Android :: Java.util.Random Caching
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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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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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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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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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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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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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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Jul 28, 2009
Im currently developing a system where the user will end up having large arrays( using android). However the JVM memory is at risk of running out, so in order to prevent this I was thinking of creating a temporary database and store the data in there. However, one of the concerns that comes to me is the SDcard limited by read and write. Also another problem that comes to mind is the overhead of such an operation. Can anyone clear up my concerns, as well as also suggest a possibly good alternative to handling large arrays ( in the end these arrays will be uploaded to a website by writing a csv file and uploading it).
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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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Apr 24, 2009
I've got a activity showing the user a list of songs to play, and when he opens a song I launch an activity which embed a player.
My problem is that when i finish playing i call "this.finish()", but when the user reopen the player, the "onCreate" is launched and it seems that the GUI is building itself "again".
I've tried to not call "this.finish()" and call the Activity.startActivity on the father, but with this way, when I clic on the "back" button on the emulator, I get all the players playing in the same time (they still exist).
So my question, is there a way to make an activity "a singleton" or to freeze it to be retrieved later (It can't be able to retrieve it with "back" button) or a way to cache all the constructions so to not have to do it again ?
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Nov 5, 2010
My app makes several calls to getFromLocationName from the android.location.Geocoder; class, this is currently handled in my activity which also displays some data depedant on the results of that call.
This can be quite slow, for example before the activity can load it first has to complete the various calls, and that is reliant on a network connection.
Once I have the results, I don't really need to refresh that (I mean how often do locations and geo coordinates change?)
My question : How can I best avoid having to query for this data each time my app runs. Should I do something with a service that loads them all on startup? (could be quite slow if it has to query 50+ times). OR should I make the call, store results in SQL, then only query next time if I don't currently hold the results?
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Feb 2, 2009
I am performing hundreds of calls to a single content provider to perform various insertions, updates and deletions. After profiling my application, I have noticed that the ContentResolver class takes approx. 30ms to retrieve the corresponding content provider object for each call. Is there anyway to retrieve a reference to the content provider rather then going through the ContentResolver every time?
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Apr 27, 2010
I am retrieving a list of images and text from a web service.The images are getting displayed in the list view. But the problem is, when i scroll down the list the entire images are getting loaded once again. When i scroll twice or thrice there is a OutofMemory occuring.Can anyone tell me how to cache the images and also to avoid the loading of the images that are already loaded when i scroll down. I have tried to increase inSampleSize but it didnt work.
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Nov 24, 2008
I don't currently have a data plan. Since I'm on WiFi 95% of the time, I don't plan on getting one. The only thing I haven't been able to do easily (without a data plan) is use Google Maps while driving/walking.If I load the maps before leaving a WiFi hotspot, my location is tracked and I can pan around the map. Of course, as soon as I want to view another uncached portion of the map, I can't.Maps are small, and it would be perfect if I could cache maps for a certain area - say everything within 100 mi of my house. Any ideas?
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May 6, 2010
I am trying to cache my viewgroup to a bitmap and blit this to screen instead of calling dispatchDraw on the group while scrolling for performance reasons. This works quite well on 1.5, but has ugly scaling artefacts on 1.6 and newer for high density screens. Because of my 1.5 compatibility I can't find a way to set the density of my cached bitmap.
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Jun 16, 2010
I've had my Incredible since 4/28, and everything has been working smoothly up until about last Thursday night when it just restarted out of the blue while I was listening to music. Then right after it booted up, it restarted again, then again about seven more times. I got fed up and took out the SD card and it seemed to stop after that, so I haven't put the SD card back in since then.
Just now, Wednesday, about a week later, I was browsing around on the internet and all of a sudden, it restarted, and then again, and again, and again. I've read that it is because of poor signal strength or something like that so I had just enough time to put it in airplane mode before it restarted again.
Side note, that theory about it being caused by poor signal seems to make sense because the first time it happened to me I was out of town in a city that gets very bad coverage with Verizon, and now today when it started happening again was at my house where for some reason I get very bad service with the incredible, my old phone worked perfectly fine in my house but the incredible gets terrible service, and so does my brother's Droid. In fact, about two weeks ago I got my first dropped call on Verizon in about three years, and it was in my house.
So anyways, I decided to put it in airplane mode, and just after I put it in airplane mode it restarted again. Then when it booted back up my Helix Launcher 2 home screen went back to the standard Helix Launcher 2 icons, I go into my messages and everything is gone, my contacts are all gone, everything is gone. I go to the app menu and all my apps are still there, but when I start up an app, all the custom settings are default now. I went into the settings and my accounts are all still there. I click on internet and I get a terms of service agreement, it's as if I am booting it up for the first time, but for some reason my apps and accounts are all still there.
I turn airplane mode off thinking it might have something to do with it not being connected to my google account, and I restart it again and everything is still gone. I don't know what to do, has this happened to anyone before? I feel like there should be a way for me to get this stuff back since my apps are still there and my accounts are still synced, but random things are missing like my contacts and messages etc. This is really starting to get annoying, I have insurance and everything, but I really don't want to exchange it for another one because I've read that other people who have had there phones replaced have still had the same rebooting problem, even after going through multiple replacements.
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Jan 14, 2014
I'm trying to employ HttpResponseCache to cache each HTTP-request sent with HttpURLConnection.
why I get hit count always zero?
Code:
HttpResponseCache.getInstalled().getHitCount()
Usage:
Code:
for(int i = 0; i < 2; i++){
try {
HttpURLConnection connection = (HttpURLConnection) new URL("http://www.google.com").openConnection();
connection.setUseCaches(true);
if(i == 1){
try {
[code]....
On 2'nd run I have "NOT cached" in console and hit count == 0.
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Jul 25, 2010
I really like the new Google Navigation, and it would be really handy for when I go abroad cycling, apart from the roaming charges. Any apps that can cashe the maps and store them, or must I always be connected?
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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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Nov 9, 2010
Opera Mobile 10.1 Beta Brings Turbo-Powered Browsing to Android.This is supposedly different than what's in the market.This forum is stale lately, so let's mix it up.I still like XScope, but Firefox is promising, and though I have NEVER been a fan of Opera, I am gonna try it.The one touch pinch zoom on Xscope is really tough to give up
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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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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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Jun 15, 2010
I noticed this same issue with my HTC Hero, and then it seemed to go away. Now I've noticed it again.
The issue is this: I have around 2700 songs on my SD card, all in a folder called Music, and they are arranged, quite logically, by artist and album under that. Unfortunately, when I put the music application on random, it seems to get stuck on 4 or 5 artists (and sometimes within those artists, one particular album) and play those almost exclusively, with only an occasional diversion to some other artist. At one point it was so bad that a. it played one particular song 6 times in a 4 hour period, and b. I got so tired of one of my artists, I deleted it entirely!
So, is this a bug with the built in music player? Is it because of the amount of music I have? Is it because of where my music is stored? Has anyone else had this problem? (Or does Android OS just have an affinity for The Byrds? )
Are there any other music apps I can try? I tried Simply Music, and it did work much better on the randomization, but it hung for a few seconds several times (for no discernable reason) and it is very slow to load.
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May 19, 2010
i have two files
App.java
Gallery.java
App. java contains frontend buttons and functionalities Gallery.java lists the imagesin the sd card. i want to call Gallery.java in click event in app.java
App.java
package gallery.display;
import android.app.Activity;
import android.os.Bundle;
import android.view.View.OnClickListener;
import android.view.View;...........
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