Android :: Design Pattern For Extending Droid's Activities?
Apr 28, 2010
While programming on Android, I end up writing a parent activity which is extended by several others. A bit like ListActivity. My parent activity extends Activity. if I intend to use a Map or a List, I can't use my parent activity as superclass - the child activity can only extend one activity obviously. As such I end up writing my parent activities with the same logic for Activity, ListActivity, MapActivity and so forth.
What am I looking for is some sort of trait functionality/design pattern which would help in this case. Any suggestions?
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Apr 6, 2010
I've got a common task that I do with some Activities - downloading data then displaying it. I've got the downloading part down pat; it is, of course, a little tricky due to the possibility of the user changing the orientation or cancelling the Activity before the download is complete, but the code is there. There is enough code handling these cases such that I don't want to have to copy/paste it to each Activity I have, so I thought to create an abstract subclass Activity itself such that it handles a single background download which then launches a method which fills the page with data.
This all works. The issue is that, due to single inheritance, I am forced to recreate the exact same class for any other type of Activity - for example, I use Activity, ListActivity and MapActivity. To use the same technique for all three requires three duplicate classes, except each extends a different Activity.
Is there a design pattern that can cut down on the code duplication? As it stands, I have saved much duplication already, but it pains me to see the exact same code in three classes just so that they each subclass a different type of Activity.
Edit: Since it seems I need to be a bit more specific...
Suppose I'm trying to solve the problem of an AsyncTask background download during orientation changes. The solution I have right now is to use callbacks; there's download manager that I have which starts these downloads, and then I have the Activity attach a callback to it. When the orientation changes the Activity is destroyed and then recreated; during this process I detach the old Activity's callback, then attach a new callback from the new Activity afterwards.
Orientation changes are a common problem, and in multiple Activities I start the Activity with a progress view while the data loads. What I am trying to solve is not having to re-implement this orientation-handling logic ten times over; my initial solution was to subclass Activity, but then I got the problem above.
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Feb 23, 2010
Does the Android platform lend itself well to a particular style of UI programming like MVC or MVP? Most of my UI experience is with spaghetti code on a very old embedded device or in GWT with MVP so I do not know where to start.
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Aug 23, 2010
I fight with me for some days about asking this question.
Its pretty plain and simple:
If you have an application with a GUI totally working on 2D drawing, what should be the best practice to handle what to draw and where to touch?!
Some example for better understanding:
I have a game with a map. On this map I can build houses and stuff.
I also have a information bar which can be extended. On the extended bar I draw some information about the game and also enables to change different values. If a touch occurs, I have to check, if the information bar is extended or not to determine if I want to change something on the map or something on the bar.
Thats done by the State Pattern, but I have some doubt if thats the right one because I think it can be a bit complex because of possible "sub-states".
So basically the question: Is the State Pattern (from GoF) the best practice to handle a pure graphical GUI?
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Oct 29, 2010
I have several related database tables and I would like to treat their rows as objects and their tables as something like lists. What are the considerations that I have to keep in mind (for instance, ensuring that the objects stay consistent with one another and with the database, lazy loading)? And what is a good design pattern for implementing this? As I imaging the answer is pretty involved, a link to a good website would suffice.
On the other hand, if someone knows of Hibernate-like thing that really works on Android, I might give that a whirl (although it's a little heavy weight for me right now).
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Nov 22, 2010
I am designing an app that will have some activities separated in tabs. Some of them will have to perform tasks in the background will the user is in another tab. What is the best strategy for designing an app like this? I was thinking about using a service but it can be killed by android dalvik, isnt it?
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Sep 6, 2010
As i am building multiple activities, i realise that i have to code out repetitively this segment.
CODE:.......
So that i can return to the home page.
Is there some structural pattern or design pattern that i am missing out? Like a Activities Manager that manage all the activities?
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Sep 18, 2010
Basically, we are maintaining the sessions for the specific user's environment. For that, Three basic stuff we have to maintain. That are Login, Session check and Logout.
In Android, Each screen designed by Activity. we can startActivity() and finish() a current Activity. But you can not do that Previous Activity.
UI Design of APP:
Login(Main Activity)-->Home(Child Activity)-->It contains Profile, add data, settings,etc.(Sub Child Activity). All Screen has a Logout option in Menu.
The Problem is:
When i select a Logout. The App gets Logout. But I can not navigate the App to the Login Screen. The Previous child Activity did not finished from the Activity Stack.
