Android :: Activities Design In Android
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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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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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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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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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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Aug 2, 2010
I'm kind of new to android development.I have read from many sources that findViewById() is a "costly" operation. I'm making an application that deals with 5 TextViews to provide different kinds of information (distance, duration, title, description, etc) from a database. I'm using listeners to catch touch/click events and feedbacks a handler. The main function of the handler is to received a "position" in the Cursor where the new information needs to be displayed. I mentioned earlier that findViewById() is a "costly" operation. So, I don't call this method in the handler. Doing so, it will retrieve every time the Views when user touchs/clicks some widget. Is it right to populate the Activity with private members of the Views/Layout it displays? I mean, I don't like it. I don't know why, but seems that I'm populating too much the activity. I'm aware of the android:onClick xml attribute, but in my case I also use long click listeners. So, a piece of onCreate() looks like: And all of those are private members, wihout mention the "cursor.getColumnIndex()" for each. I thought on implementing Handler.Callback and set on the Hanlder.Callback constructor implementer a View array or a View list or something, but I also need this objects later to set other listeners and setups. Is this right? I cannot think another way, as I need the reference to the object, and also the Cursor reference that the handler will move to the "position" provided and update the correspondent View. I will really appreciate either an advice or a useful link/info/doc to read in what concern in this kind of designs. What I do not like is that It looks like imperative programming filling the Activity with "global" variables.
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May 13, 2009
in Android code, It is a very strange concept to define the APN type (APN_TYPE_MMS). The reason are: 1) APN only is an access pointer, it haven't any special attribute for MMS or other things. 2) Only Application care the APN name, since different APN will provide different service from operator. for example, operation may provide Email/MMS/GPS/.... service on different APN. 3) Android only define one type APN_TYPE_MMS, this will limit other top application usage. Any one can answer me why Android design this way? If google have strong reason for such design, I hope add other user defined type like APN_TYPE_USER1 APN_TYPE_USER2 then top application can set his property to use its APN other than APN_TYPE_MMS
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Oct 13, 2010
I am a developer and recently completed the implementation of my keyboard MessagEase. It's available on the Market (with its very- different features, making it quite unlike QWERTY).
This keyboard works fine as a replacement of the standard keyboard on an Android Phone. But for a An Android Tablet, it would work best if it's implemented as a floating, movable keyboard.
(the footprint of this keyboard is mostly dependable on the size of a human's finger; it remains the same even if the tablet's display is much larger than a phone's. Therefore it'll take a relatively smaller area on a tablet.)
If I use the current SDK hooks, it will have to take a significant portion of the screen, defeating the purpose.
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Mar 3, 2010
I have a service running that grabs the users attention with a notification. What i would like to happen when the user clicks on the notification is for it to launch a dialog box. The "proper" thing to do is to launch an activity in this way, so is there a way to get an activity to launch with out filling the screen? So it looks like a dialog box?
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Sep 1, 2010
I'm more than happy coding apps.I am, however, rubbish at icon design.I'm sure I'm not the only one for whom this is a problem and yet all android devs need to create a launcher icon.Does anyone have any good tips on knocking up simple but effective launcher icons?
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Nov 3, 2010
if this is a silly question, am sorry about that. I was wondering if its possible to design android icons using a 3d modelling package like blender? i know i have to stick to the guidelines documented already, but was just wondering if anyone had come across or done something similar? Its that little part of the icons(launchers) being able to have a slight perspective and looking through the requirements to design icons it seems i might be a lot faster using a 3d modelling package and then following part of the icons template guide(based from my requirement though!).
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Aug 29, 2010
how to use the IMF to design a soft keyboard. Please point me to some resources that will help me understand how to do it from the ground up. Something other than the SDK sample
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Sep 18, 2010
I designed an app for htc desire.The background image used for the app looks good in ecipse layout, when installed in phone it is stretched.
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Jan 5, 2010
I need to design a board UI using android platform. I was planning to take one image as board and moving the required images over the board. How do I achieve the same? I need to find the coordinates for image and need to move the required images to specifies coordinates. Is there any andorid API for this?
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Oct 8, 2009
Is anyone aware of an example or sample code that shows how to make a settings page (like what you get from hitting settings)? Many apps seem to have them but I'm not sure what type of list they are using.
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Oct 7, 2010
Taking into account JIT and non-JIT devices, what would be most efficient on Android for returning multiple values from functions: an array like this: Code...
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Jul 21, 2010
Referring http://code.google.com/events/io/2010/sessions/developing-RESTful-android-apps.html. Can any body provide source/links which implements such a design?
