Android :: Util.SparseArray Space Time Complexity Properties
May 19, 2009
I need a map from int to certain objects. I wanted to use the HashMap, but in the documentation of SparseArray it says that SparseArray is intented to be *more efficient*: http://developer.android.com/reference/android/util/SparseArray.html
However i think the documentation is not entirely correct and needs more info: When reviewing the sourcecode of SparseArray and comparing it with the HashMap i come to the following conclusion
Source code of Sparse Array: [url]
For SpareArray: Time complexity for reads and writes on a map of size N is log2(N) + 1,
However the time complexity for a HashMap of size N is C*N (where C is a constant) (according to the javadoc [url]
So maybe SparseArray is more efficient with respect to space complexity it is not for time complexity. So for programs that need high performance a HashMap may be better.
At least thats what i think. Am i right? Am i wrong? I need a very fast implementation for my game.
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Jul 29, 2009
I want to make calendar view in order to support touch interaction. So I'd like to build new custom calendar view. I tried to make mapping function between view offset and real date value.
Here is my idea:
If I can compute the number of weeks since base date(in my case, 1989-12-31), it is easy to know offset. HEIGHT_FOR_WEEK * NUM_OF_WEEK is very simple computation to know exact offset.
My problem is this:
First I got milliseconds value from base date. And I set the milliseconds to another calendar object. I expected same date from that object. But actually it was different date.
CODE:...............
Here is my CODE:.........................
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Oct 26, 2010
Which one should I use java.util.Date or android.text.format.Time? It seems you can accomplish what one needs to do with either. What I need to do is at times get the current date and time and sometimes set a date and time specified by the user.
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Nov 12, 2010
I'm creating a android.text.format.Time Object from a java.util.Calendar Instance, and I read it out field by field.
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Jun 18, 2010
IS there a way to keep the phone from ringing constantly without a break betweens rings?
I pick a nice quiet little ringer but when my phone rings its so annoying because its like "RingRingRingRing" instead of "Ring..................Ring".
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Nov 3, 2009
Space STG - Galactic Wars (real-time strategy) - introduction I want to introduce my game. If You would like to see more, please visit www.inventiventure.tk. Space STG - Galactic Wars is real-time space strategy game. Build buildings, economies, ships, defense and technology. Send your fleets of ships to conquer enemy planets. Use nuclear missiles, probes, planetary defenses, cloaking technology and more. The aim of Space STG is to dominate the Galaxy. Expand your empire by mining resources, building space fleets and planetary defenses. Invade your enemies planets and size control of each region.
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Oct 6, 2010
I have purchaced new sony ericson X10 recently. Can some one suggest me how to remove time space from my desktop. Its covering my photo in desktop. Also tell me me how to disconnect/silent the phone when i get a call.
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Jul 30, 2010
I have always been a little uncomfortable with the HTC widget on the home screen that took a large 2x4 block (2 rows x 4 columns) out of the home screen to display the time and weather.. especially because I wanted a few more apps to be displayed on my home screen that I regularly use..
So I removed the HTC clock widget that displayed the large 4x4 clock and weather and instead dropped the HTC clock widget that is 1x2 (5 of the 12 choices available in that widget).. and the HTC weather widget right next to it (or even below it).. which is also a 1x2 size..(choice 3 of 3 in that widget)..
so I basically get the same information with regards to time and weather..and I also end up saving 1 row, which can be filled with 4 additional apps.
Another tip: Instead of using the HTC favorites widget to peg your favorite people to call a touch away.. use the shortcut/add person to peg them on screen. The favorite widget takes a lot more space especially when you don't fill it up.
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Aug 12, 2010
I just downloaded this Android System Information free from teh Market, and I thought I'd let you guys know about it. It's pretty damn awesome. It basically tells you everything you wanna know about your phone including every spec, every task running and how much CPU it is eaiting in real time, it has logs and everything. I highly recommend getting this app.
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Sep 3, 2010
I want to know about the util Class used in Java. I am currently working on one Application in Android where I need to used a class from one file to another different file. I was told to import it like "import com.android.utli.(ClassName)" here the "com.android.util" is a package name.
Can I use thast class in my another file simply by importing the package along with the Class Name?
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Jan 15, 2010
Can I rely on Timer and TimerTask to work properly on Android?