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Nov 23, 2010
I am going to develop an Android Application but before developing it i needs to have MockUp for the Android Application,so is there any way to design MockUp/GUI Design tool for the Android Application?
I know about DroidDraw tool , but i think it is not the exact way to prepare Mockup for the android application.
I have already referred this SO Question , but overthere i just found all the tools for the I-Phone only. So please feel free to share with me if you have/found any !
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May 1, 2010
What happens if I enabled the pattern lock by updating the setting LOCK_PATTERN_ENABLED, but have never set a pattern? I would check, but I don't want to reset my phone (I don't see a way to clear the lock pattern). Does anyone know?
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Dec 11, 2009
The subject is pretty much it. With pattern lock security enabled, what happens during an incoming call? Must you enter the pattern to pick up the call, or can you simply press "Send"?
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Jun 30, 2010
how to call BarCodeScanner, and return the value to a field.so now, i have a toast that says "successful scan" and then i want to pass the result to a new activity. when i comment out my intent, everything works (minus the passing of data/switching of screen, obviously) but when i run my project as is, it FC's no errors reported by eclipse in code or xml. any insights?
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Nov 29, 2010
Is there a lock pattern on the DHD, the one where you swipe it in a certain pattern like I saw on the original desire?
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Sep 3, 2009
I have done a small app for the ADC2 and now i want to make a free light version for the Android market and one full version that will cost some cents.
My question now to all who have done something similar: How have you designed your application(s)? I have thought about a few solutions to this problem:
1.) Duplicate the code in two different android projects Not a very good idea, duplicate code is always bad.
2.) Create some sort of library to use in two different projects. With this i could share the business logic of my app, but not the activities (at least this is what i think) And using the activities from one project in another project would be great.
3.) Include all needed code (business logic, activities, ...) from one project (the full version) in my light version. This way i would achieve some sort of new "view" to the code basis. This would be the best solution i think, but i do not know how to achieve this.
So to everybody who has done a full and light version of one and the same app: How have you done this?
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May 6, 2010
I have tried DroidDraw and the Eclipse layout editor and both seem very difficult to create anything other than very simple layouts. I find myself dropping back to the XML file to be able to manipulate it.
Has anyone found any good tools to design the actual screens? I am not looking for a mock-up tool... but an actual tool to create the XML layouts.
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Jun 30, 2010
I'm using Relative layout for designing UI. Please give me guidelines to follow.
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Oct 13, 2010
What are the best practices to design webservices for mobile (particularly Android) apps?
Personally I'm focused on using JSON (and not XML) and I try to make it the less verbose I can. But I'm probably missing a lot of things.
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Aug 2, 2010
I'm a web designer by nature, accustomed to changing resolutions and font sizes, but I'm unsure how to design for the Android platform without knowledge of screen sizes, especially when the screen rotates from portrait mode to landscape.
Should I just do generic things that tile, or is there a way to design things of static size?
By this, I mean for the GUI and graphics, not element nodes of the XML.
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Sep 8, 2010
This was working fine when I first started the project. I am referring to editing/adding to the strings.xml file. It used to display a design and XML tab that allowed me to update it. now its just showing up as a table. Any ideas? I don't understand how I could have messed this up. I did check in another project of mine and I am getting the same results so I don't think it has anything to do with the XML.
Any ideas? Thanks!
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Nov 3, 2009
I'm just getting into Android development, coming from a mostly ruby and scheme with some Java background. For a first project, I decided to try and build a stopwatch.
The included Chronometer widget doesn't quite have the functionality I wanted, so I copied its code into my own package. However, when I try to build it, I get the following error:
CODE:...............
If I remove the RemotableViewMethod annotation, the code compiles, but crashes with an IllegalStateException as soon as I call a method on the widget, as seen in this stacktrace: http://www.pastebin.org/50243 .
Looking through the android source, you can see stock widgets using the RemotableViewMethod all over the place, but for some reason, my code can't.
So, my question is this: What can I do to enable the RemotableViewMethod annotation in my custom widgets? Is there something I should be doing differently in order to code custom widgets?
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May 8, 2010
I have trouble (example<http://groups.google.com/group/android-developers/browse_thread/threa...>) wrapping my head around styles/themes. Can somebody help me or point me to actual documentation?
Let's say I have a drawable that I want to use as the background of a layout:
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle>
<gradient android:startColor="#9F9FA4" android:endColor="#66FFFFFF" android:angle="270" /> </shape>
Now I want to have a dark and a light theme. Depending on the chosen theme I want to have a different value for startColor and endColor. How do I do that? I am aware of extending themes, but what do I put into the items? How do I reference those new values then?
