I've recently started developing Android Apps, and whilst the model is making more sense the more I look at it, I cannot do something (nor find any reference material on it) which to me seems quite simple.
I have an activity which has five buttons along the bottom, and a blank View taking up the rest of the screen. I want, upon clicking these buttons, for an activity to be opened in (and confined to) this view. I can get a new activity running without incident, but this opens in a new screen.
If anyone can show me an easy way to launch a (sub/child?) activity within a view which is defined in the parent activity's layout xml file - equally, it could be created in the parent activity - you'd really be doing me a favor!
I'd recommend taking a look at TabHost. The tabhost is an Activity itself, and the sub-views are all Actvities as well.
Here is a good tutorial that'll get you going very quickly. There is a more work to create (optional) icons for the tabs (also describe in the tutorial).
Hope this helps.
Edit* You mentioned buttons being at the bottom of the screen. Take a look at this SO Question
You can achieve that by using an ActivityGroup... here is a simple example which shows how to do it using a TabActivity:
http://web.archive.org/web/20100816175634/http://blog.henriklarsentoft.com/2010/07/android-tabactivity-nested-activities/
Of course, you will have to change the code since you are not using TabActivities. Just take a look at the getLocalActivityManager and getDecorView methods that is what you will be using.
Related
In an app I am working on, I'd like to have a bar with some controls always present at the bottom of the screen. It should overlay every activity in the app but also be able to disappear and reappear. To do this I've considered some options, such as simply using a linear layout and setting the visibility in every activity or using a fragment somehow. Probably those would work but I feel there must be a better solution. So my question is: what is the best way of doing this?
There are two ways you could do this. You could just use Fragments, and make your overlay be a fragment.
The other way would be to sublcass Activity with an AcitivityWithOverlay, which handles the overlay appearing and disappearing then have all of your activities inherit that. If I did it this way, I'd make my overlay a singleton so I wasn't creating extra versions all over the place that did the same thing.
I'm new to android programming and I'm having a little trouble with the following.
I'm trying to make a menu for a game, and I'd like to have an OpenGL view running in the background (with a running demo of the game) and then have the various menu screens change over the top of this; without reloading or affecting the OpenGL view.
At first glance it appears I have a choice of two methods: the first to use separate activities for each screen and then load each individual menu from xml layouts. This obviously reloads a new instance of the OpenGL view per activity. The second option would be to use a single activity and inflate each XML layout on request, leaving the OpenGL view running untouched.
If possible I'd like to use the first method, but as stated all the views end when a new activity is loaded. The second method I think should work - but then I have all the code for the entire menu in a single file. I'm pretty sure I'm missing something.
If anyone can recommend the best approach for this it would be appreciated.
Thanks.
P.S - I guess the desired result is that similar to the Angry Birds menu which has the continually scrolling landscape in the background.
Use Fragments. You can keep one Activity (you'd have to re-initialise openGL for each activity otherwise), and then have different fragments pop up over your openGL stuff.
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.
On my application I'm developing, the main.xml layout (the default layout of my app) has a few buttons that have been assigned onClickListeners (not the implementation way).
One of those buttons I want to have the ability to take you to another view. On the other view (preview.xml), there's another button that takes you back to the main.xml view.
I've used setContentView in the onClickListeners of those buttons and this works fine so far, but after you click the button that takes you back to main.xml, the buttons on main.xml have lost their onClick functionalities.
How can I get this to work right? I presume using setContentView isn't the right way to do this.
Your best bet, at Konstantin says above is to use Activities, as you will come across these a lot whilst developing for android. you can read about them here Activities. I assume you want to pass something onto the preview.xml page? If so, I'd recommend either putting it as an extra in the Intent used to start the activity (see the link) or creating a static reference in the activity (which you set before you launch it).
I'd say use two different activities and switch between them. Another option can be ViewSwitcher.
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.