Android :: Design Approach - Web Service And Broadcast Receivers
Sep 23, 2010
I am developing an app for android mobiles that communicates with a json/rest web service. I need to make certain kinds of calls periodically to the server to check for some information. Within that context I might need also to query the GPS for the current position. I'm quite undecided to use a Local Service, since I don't know very well how to deal with them, in fact I need to retrieve those data periodically and refresh a MapView accordingly. I heard that I can use PendingIntents,in the service, associate this data as a payload and send them to a broadcast receiver which unpack the data and refresh the UI, I heard also that this is a bad design approach because of what broadcast receiver are intended to be used for.
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Sep 9, 2009
I had one question: Is it feasible to use a BroadcastReceiver as a glue layer between the user interface and the underlying business logic ? Example use case: Suppose i am maintaining the state of a call, and providing callbacks to the UI by invoking sendBroadcast with the relevant intent. Similarly, my underlying business logic can send broadcasts to the activity that has registered for receiving it on certain events ( like call connected, connecting, timed out etc).
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Dec 30, 2009
Is it possible to use just a broadcast receiver without any activities? I just want to run some sample code only when the phone receives a call and nothing more. I use Log.d to write out but I don't see anything in the log. Am I missing something here? I also have permissions set in the androidmanifest.xml to allow for these type of intents.
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Mar 16, 2010
something weird just started happening. my app has a broadcast receiver which may access the network when invoked. the code has been solid for ages, but in the last few days it has started getting DNS errors on perfectly fine hosts. these are hosts which can be reached without problems in the main app or from other apps.interestingly i've seen another app get DNS errors too another app with a broadcast receiver.seems to affect all OS versions -- we have 1.5, 1.6, and 2.01 here. i don't have a Nexus to test 2.1, though. are there caveats to doing network inside broadcast receivers? i didn't think so, as ours worked fine until the time change [fx: twilight zone theme]
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Apr 21, 2010
Can anyone give a hint if you know why there are some ACTIONS that do not trigger their associated receivers when they are registered in the manifest while they are received when they are register through registerReceiver() ? For instance, when I declare: <receiver android:name=".MyReceiver"> <intent-filter> <action android:name= "android.intent .action .NEW_ OUTGOING_CALL" /></intent-filter> </receiver> if the application is NOT running My Receiver is never invoked. But now, if I register the intent from inside a service, MyReceiver is invoked properly
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Jul 17, 2010
im trying to understand what the difference between a service and a broadcast receiver is,as i see it they can do the same thing.For example i have an application : App1 That provide a service called ToastHelloWorld which just creates a Toast and stopSelf(). expose it to other applications using an intent filter with the action name: "com.test.HelloToast"Now i have another application : App2 i want to implicit use a service with the action "com. test. Hello Toast" so i call startService( new Intent ("com. test.HelloToast"));and it works.Why would i use broadcast receivers when i can do everything with services and dont have the restriction of a 5sec execution limit?.I know most "system events" is exposed via broadcasts' but couldnt they just aswell be published as Service Intents?
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May 4, 2009
I started to implement my own App Widget using the example provided in the ApiDemos. In order to update the Widget efficiently I chose the Broadcast Receiver mechanism. In the ApiDemos there is this ExampleBroadcastReceiver which would (or should) react to changes related to TimeZone and Time as specified in the Android Manifest of the ApiDemos. I have debugged this Example using Eclipse and the Logcat output (provoking changes in TimeZone through the settings) and come to the conclusion that there must be some bug in the app widget framework. The only Broadcast Receiver that seems to work is the AppWidgetProvider itself. For instance I would expect something like: D/ExampleBroadcastReceiver intent=XY in the logcat's output after I have provoked the event XY. I have even tried without the 'enabled' option in the receiver's specification in the Android Manifest.
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Jun 28, 2010
The online android documentation says: Everything you can do with AppWidgetProvider, you can do with a regular Broadcast Receiver.So, what i want to do is to register via registerReceiver() another event other than ACTION_APPWIDGET_* on my Widget. For example ACTION_BATTERY_OKAY, is there any way to do this? Obviously i cant register the event from the onUpdate() code but i should do it using a service or something else. The problem is that im not able to find any reference to the Provider (AppWidgetManager only returns AppWidgetProviderInfo objects).
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Jul 2, 2010
I have a program that monitors incoming SMS's, and I want it to monitor them full-time, so I registerReceiver with a Broadcast receiver that I've created. The problem is, if I want to unregister that receiver, I can't unless I know the original Broadcast Receiver class I registered. This is not a problem if I set it to stop when the program stops, but I want the receiver to keep running, only stopping when the user specifies. EDIT: Or is there a way of "Storing" the Broadcast Receiver class that I've created, such that when onDestroy is called it can be saved and when create is called again it can be pulled out.Is there any way of doing this?
