Android : Is It A Good Practice To Create A Reference To App Context?
Jun 7, 2010
I have to use context in many places of my code such as database operations, preference operations, etc. I don't want to pass in context for every method. Is it a good practice to create a reference to application context at the main Activity and use it anywhere such as database operations? So, I don't need some many context in method parameters, and the code can avoid position memory leak due to use of Activity Context.
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Oct 1, 2010
I have a button that says "Sort" and when a user normal/short presses the button, I want a menu to appear with the various sort options. Looking around online there doesn't seem to be a straight forward answer to which route is considered best practice. I'm looking to have a menu that looks similar to this: For an example, click the Layers button in the Google Maps app. It opens a list of options on a single short click. It has a title at the top and icons for each option. (The icons aren't super crucial) Should I use a Context Menu? If so, how do I do it without a long press. Should it be a Spinner? If so how do I change the appearance to use a button instead of the normal drop down box.
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Oct 19, 2010
In my Android application, I have to call the getSharedPreferences in non-activity classes. In order to avoid passing a Context object to each constructor of these classes (and because many of them are classes with only static methods which don't have a constructor), I have implemented these steps : The main activity of my application (which is launched at startup) is called Dispatcher. In the onCreate method of this class, I keep a reference to the created Dispatcher object in a static public variable of the Dispatcher class which can be accessed from any class in the project.
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May 15, 2009
When you are developing on an application level(Services, Activities) you always get this Context reference automatically. But what if I am on a lower level and developing a program started with app_process, how can I get hold of a Context then? Its a huge part of the API that need this context. What the proper way to create a Context instance?
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Apr 7, 2010
I am using XML file for creating Context Menu for my ListView. (Please see below). I also want to set a header for this Context Menu. I read (at http://www.mail-archive.com/android-developers@googlegroups.com/msg43062.html)that I can use menu.setHeaderTitle(myContextMenuTitle) in onCreateContextMenu Method. But I need to set this in XML file. How can I accomplish this?
Following is code for onCreateContextMenu Method, correct me if I am doing anything wrong. This is my context_menu.xml file:
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item android:id="@+id/open" android:title="Open"/>
</menu> Code...
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Oct 15, 2010
I'm getting all kinds of errors when using res/menu/menu_home.xml, and my project won't build. That's when I remembered that there was a way to create menus from java code instead of declaring it via xml. Does someone remember how to do that?
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Sep 4, 2010
I have 1 activity, but would like to have multiple context menu's for different UI components.
For example, I have a ListView which will react to:
CODE:...................
How can I create another context menu for the onClick event for an ImageView I have?
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Jun 17, 2010
Is it possible to create a dynamic context menu in android? What I mean is, for example, if I have a list of items, that can be in two states: "read" and "unread". I want to be able to bring up a context menu with an option of "Mark as Read" for the unread items, and "Mark as Unread" for the read items.....
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Aug 20, 2009
This maybe against the way the Android team wants this to work, but if not I can't seem to come up with a way to do this. Basically I have a list view that I want to create a ContextMenu when onListItemClick received. So when the user clicks on a list item I want them to choose the action from a ContextMenu. Anyone have an example of how to do this, I can get it to work with no problems with a long press, but my users are missing the menu and just thinking the ListView does nothing.
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Sep 1, 2010
is it possible to start a context menu on the onCreate method? I know its probably bad design ethics but I have my resons! I've tried the: register For Context Menu (this.getCurrentFocus()); But its not working.. So does anyone have any better ideas?
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LinearLayout layout = new LinearLayout(this);
layout.setLayoutParams(new
LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
//Button button = new Button(this);
//button.setLayoutParams(new
//LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
//button.setText("my button");
TextView text = new TextView(this);
text.setLayoutParams(new
LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
layout.addView(text);
setContentView(layout);
registerForContextMenu(text);
openContextMenu(layout);
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Sep 13, 2010
I'm trying to find a good To-Do list/hierarchy list/Outlined List which would allow me to create track projects in outline fashion. Anyone using anything like that?
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Jan 21, 2010
How can I launch a contextmenu from a contextmenu? I'm trying to replicate the MediaPlayer action that happens when you long click a song, then click "Add to playlist" in the resulting contextmenu. When you click that menu item, another contextmenu pops up with "Add to playlist" as the title, and "Current playlist", "New", and however-many-playlists-you-have defined after that.
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Aug 2, 2010
I have a sizable install base already on some apps with Android 1.5 set as the minimum version. I want to update the apps to take advantage of some of the newer features offered in Android 2.0 and greater. What is the best way forward so I don't break things for my current 1.5 and 1.6 users?
If I simply update the application with a new min SDK version, will 1.5 and 1.6 users be prompted to uninstall? Or will they just not see the update? What about future development that I want to apply for everyone, say a bugfix. Will I have painted myself into a corner? Another solution would be to fork and create a new app for 2.0 users, but that is undesirable for several reasons.