I have a background Service with a single Timer, and I schedule (possibly multiple) TimerTask's via Timer.schedule()
At the beginning of each implemented TimerTask.run() method, I check the TimerTask.scheduledExecutionTime() and compare it with the current time. Sometimes things are fine, and the difference is a small number of ms. But sometimes things are nowhere near fine, and the invocation of my TimerTask is *way* late -- like multiple hours late.
Can an Android phone go into some deep sleep mode when it doesn't think anything is going on that would cause a TimerTask to be so late? Can I not reliably use TimerTask for scheduling events, and should I be using some Android-specific means (e.g. the AlarmManager, or a Handler) instead?
I have not found anything that says that java.util.TimerTask shouldn't be sufficient, the Android docs include no kinds of qualifiers, and this post (from Mark Murphy, who's written several good Android books) specifically mentions it as being available:
http://groups.google.com/group/android-developers/browse_thread/threa...
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Jan 22, 2010
I want to create a java.util.map in android from a resource. I want to do this because I have a lot of entries to populate into the java.util.map and I want to store the values in the res folder of the project in xml format.
Is there an effecient way to do this in android? My map will have around 2500 entries so I want to do this as effeciently as possible and I don't want to hard code them...
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Apr 14, 2010
I want to use ConcurrentLinkedQueue in an android application, have written the code, but now I'm getting an error when the project builds:
Conversion to Dalvik format failed with error 2
I'm using Eclipse with the lastest version of the ADT plugin.
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Apr 19, 2010
That is the only thing I can think of. When I generate a random number (for the radius of a ball), after a while, the radius goes to one number and sticks that way. I've even tried setting the random number value to 0 before getting the random number, and java.util.Random must be at fault, it still gives the same random number. Here is an apk if you would like to try it yourself: http://74.118.194.50:84/Balls.apk
Here is a snippet of the code (I would rather not release the full source): <code> Random randomizer = new Random(System.currentTimeMillis()); int hw; hw = randomizer.nextInt(95-15+1)+15; </code>
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Mar 15, 2010
In a Android application I want to use Scanner class to read a list of floats from a text file (it's a list of vertex coordinates for OpenGL). Exact code is:
CODE:.................
It seems however that this is incredibly slow (it took 30 minutes to read 10,000 floats!) - as tested on the 2.1 emulator. What's going on?
I don't remember Scanner to be that slow when I used it on the PC (truth be told I never read more than 100 values before). Or is it something else, like reading from an asset input stream?
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Sep 25, 2009
My app needs to save its state before being killed, and since that state is really small (one Long), I've decided to use java.util.Preferences. I use it like the way I would be using in any Java application (and never had problems), though I am not sure this is the correct way here on Android platform: private static final Preferences prefs = Preferences.userNodeForPackage (WordChoice.class);
I update preferences in onPause() method, to ensure that data is always persisted no matter how my app ends: Here is that fragment of code: protected void onPause() { super.onPause(); prefs.putLong("currIndex", somePositiveValue); }
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Apr 7, 2010
I'm trying to launch a lot of remote connection retrieve picture on a server. To do this, I use AsyncTask.
This pics are displayed in a listview using adapter.
If I implement this in my adapter, images are retrieved but the display is bad (problem with index or something like that).
If I try to retrieve image when I build my object list (contained in my listview), I get the exception 04-07 13:35:57.744: ERROR/AndroidRuntime(4132):
CODE:.................
What is this exception ? Why I can launch multiple asynctask in my listview (giving to me a bad result) and not in a simple object without having this issue ?
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Aug 10, 2010
I'm developing an application and I want to use android.text.util.Regex.WEB_URL_PATTERN as the pattern for the Linkify. But, as I have notice, I cannot import android.text.util.Regex for some reason.
Why so? Is there a way to workaround this?
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Jun 23, 2010
Considering writing a wifi cracking (wep, wpa) auditing tool for the android platform, but I am wondering if it is possible to do without a rooted phone.
I had thought it would be impossible to run on an unrooted phone due to the phones wifi chip ignoring packets not addressed to the phone. That is, without the ability to set the wifi chip to monitor mode many of these attacks wont work. I was surprised to learn that android supports multicast packets. That is, android phones can be set to receive packets not addressed to them.
