I want to be able to change which Activity is run when the user runs the application.
I know how to do this in the application's manifest file, but I would like to do it programmatically after install. The reason being, I want the user to be able to choose which screen loads when he opens the application.
How can I do this? The only way I know of seems very clunky: have an essentially empty Activity which has the MAIN intent-filter - which then reads the user's settings and transfers the user to the desired Activity. This creates a lot of mess, like the back-stack needs to be considered, and the overheads of loading one activity straight after another seems wasteful of time and resources.
You cannot change launcher activity dynamically.
As you said it is possible by saving user preferences and start desired activity each time. I have tried it and it is fast enough to not show itself. Don't remember to call finish on main activity. it will solve back stack problem.
Also you can use different fragments for different activities and decide which one should be added to main activity. It may be faster. However as I said it is fast enough to start a new activity and hide main activity because it is done in onCreate method. Don't worry about that.
Related
In my app I am creating a custom preference screen. This screen in reached via mainActivity (launcher). The mainActivity also shows the current status of some of these settings by reading them and laying them on views. Now, when the user will reach one of the preference screens and edit them, by design I aim to bring him back to the mainActivity (it would be intuitive to press the back button). This time however I want to show the latest edited settings.
I am used to putting layout operations in onCreate. But, in this case onCreate will only be called once when the activity starts and read the status of preference settings and lay them on screen. However, when he will open a settings activity, edit them and press back button he will not see his latest settings laid on screen as onCreate need not be called.
So, on what activity callback should I place the operations to read preferences and lay them on views.
This is based on my understanding and I may have messed up big time. Guide me, Thanks...
To anyone looking for an answer. Its pretty basic stuff. Create function in your main activity to read preferences and update your views. Now, start your preference activity using startActivityforResult() and when result arrives from that activity, run the same function inside onActivityResult(). Done.
I am working on an application in android. Where I need to use menu through out application. Actually it will be used for navigating within application from one activity to other and so on... I am wondering that it will need to write onOptionMenuCreat and OnOptionMenuSelect methods in each activity. Also if I make one parent activity where these two methods could be written even then on each activity Option Menu will be created again. So handling same menu while it is created again is becoming work of afaik. Any good design suggestions are most welcomed. Another very important thing how to map that user was on witch activity last time while selecting same menu again. My app has total five menu options so that means there are five different ways to move within application simultaneously.
Please Do tell me solution for both issues. Thank You.
You create the Menu in an Activity and inherit all the other Activities from this Activity.
To answer the second part.
create a different method for each menu handling in the parent activity. If you need a different menu/menu_item behaviour for your activity, just override that method.
I am working on an Android app that has multiple screens the user will need to navigate between and I am curious what the best practices are when switching between those screens. I am torn between creating a new Activity for each screen and simply changing the view (setContentView(R.layout.whatever)). The screens all share at least some variable values so I'm leaning toward changing views and using class level variables, but I'm worried a single activity could become very large and confusing with logic for multiple screens in a single file. I'd like to keep the code clean and separated, but I also don't want to be passing several variables around between views if that isn't needed.
Being new to Android development, I'm hoping some more experienced members of the community could share their thoughts and let me know how best to handle it.
Thanks!
Note:
I wasn't planning on using a viewflipper. My thought was to use a button click event and then call setContentView() to a new view for the page I wanted to bring up next.
Example: My application starts up using R.layout.main as it's view. User clicks the Help button and it calls a method that runs setContentView(R.layout.help); to display the help screen as opposed to switching to a help activity.
You should use an activity per screen as this will make the best use of the framework and allow the OS to selectively kill off screens if things get tight.
If you have a single activity and resources get tight the OS has two choices; kill everything or kill nothing, and if the user is not using your app then it's most likely it'll kill everything.
If you use an Activity per screen the OS can kill off some of the screens the user hasn't visited for a while, whilst still allowing others to remain active which allows the user to go back to them quickly.
As for sharing variables and values, you could use the SQLite database or SharedPreferences stores for passing them around if they are widely shared, or use the putExtra methods in Intent if they're only of use from one screen to the next.