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Jul 22, 2010
How to set a priority for multiple Broadcast Receivers when dealing with ordered intent broadcast?
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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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Nov 1, 2010
In a book I read, the author suggests to extend the application class in order to have a place to be used as a singleton. In this way, it is easy to make some initialization stuff in it onCreate().Now my question: if my application has also some broadcast receivers declared in the manifest, and the application was not started explicitly, or it was but then the os reclaimed it resources back, what will be happening if the broadcast receiver is triggered? Will the onCreate of the application class be called first?
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Mar 25, 2010
Currently my application is configured to always receive the CONNECTIVITY_CHANGED action to force an update if the previous update failed because there was no connectivity. What I don't like about this is that the broadcast receiver gets to be called too many times although it is not needed. I was thinking to register my broadcast receiver only if an update failed using the Context.registerReceiver(BroadcastReceiver receiver, IntentFilter filter) method. But I'm not so sure if this is a good idea. I'm concerned that if my application is evicted from memory the broadcast receiver will be unregistered or lost and my application will not be notified about the future CONNECTIVITY_CHANGED actions. The update is done in a short lived service. So if the update fails, the service will register the broadcast receiver just before it ends its execution time. Can somebody explain what happens to my broadcast receiver after the application is evicted from memory?
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Oct 25, 2010
I'm working on a project where I need to run the BroadcastReceiver for a third party library for a specific Intent. I also want to run some of my own code when the Intent is broadcast. If I supply my own BroadcastReceiver for the same Intent, it seems that only, one or the other runs, but not both, depending on which appears first in the AndroidManifest.xml file. Is it possible to register multiple BroadcastReceivers for the same Intent in the same application and have them all run? AndroidManifest.xml snippet
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May 20, 2009
I've had an issue where no matter how I've tried to set it up I'm finding the Broadcast Receivers aren't receiving any Pending Intents. A look through LogCat confirms that the intents are launched, but they're not being executed. I managed to make a simple(ish) repro case. If you take the SimpleWiktionary widget by Jeff Sharkey http://code.google.com/p/wiktionary-android/ and make the following changes plus any required imports. Code...
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Oct 29, 2010
Is there a way to capture a key event from the Menu button using an Intent or Broadcast Receiver? Basically I want my app's Service to be activated when the Menu key is pressed.
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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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Sep 29, 2010
I'm designing an android app which will need to do the following steps:
1. User pushes a button or otherwise indicates to "sync data".
2. Sync process will use rest web services to move data to and from the server.
3. The data will be stored locally in a sqlite database.
4. The sync process should provide status updates/messages to the UI
5. The user should not be allowed to wander off to other parts of the application and do more work during the sync process.
The first time the sync process runs, it may take 10-20 minutes. After the initial sync, less data will be transferred and stored and I expect the process to take 1-2 minutes or less. I've been doing a lot of reading about android's AsychTask and various examples of using a Service. But I don't fully understand the design considerations and trade-offs of choosing one design over the other. I currently have my demo project stubbed out using an AsychTask. After watching (most of) Developing Android REST client applications:
http://code.google.com/events/io/2010/sessions/developing-RESTful-and...
I'm left confused the design patterns described here feel overly complex, perhaps because I just "don't get it" yet.
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May 28, 2010
A new question about android and services. Currently I'm developing a App that should send images to a server. It should also be possible to send more images parallel. I made a service that creates for every image a new image. The activity can bind to that service and gather information about the progress. I want to show the current status for every image in a notification (and when the user clicks a notification, an activity with the progress for that image should be shown). But I get several problems with that approach. There are errors with binding, the notification pending event starts the activity completely new, so I lose information about currently sending images and so on. How I could design in a appropriate way.
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Dec 15, 2009
I need to be able to handle/catch Intents while my Activity is closed. So I am looking at either a Service or a BroadcastReceiver. Is it possible to "receive" intents to a service itself? I tried to search, but could not find anything helpful. With a BroadcastReceiver, I am not exactly sure how that works outside of an Activity. Does it depend on the Activity being open/running? Can it run by itself?
Let's say that my Activity is killed by Android(or a task killer app), does the BroadcastReceiver still receive intents and process them? I have used a BroadcastReceiver as a widget, but I do not want to use a widget this time. My goal is to have the user open the Activity to set some options. From there, they would be able to close the Activity, but I would still be able to process Intents that were sent out by the system. I am still fairly new to Android development, so I could be so far away from where I need to be.