My questions are: Does having a multicast lock mean I can receive all packets broadcast, or does it only apply to packets with a multicast flag (if such a thing exists)?
Is there a difference between monitor mode and multicast? Does the android api have a system for switching channels?
More generally I'm curious: Is anyone familar with other wifi cracking projects running on android (google searches turned up very little)?
What difficulties am I likely to run into?
This question is related to SO question Is there anyway to put Android WIFI (droid handset) into permiscuous monitoring mode?
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Mar 18, 2010
I've done changes in an Android native library and installed a new system.img file but am now getting an unrelated Error on startup. I can get past it by swallowing the error but I wanted to know if anyone can explain what the issue is.
The Android implementation of Logger.java claims that it is Forcing the LogManager to be initialized since its class init code performs necessary one-time setup. But this forced initialization results in a NoClassDefFoundError. I'm thinking that it has something to do with the class not having been preloaded by Zygote yet but am not that familiar with the whole class loaders and VM business.
code:....................
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Oct 27, 2009
I am using the Eclipse plugin and I have the above error. I know why it is occurring, it is because I want to override a class file in one of my imported jar files. I am including a new Util class before the jar file in question. I have tried it both as a simple .class file in my package hierarchy and I have tried putting it into another jar file and including it before the one to be overridden.
I would like it to behave like the Java classpath and use the first one it comes to when running through all the classes. I don't mind if dex wants to give me a warning that it is not using the second Util.class file but it should let me build my application. To build my app, I have to create a special jar file without the old Util.class in it. This is annoying as I would like to use the bog standard version so that others can use it with ease too.
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Feb 8, 2010
I'm building using Ant and trying to use build.properties to override some default values, and failing miserably. What am I missing?
Here's what I've tried:
1) Create a project with: > android create project --target 1 --name MyAndroidApp --path ./MyAndroidAppProject --activity MyAndroidAppActivity --package com.example.myandroid
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May 13, 2010
How to get the dirty(changed) properties(any controls subclasses of view) amongst a number of properties on a layout. Does android has a dirty flag to mark if the layout has any field that has a changed content?
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Jul 8, 2010
How can I make my own UI defining my properties?
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Aug 19, 2010
I'm creating an currency exchange rate application to learn Android. The app will list all exchange rate in a list, each of them has the layout like this (in essential) code...
To list exchange rate for all currencies I have the following approach:
- Design the layout for one currency (let's choose EUR as first currency)
- Generate the layout for all other currencies automatically by:
1. Copy all properties of the EUR-layout into the new currency layout
2. Modify some properties of new currency layout like: ID, Rates ...
3. Repeat steps 1,2 for all sub-layout of the new currency layout
But I don't know how to code step 1, so I did a lot of google about: "android copy view" "android copy properties" "android copy view" "android clone view" "java clone object" .... but still no solution.
So, my question is: how to copy all properties of a view ?
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Feb 18, 2010
When I import a new existing project into Eclipse, I get the following error message when attempting to execute as an Android project..
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Sep 9, 2010
i got this notification yesterday so i deleted some apps and all my text messages but i cant get rid of it now!
any ideas?
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Apr 2, 2010
In an Android app I have a utility class that I use to parse strings for 2 regEx's. I compile the 2 patterns in a static initializer so they only get compiled once, then activities can use the parsing methods statically.
This works fine except that the first time the class is accessed and loaded, and the static initializer compiles the pattern, the UI hangs for close to a MINUTE while it compiles the pattern! After the first time, it flies on all subsequent calls to parseString().
My regEx that I am using is rather large - 847 characters, but in a normal java webapp this is lightning fast. I am testing this so far only in the emulator with a 1.5 AVD.
Could this just be an emulator issue or is there some other reason that this pattern is taking so long to compile?
CODE:.......................
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Jan 20, 2009
I am modifying the Settings application, and needing to access the system properties. By using android.os.SystemProperties.get, I can read the system properties. However, I can not set the system properties back with android.os.SystemProperties.set. This function has no return and the system properties never get changed. Why? Is there any permission required?
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Jul 29, 2009
I'm using BaseExpandableListAdapter, and there is a drop-down button (looks like an arrow) on the left side for each parent item to indicate that you can expand that item to view child items. The question is: How can I change the properties of that drop-down button such as its position? I basically want to move it a bit lower in each parent item.
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