If you have variables that you will reuse make a base class for them, that you will extend.
This can be a your custom activity that extends Activity.
As far I can tell you have to create separate activities for each views, only a few situation can be handled by viewflippers.
This question actually has two parts.
The first part:
I've been developing my first app for a couple of weeks now. I have 5 screens and everything seems well. However, I'm considering changing the app's navigation to a TabView.
I haven't delved much into it, but I'm hoping someone can save me a little bit of time. It seems that people don't generally place Activities inside each tab. They simply point the tab content to a View. This is where my major setbacks are. 1) I already have Activity classes full of code and 2) I can't quickly guess how the structure of an app using TabView looks. For example, where do I put the handler code for clicking a button on a View? Does it all just get dumped into the TabView Activity somehow?
What I would like is if you could please give me a quick synopsis of what I'm looking at doing, answers to any questions you think I may have, and point me toward some resources for creating TabView applications. A quick Google search really just shows me how to create a TabView Activity and add a couple tabs to it. The code doesn't go any deeper. For example, say I have a layout xml to show in one of my tab's content pane, where does the code go for clicking a button I have in that layout?
The second part:
I've added a TabActivity to wrap the Activities I currently have in. At the moment I have Activities populating the content of my tabs (though ultimately I'd like to do this in the most efficient fashion, which doesn't seem to be having Activities be tab content). I've noticed something rather annoying. My MAIN Activity is an Activity I wrote for my user to log in to their account. After logging in, they are taken to my Tab Activity. Here is what happens:
When I am on my Tab Activity and I "minimize" the app by clicking the Home button and then launch it again, I don't get taken back to the Tab Activity. I get taken to my log in Activity. Why? I don't have the launchMode of my Tab Activity set to singleInstance... or is it singleInstance by default? How can I make the app re-launch showing the Tab Activity (ideally by setting some parameter, assuming I'm doing something wrong, and not having to save this data off somewhere and reading it and programmatically telling it what to go to)?
Thank you for all your time and help
I don't have a comment on the advisability avoiding the use of sub-activities in TabActivity. As for handlers -- if you aren't going to embed views instead of activities, then all the android:onclick type handler settings in your layout XML will call methods on the TabActivity. This is because they go to methods on the views' Context, which is the generally the nearest containing Activity. If you want to split your code up further without using Activities, I believe you'll have to use findViewById calls on the tab content views after you've set them up, and bind the handlers manually from there in your code.
I have an NoContentViewActivity which has no Content View (i.e. I did not call setContentView() in the onCreate of my Activity).
My question is how can I keep the content view of the launching activity on the screen? Right now, I am getting a blank screen whenever I launch NoContentViewActivity? I want the content view of the launching activity (the activity which start the NoContentViewActivity) to show on the screen.
Thank you for any help.
Excuse me, people, but my guess is that hap497 wants exactly the thing he wants. There is a bunch of situations where invisible activity would fit while Service will not.
Imaging you want to show a set of dialogs, each next of them is shown after the previous one based on the user choices. And imaging you want to have this (exactly the same) functionality to be available when pressing different buttons on different (lots of them) activities.
To write the same dialog processing logic would be an overkill whether the transparent activity will deal nicely...
Anyway, as stated above, all you need to do is to specify:
android:theme="#android:style/Theme.Translucent"
or
android:theme="#android:style/Theme.Translucent.NoTitleBar"
(if you do not want a titlebar either)
It sounds like you'd be better off using a Service than an Activity. Activities are for code that is to be viewed; Services are for code that runs without a UI, which is what it sounds like you want.
An Activity with no Views assigned is an empty black screen, so it will still obscure the calling Activity. You could make your Activity transparent by assigning it a transparent theme:
android:theme="#style/Theme.Translucent"
Keep in mind though, that your invisible Activity will have focus, so the user won't be able to interact with the Activity underneath.
Why do you want to create a fully transparent Activity? As Daniel suggests, a Service might be a better solution to your problem if you genuinely don't want any user interaction.