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Jun 23, 2010
I am starting to develop a new app and I am a bit confused about the structure I need to give it.I need to react to broadcast intents, so I placed a broadcast received in the manifest. Every single intent produces an action to be performed. Now the first question: should I start a service (maybe with non_sticky option?) or should I start a thread (or an async task) directly from the broadcast receiver? If I start a service, should I do all the stuff in its body, or should it start a thread. I should do the heavy job in a thread if there are time consuming operations, but what if the gui of my application is just an activity with the options and a button to start the service. What is the point in keeping the main thread busy? Do I risk to be killed for not being responsive? I read here and there that I can update the gui from a background thread. Can I do that even if it is started from a service? The AsyncTask's onProgressUpdate is said to run in the application main thread, but if the application is made of different activities, who tells me which activity is the user looking at while the thread is doing all its long work? The user could change activity in the meanwhile and then the update would be unuseful.I know it's (quite) a lot of questions, but I need to get some clarifications before taking the wrong path.
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Jan 20, 2010
I'm hoping to do some audio processing in a remote service (service I've spawned onto its own thread); this will basically occur in a while (1) loop so constant processing. Occasionally I want to provide some information back to the activity that is bound to the service; I'm doing this by sending a broadcast from the service, that is received by a broadcast receiver on the activity, which then uses the activity's service connection to call into the service and get the information needed; at this point the broadcast receiver makes an alert dialog presenting the information to the user.If I stay in my while(1) loop after raising the broadcast, the action in the broadcast receiver never seems to occur.This is confusing to me since the activity and service are in separate threads.If I end the loop after raising the broadcast, the desired behavior on the activity side occurs, but of course this isn't acceptable since I need to be doing constant processing.
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Mar 17, 2010
I have a single Activity application, within it I have a service which creates an AlarmManager and sends a broadcast to a broadcast Receiver.If the activity which starts the services dies, (ie. divide by zero), the broadcast receiver stops the old service which created the AlarmManager.It works the first time. The second time, it does not.It seems like the AlarmManager is still active but the broadcast receiver is no longer receiving. It works great once!
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Aug 17, 2010
I have a widget which starts a service. The service registers two broadcast receivers. I would like to send back intents from the receivers to the service, so that the service can react.I remember reading (on some blog) that this won't start a new service, but will simply pass the intent to the already running service. Is this correct? Is it a bad way of doing it? Is there a better way?
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Sep 16, 2009
The app widget documentation indicates that the "widget provider"being a receiver of a broadcast service may not exist (the process) beyond the completion of the call.If I want to maintain state between two broadcast events, such as say widgetProvider.onUpdate(), can I start a local service and leave it hanging there until my widgets are disabled? If I didn't explicitly stop that service will it be loaded again and resumed when the device wakes up.
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Nov 24, 2010
I'm an android noob that is looking for some advice on how to properly use a service in Android. I am building an app that will connect to a server on the Internet to get a data stream via TCP. That data then needs to get send out to another device that is connected via a bluetooth serial port. I want this to continue to function in the background while the user looks at a different activity. The app will be a NTRIP client, which pulls real time RTK correction data from the Internet and sends it to a RTK GPS receiver that I connect to via bluetooth. The data rate will be about 500 bytes/second. The user interface is a single button to connect or disconnect the data stream and some text to show status of the GPS receiver. There are also a few settings that will need to be configured by the user such as the IP/port of the server to connect to and the bluetooth device to communicate with.I think I need to have the main activity spawn a local service, and then have the service spawn a thread for the TCP stream and another thread for the bluetooth connection. Does this sound right? What is the best model for the service in this scenario?-Start(bind) the service every time the activity starts, and have the connect/disconnect button send commands to the service to start/stop the threads. If I go this route, the service will continue to run after the user disconnects and goes to another app. The service would need an inactivity timer to terminate itself.-Start and stop the service when the user presses the connect/disconnect button. The service only runs when data is moving. If I do this, the activity will need to see if the service is running when the activity starts, in order to know if it should bind to the service or tell the user that the link is disconnected.
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Nov 18, 2010
I have to handle "power down" event in my service, but so far I couldn't find how to receive "power down" event...Do I need to implement "broadcast receiver" functionality in my service? I would appreciate some pointers.
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Aug 13, 2010
I'm trying to figure out if a system event broadcast is broadcasted using ordered broadcast or normal.The event is EVENT_REMINDER and in the source for the calendarprovider i noticed it sets up a alarmmanager to sent the broadcast. I can't find how the alarmmanager sends it. My guess would be as a normal broadcast , But while i was trying some things i noticed i could delay the system's notification (tried up to 10 sec) by building a sleep in my broadcastreceiver. This would indicate that they are handled ordered , and the systems receiver is only called when mine has finished. But can i be sure of this behavour?? (in all 1.5> sdk versions) the docs state that in some cases normal broadcasts are also handled ordered..due to spare of resources.
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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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Sep 28, 2009
trying to create a broadcast receiver which responds to system events and change system settings. I don't need any interaction from the user so I don't need an activity and have been trying to do everything through the manifest file. I've put a log event into my onReceive method but it never logs anything so I'm presuming my method is never called. I've tried this with both the 1.5 and 1.6 SDKs. I was hoping somebody could have a look at my code please and let me know if there are any problems.
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