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Jun 23, 2010
I have had my Desire no for almost 2 months, and like most I have tried installing and uninstalling many apps, to see what I like.Due to doing a factory reset on my phone yesterday I have layered back all the apps I was using and have noticed that I have used considerably less memory than before, making me very suspicious of the uninstall method used within the market place.Does it leave behind pieces of the app, and if so what's the cleanest method of uninstalling apps.
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Dec 4, 2009
I've been scouring the web looking for information on setting up a peer-to-peer connection between Android handsets and so far have drawn a blank. The only thing I can definitively seem to work out is that it was made a whole lot more difficult when XMPP was removed from 1.0. Apart from that, I find a couple of threads on an OpenIntents board about porting an XMPP implementation to Android that were last posted nearly 2 years ago. Has anybody solved this problem effectively? What's the best way of doing it (from a games point of view)?
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Sep 17, 2009
I'm writing an application where real-time knowledge of the GPS state is critical to convey to the user. I request GPS updates at 1000 ms intervals -- when I haven't received another update 1500 ms past the most recent update, I want to display a yellow icon, and 5000 ms after the most recent update I want to display a red icon. Currently, I'm doing it like this: private CountDownTimer gpstimeout; public void onLocationChanged(Location location) { if (gpstimeout != null) gpstimeout.cancel(); gpstimeout = new CountDownTimer(5000, 1500) { public void onTick(long m) { setYellow(); } public void onFinish() { setRed(); } }; gpstimeout.start(); }
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Mar 22, 2010
What is considered "best practice" when executing queries on a SQLite db within an Android app? Is it safe to run inserts, deletes and select queries from an AsyncTask's doInBackground ? Or should I use the UI Thread? I suppose that db queries can be "heavy" and should not use the UI thread as it can lock up the app - resulting in an ANR. If I have several AsyncTasks, should they share a connection or should they open a connection each?
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Sep 29, 2010
I'm new to developing Android applications, and have only a little experience with Java in school. I was redirected to StackOverflow from the Google groups page when I was looking for the Android Beginners group. I have a question about what is best practice to pull content from a web source and parse it. Firstly, I would eventually like to have my application threaded (by use of Handler?), however, my issue now is that the class I have created (Server) to connect and fetch content often fails to retrieve the content, which causes my JSON parser class (JSONParser) to fail, and my View to display nothing. After navigating to the previous Activity, and attempting to call the connect(), fetch(), and parse() methods on the same remote URI, it will work. Why does this (sometimes retrieve the remote data) happen sometimes, but not always? What is the best practice, including the use of ProgressDialog and the internal Handler class, to make my application seemless to the user. Is this the best place to ask this question?
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Sep 22, 2009
I am creating a database driven app for managing people. I am showing a list of people with each name in a TextView. When a TextView is clicked, I launch a new intent to show the detail for the person. My question: What's the best practices for passing the id of the person to the new intent? The TextView is displaying the name of the person, so how do I know the id of the person? Once I know the id, I know how to pass it to the new intent, but I don't know what the best way to associate the id of the person to the TextView. Is there a best practice for this?
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Aug 16, 2010
In general, I'm very impressed with Android's default text to speech engine (i.e., com.svox.pico). As expected, it mispronounces some words (as do I) and it therefore occasionally needs some pronunciation guidance. So I'm wondering about best practices for phonetically spelling out those words that the pico TTS engine mispronounces. For example, the correct pronunciation of the bird Chachalaca is CHAH-chah-LAH-kah. Here is what the TTS engine produces: mTts.speak("Chachalaca", TextToSpeech.QUEUE_ADD, null); // output: chuh-KAL-uh-KUH mTts.speak("CHAH-chah-LAH-kah", TextToSpeech.QUEUE_ADD, null); // output: CHAH-chah-EL-AY-AYCH-dash-kuh mTts.speak("CHAHchahLAHkah", TextToSpeech.QUEUE_ADD, null); // output: CHA-chah-LAH-ka mTts.speak("CHAH chah LOCKah", TextToSpeech.QUEUE_ADD, null); // output: CHAH-chah-LAH-kah Here are my questions. Is there a standard phonetic spelling recognized by the Android TTS engine? If not, are there some general rules for making custom pronunciation spellings that will make the spellings more likely to be correct in future TTS engines/versions? It appears that the Android TTS engine ignores text case. What is the best way to specify emphasis?
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Apr 8, 2010
I am still learning bu find Android the cool platform for allot of useful applications. I have written a Service for doing GPS tracking and it consists of a Service and a Control activity to manage, monitor and configure the service. I am looking for the preferred way for the Control Activity to define settings for the Service, things like IP address and Update interval. I envision something like a Registry on windows where these settings can be shares and updated.
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Jun 16, 2009
I am quite new to Android and Java. Before I was working with C++ where the events where dispatched with messages. Now I would like to create the same user experience for Android platform and I would appreciate any of your suggestions or comments on what is the best way to bind events to user controls.