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Aug 30, 2010
I have a general Android design question around data access. I have a number of activities in my application that need to access a SQLite database. In order to wrap up all data access logic in one place I have created a DatbaseHandler class that takes care of all data access logic. This class takes care of building up where clauses, calling the database and interrogating the resulting cursor to retrieve the query results and return them to the caller. The purpose of this class is to wrap all data access code in one place so that it can be easily managed and maintained as opposed to having data access logic scattered across all activities. Each activity that needs access to the database creates an instance of this DatabaseHandler class and passes it a reference of android.content.Context. The DatabaseHandler class then uses this Context object to call an underlying content provider as follows context_i.getContentResolver().query(...).
My data access logic (cursor handling logic to be specific) is not in the activity and so I cannot manage the cursors life cycle, therefore there is likely to be memory leaks.
My questions are as follows -
How can I (if its even possible) manage the cursors life cycle from outside an Activity? Should each activity even be creating an instance of this data handler class and passing an instance of Context to it? Perhaps my design approach is wrong and I should expose these data access functions as static methods that take an instance of the calling activity as a parameter. That way I could perform managed queries and let the activity take care of managing the cursors life cycle?
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Oct 18, 2010
I am working on developing an application that requires me to establish multiple client-server based connections. Connection can be of two types where the Android device can be a server or a client. I can have up to 6 - 8 connections. Once the connections are set-up they need to be running in the background and are not typically affected by UI actions.Since each connection can be blocking, I am wondering what is a good away to design this app. Should I have two services for handling the server and client connections? Each service could have a "connection manager" that can spawn new threads when necessary. Or does creating two services even help? I presume spawning new processed would not be good as they will be expensive. Is this correct? I would appreciate any suggestions. Also, if this use case is not typical please let me know if you need more information to make any recommendation.
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Nov 12, 2010
I need to design an android app to communicate with HID Custom USB Device. Are there any standard java library that I can use to implement this?
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May 7, 2010
I wanted to design a customized text selector that changed the text color when user clicks the TextView. But got the following error:
Code...
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Jan 14, 2010
I am trying to modify the design of Spinner widget. I can change the background, but I can't find a way to change the arrow icon on the right side. Is there a way to do it?
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Jun 18, 2010
I am not able to get an idea of how to do the "Design Process for a Mobile Platform". Can anyone give a little description of how to do the same.
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Jun 8, 2009
I have a specific requirement to design a application for picasa or a browser short cut for the same. If any one have any pointers.
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Oct 24, 2010
I was surprised to see a couple major shortcomings in the design of MapView and MapActivity.
First, MapView requires itself to be hosted in a MapActivity. According to the documentation,
A MapView can only be constructed (or inflated) by a MapActivity<http://code.google.com/android/add-ons/google-apis/reference/com/goog...>.
> This is because it depends on threads which access the network and > filesystem in the background; these threads must be shepherded by the > lifecycle management in MapActivity<[url]...>. > Tiles are cached on the filesystem in your application's directory. The > cache is auto-managed so you don't need to do anything with it, and can > delete it at any time.
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Dec 21, 2009
I've been trying to figure out how to get to the current EGLContext from the GLSurfaceView. I looked at the APIs and looked at the code but it doesn't seem like there is any path to it. I could have just missed it - please correct me if I have, but it wasn't obvious. Now, I can totally understand the designer thinking that we should protect people from the context because they can cause bad things to happen but actually it would be nice to have access to swapbuffers so that we can do some effects. Fair enough, though.
The one thing I wanted was to see the current EGLConfig so that I could find out what config attributes I'm getting on weirdly-behaving devices like the Galaxy. It seemed easy enough - it's passed in to Renderer in the onSurfaceCreated method:
public void onSurfaceCreated(GL10 gl, EGLConfig config);
Great! Except wait, you can't query an EGLConfig without an EGLDisplay and that's locked up in the GLSurfaceView. So why is it passed in to the surface created method? Isn't it useless? Accord to GLES spec, an instance of EGLConfig is only good if you have the display/context instances that it was created from.
I didn't try querying it with the default context because it's supposedly invalid but perhaps someone could shed some light on this? I'd love if it were something dumb and obvious that I don't know about.
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Aug 9, 2010
I understand how to create a custom Android control, and I believe I understand how to pull attributes for it from the Xml layout. I don't know, however, how to get any children elements from it. Here's a visual example of what I'm trying to accomplish: public class Menu extends LinearLayout. When my Menu is created, how do I get references to the two MenuItems. Code...
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Jun 14, 2010
I have an activity which starts a (intent)service. Both access the same DB and potentially write to the same table. What design pattern would you recommand to avoid concurrency?
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Feb 10, 2010
Assuming that old Icon design guidelines are not valid anymore, where can we find information about the guidelines to follow to design "new-styled" 2.X launcher icons?Should applications provide icons for both icon styles if they work for both versions?
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