create a succession of multiple choice question activities?
What's the most sensible way to keep track of the score?
Does each question necessarily need to be a separate activity? (And, in general, how do you guys approach the question of whether something ought to be a separate activity?)
Also, kind of a particular: what's the easiest way for me to flag which choice is the correct one so I can check to see if the user got right? I know that with a radiobutton, for example, you can use onCheckedChangeListener and retrieve which radiobutton is currently checked, but I'm not sure how to use that in my design to check if the user got it right...
Thanks!
I would not make the "correct/incorrect information activity" its own activity. Instead, when the user selects a radio button choice, and then clicks an "OK" button, a Dialog should pop up. When they close the dialog, there is a button there to advance to the next question.
I would say you should do this all in one activity.
I'm going to use one activity with a ViewFlipper for cycling through questions.
Sorry, I know that this topic has been covered a bit. I've read the related posts and am still a bit confused. I am working on an app that while the prototype will have 3 main screens, it will eventually have dozens. Each screen will present either dynmically changing status or take user input. To visualize, it is required to be laid out similar to how MS Word or a typical PC is. It has a status bar at the top and a navigation bar at the bottom that is common to all screens (slight tweaks for some screens, like different icons) in the middle is what I would call a view pane that needs to be updated with a applicable layout.
The status, nav bar, and each screen are defined in their own layout xml file. For my first swag at it I just used a ViewFlipper and loaded the 3 screen layouts into it. However that means that currently I have one main Activity which will not be maintainable as I continue to add screens.
It feels right to me that each screen layout should have an associated Activity class that understands how to control that screen. I need to figure out how to load that into the center pane dynamically. However I thought I read in another post that using multiple Activities can be a CPU and RAM drain.
Currently I tried making one of the screens it's own Activity and kick that off from the main Activity by creating an Intent and than calling startActivity. However that causes the new screen Activity to reside on top of the main Activity. The interesting thing is that then pressing the back button dismissed that activity and returns me to the main.
So far I haven't figured out how to setup having a different Activity control what happens in the center pane.
If I continue down the multiple Activity path, should my main Activity be inheriting from ActivityGroup?
Are using View classes more applicable in this case?
I know this has been a long post. I'd appreciate any advice.
Thanks!
CB
As you noticed, Android will implicitly track a stack of started activities in a task, and the 'back' button ends the top one, reactivating the next one down. I would advise you to think about which kinds of things the user might expect the back button to do, and make it so that activities are separated along those lines.
I haven't played with ActivityGroup so I can't advise you there. If you go with completely separate activities, you can have them all use the same "shell" content view with the common nav/status bar. Have a superclass or utility class handle populating and managing that from there. Then use a a LayoutInflater (you can call getLayoutInflater()) to fill in the middle with your Activity-specific view.
If you want one of the activities to have multiple screens, you might still end up with a ViewFlipper in the center slot. Again, you want to have an Activity transition wherever you want the user to be able to go "back"; that also means you may NOT want to have a change of activities in cases where screens are closely related or part of the same logical thing-being-done. (You can override the back button's behavior, but unless you have a good reason to, it's best to just arrange the app so that Android's basic setup helps your app's UI rather than working at cross purposes.)
If you want to use activities in the fashion you talked about, you might look into using a tab activity. It actually works in the way you want, you just need to hide the tab widget and put your navigation bar there instead. Or, you could go a little deeper and make you own similar tab-like ActivityGroup like Walter mentioned if you have more time.
You could use a view pager with fragments to accomplish the flip between the different views but still allow your activity to have full control over it. The activity can control the menus while the fragment controls your viewing area. This way your back button will properly dismiss the activity containing all pages related to the activity instead of walking down the stack.