Here is an example from C++:
ON_MESSAGE(WM_RECORD_START, &CMainFrame::OnRecordStart)//Method OnRecordStarts() executes on WM_RECORD_START_MESSAGE...................
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Oct 6, 2010
Some of my app's preferences could use some more explanation than the scarce space available for the summary. Sadly, there doesn't seem to be support from the system, like an optional help button that shows a longer text. How do you solve this problem? The first thing that comes to mind is an additional custom "preference" like "more information to above entry" that opens an AlertDialog with the help text, but that's not really nice for both user (two entries for the same preference) and the developer (manual work to do in Preference Activity). A bit nicer for the user, but way more work for the developer would be custom dialogs for each preference with more text and/or a help button. Is there a better solution or even an officially recommended best practice?
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Apr 19, 2009
What is the best way to release two versions of an application? E.g. a free version with limited features, and a paid version with the full feature set. #ifdef would be the ideal way to do this, but Java doesn't support it. Could I do something like: try {import com.foo.myapplication.ExtraFeatures; } catch (Exception e) { // ignore it, this must be the free version}? I could manage with this kind of construct, although #ifdef really would be ideal.
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Jul 29, 2009
I didn't use much Java before Android so my knowledge concerning the gc is marginal. Now I'm developing a highly physics-based game and therefore I need to do many calculations each time step and many (25) time steps per second. At the moment I'm almost only using local objects (float) in my methods, so I guess they are allocated every time the method is called (which might be, for example, 25*100 = 2500 times a second , for 100 objects with calculations on them). This causes massive activity of the garbage collector like freeing ~10000 objects every 1-2 seconds (taking ~200ms on a real device). Now I really want to optimize that because even there's no noticeable delay due to the GC (and the frame rate is constant), this seems just not well. But I read on many documentations concerning Java optimization, that there is not much to optimize in modern versions of (desktop) Java, because the GC is fast enough. Does this apply to Android, too? Does the compiler optimize anything like frequently, steady allocated objects (like floats)? What would be best practice: keep all local objects and allocate and free them all the time or use class-global objects, even if they are only used inside one particular method (which is bad programming style but conserves GC?
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Jan 13, 2010
If I want to render just a huge map, what is the best practice when using OpenGL ES with a mobile device (Android or iPhone based)? What is the best structure to contain all the vertices, normales and texture coordinates? I guess using a interleaved structure may give you some performance benefits caused by memory caching. Ok? Should I use drawArrays or drawElements to push my data to OpenGL ES? Well, I did no testing at all but I might think, that drawElements might be faster if the GFX does not use shared memory since you do not have to push that much data. Since this is really close to metall, what do you think? (the iPhone is ARM based while the Android platform is Qualcomm based (also an ARM?)
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May 23, 2010
I'm embarking on a GUI Activity composed of a viewflipper, which I would like to contain 10 linearlayout layouts. Is it advisable to put all of my layouts into the same XML resource/layout file? If not, is there a more organized approach to coding a viewflipper with many layouts? Will having everything in the same file come at a significant performance cost?
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Mar 9, 2010
I'm having troubles with users that report that if they leave the application opened and after a few hours when they return to it the app crashes. I'm pretty sure it is because I'm not storing/restoring the status correctly when my process is killed by the system, but I would like to be able to test it in a repeatable way. Which is the best way to simulate the same behavior that happens when Android kills my process on low memory conditions?
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Apr 11, 2009
I am trying to display a high score table in my application and wanted to know the Best Practice for displaying static headers or footers. The data for the High Score tableis a REST web service returing up to 100 JSON records. I have looked at some of the previous posts http://groups.google.com/group/android-developers/browse_thread/threa. that talk about addHeaderView() & addFooterView() but they all seem to indicate that the footer or header will scroll off the screen. My 1st question is has someone been able to implement this in a clean way to allow a basic static header or footer. My second question is is their another way I could accomplish my goal of displaying my high score table besides a List View. I will be displaying 6 columns of data which will need to scroll vertically.
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Jul 18, 2010
When i have a broadcastReceiver say android.intent.action.MEDIA_BUTTON and i want to update the current activity's UI without creating a new activity, is there any good practice on this one?
What i know (might not be correct)
1) I can put the BroadcastReceiver in the same class as the activity and call the updateUI function after certain activity
2) Create a ContentObserver?
3) Communicate to a service created by the activity, use aidl. (I dont know how to get the current service if its registered from an activity)
4) Create a custom filter on the broadcastReceiver located on the same class as the activity, and use context.sendBroadcast(msg of custom filter) and in the custom filter call updateUI (same as one but more generic?)
The final flow is it would come from a BroadcastReceiver and ends up updating the UI without renewing the activity (unless the activity is dead?)
Kindly provide links/source code on your how you tackle this kind of problem.
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