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Jul 8, 2009
I want to extend the built in media player, however when i grab the sources, there are a lot of external dependencies that are hard to track down. Is there any way to get the source and the dependencies so that i can have it as a standalone and then extend it, is this even possible?
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Oct 14, 2009
I know this question was asked couple of times in this list, but I haven't found any answer in archives, and last time this subject was debated almost a year ago. Does anyone knows is it now possible to somehow extend contacts functionality (for example: add custom field for VoIP phone number in which case user can use it to start custom activity for voip)? What are Contacts.ExtensionsColumns for?
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Sep 19, 2010
I get a result as http://i3.6.cn/cvbnm/e1/71/e9/19008bd7258eaf858be73dc6431b1f8b.jpg,
i want to get two tab,could you help me? Code...
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Nov 24, 2010
Ultimately I wish to produce a compressive Contact Manager with some specific features. I thought it would be good to experiment by extending Contact. So using git I checked out froyo-release and tried to build it. That didn't work so well as it contains things like
Suppress the internal stuff under the assumption that I really don't need it. Start with a toy Contact Manager and implement (reinvent) everything.
My guess is that I am going about this incorrectly. "I want that third alternative" --kirk.
Just for completeness, the new special behavior is to provide an action list for a contact based on the types of that entities data.
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Dec 18, 2009
I built my own car mount and want to get your opinions on it. I wanted to design myself because I REALLY didn't want another thing sticking off my windshield or out of a cup holder. This a the 2nd version of it and I am already planing the next version to be a solid black Plexiglas instead of the clear. I didn't count on the tape I used to be gray. Take a look and let me know what you guys think.
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Jul 18, 2010
Lot's of talk about the speaker volume/tone on the Droid X.
I too am a bit concerned with the speaker volume and tone on my Droid X.
I did a test. Droid X vs. Garmin Nuvi GPS - Google Nav vs. Garmin built in maps.
I plotted a route across town and fired up both units in my car. I turned on my car radio. I started to drive.
Results:
1. The Garmin was louder and clearer than the Droid X when speaking turn by turn instructions.
2. The Garmin was loud enough while listening to the radio.
3. The Droid X was not loud enough to be heard over the radio(volume set to max).
I don't want to plug my Droid X into the AUX on the radio because I then lose use of the radio.
Is this a hardware issue in the Droid X or something that can be fixed by a software update?
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Oct 31, 2010
Im using the NotePad example as a base for an application. This binds a ListActivity to a Provider.
Its perfect, except it uses SimpleCursorAdaptor, which means the list only binds to and displays one item per row. I want it to display two items, both bound the Provider. Or more accurately display the text from one Content Provider field and an icon which depends on the value of a different field.
This sounds like a pretty simple thing to do, a very slight modification to the NotePad application. Trouble is, I have no idea on *how* to do it. I really need a starting point, and "approach" to use.
So far I have tried (unsuccessfully):
* Hand populating the ListView by reading in the Provider data and populating an array in OnCreate. This works, except as the data is not bound the List does not update when I add an item.
* Extending SimpleCursorAdapter with a custom getViewBinder. Could still only bind to a single column.
* Building my own ListAdaptor. Couldn't get this to work.
* Concatenating both fileds together and "parsing" 2 fields into 1 field read/write.
The next thing I will try is extremely tacky running two separate simpleCursorAdaptors in two views in a Linear Layout, fudged so the row height is identical, and duplicate the logic.
I say this only to show that I really, really have tried.
How I can create a custom CursorAdaptor which binds to two fields instead of just one like SimpleCursorAdapter?
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Dec 14, 2009
Is there a way to extend Webkit on Android? Can we write plug in for webkit in android? Can we do things like creating our own renderer for a particular type of data embaded in the webpage? Can we track user session or modify data stored in the browser cache/memory?
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Nov 9, 2010
I have an application with various tabs (on a tabhost), each tab is an activity that extends activity, and haves some textfields and things on it
now i need that my tabs have inside a listview, but in the example from android developer guide says that you have to extend ListActivity and not Activity
basically i need to merge these two tutorials:
http://developer.android.com/resources/tutorials/views/hello-listview.html
http://developer.android.com/resources/tutorials/views/hello-tabwidget.html
i want to know how can i use a listview without extending listactivity on my class
someone knows? code...
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