Android :: Caching Large Arrays To SQLite - Java / Android
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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Oct 10, 2010
I recently created a program that gets medi-large amounts of xml data and converts it into arrays of Strings, then displays the data.The program works great, but it freezes when it is making the arrays (for around 16 seconds depending on the size).Is there any way I can optimize my program (Alternatives to string arrays etc.)
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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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Apr 4, 2010
I simply need to add floatArray1 to floatArray2 storing the result in floatArray2.. no third array. all arrays are one dimensional but are very large. probibly as large as the os will let me get away with. Max i would need is two float arrays with 40,000 floats each. but i could get away with 1/10th that i suppose minimum.Would love to do this in 1/30th or 1/60th of a second but that does not seem possible? Also if the code is JNI,NDK or OpenGL ES thats fine. does android have an assembly language or like machine code i could use somehow?
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May 5, 2010
How to create arrays of class instances in JAVA. code...
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Dec 13, 2009
Does anybody know of a work around for the android xml file string array inability to process string <item>'s that are not legal java variable names If not, is this not a major bug? Why does an item in an array need to generate a reference id anyway? Isn't this redundant?
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Jul 26, 2010
I will be developing a dictionary app for both Android and iPhone. The data will be embedded within the app, and it consists out of approximately 100000 words, with genus and plural form. Is it better to use a SQLite database or can I just stick to XML? Somehow SQLite sounds more efficient, but I thought let's just ask.
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Sep 2, 2009
I need to insert approximately one million rows of data (spread over 4 tables) - each row has one or two numeric fields, and two or three text fields (normally quite short). Single-column indexes on all the fields. After doing some tests on the emulator with a small test set, I extrapolated (assuming the last row will be inserted with a similar speed to the first row) my results to figure out that this would take about 15 hours (I have a Core 2 Duo running Vista). However, then I tried running the small test set on my Hero and I was surprised to see it run more than four times faster. I would guess it would take about 3 hours on the Hero. Alternatively, I could make the pre-populated database available as a download on the first run but this is likely to be a 120MB download. I have a few questions I'm hoping someone can help me with: 1. SQLite performance on the actual device being 4-5 times faster compared to the emulator - is this normal/expected? 2. Do the figures above generally sound fast/slow/normal (sorry this is so vague)? 3. From a user perspective - would it be best to provide a 120MB download or a 3 hour "first-time initialisation" step (plus 6MB download)?
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Jun 26, 2010
I will be making a mobile application in Android. My application is like Google Map's Get Direction feature, but a lot more complex, so I need to store data about points in the map. So I'm worried that SQLite may not be able to handle these large amount of data(or considering the limited storage of the phone). I have no background in SQLite so please bear with me.
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Jun 30, 2009
I have a large(ish) database - around 30MB, created offline with 400,000 rows. Doing a simple select (name LIKE pattern%) and then showing the query in a listview takes about 10 seconds. I tried indexing that field but no difference. If this is normal I will just use a raw data file and do a binary search myself. If this is not normal I hope someone has a hint or two to what might be wrong.
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Oct 23, 2009
I am facing a problem in my Android app which is calling native functions through JNI. So thought somebody in this group can help me to resolve this. The current code :
1. Create an array in JNI layer ( by NewIntArray()) which can be used by both Java & C.
2.we can name that array as type jintArray array.
3.We call GetIntArrayElements() on this array to get its elements i.e, int * elementsX.
4. This elements would be used by a native call which will set it to some value.(project specific* : may not need interest for this issue)
5. We now get the updated value of elements. And copy it back to array using ReleaseIntArrayElements()
6.We use array in bitmap/canvas class of Java layer to display on screen. The whole procedure is followed for (480x640) times. And so there is a redundant creation of the array for every frame display. Is there any way to avoid this creation of array for each frame. Any better solution to achieve the above? I am not getting a way out of this & the performance of my app has gotten very low too Any JNI code snippets to modify steps (1 to 3 & 5) would be of great help to me.
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May 28, 2010
I guess many people already read this article:
Using your own SQLite database in Android applications: http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/comment-page-2/#comment-12368
However it's keep bringing IOException at
CODE:.............
I'am trying to use a large DB file. It's as big as >8MB. I built it using sqlite3 in Mac OS X, inserted UTF-8 encoded strings (for I am using Korean), added android_meta table with ko_KR as locale, as instructed above.
However, When I debug, it keeps showing IOException at
CODE:..............
I suspect it's caused by trying to read a big file. If not, I have no clue why.
I tested the same code using much smaller text file, and it worked fine.
Can anyone help me out on this? I've searched many places, but no place gave me the clear answer, or good solution. Good meaning efficient or easy.
I will try use BufferedInput(Output)Stream, but if the simpler one cannot work, I don't think this will work either.
Can anyone explain the fundamental limits in file input/output in Android, and the right way around it, possibly?
WITH MORE DETAIL:
CODE:...............
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Oct 28, 2009
I want to get an array of strings reading from arrays.xml file we add in android values/ folder. Could any one kindly give a solution for this. Otherwise I will have to input each these entries in strings.xml and take them to java code using getResources()getString()
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Oct 7, 2010
Presently am displaying html file in web view and my emulator size 1024*600. If the html file is large then user is scrolling down to see bottom part of the html. I Need to break these html file in equal parts so that it fits exactly in my screen size. I don't want User to Scroll Down but load remaining part (next page) next time.
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May 30, 2010
when i download large data from website, i got this error information:
I/global (20094): Default buffer size used in BufferedInputStream constructor.
It would be better to be explicit if an 8k buffer is required.
D/dalvikvm(20094): GC freed 6153 objects / 3650840 bytes in 335ms
I/dalvikvm-heap(20094): Forcing collection of SoftReferences for 3599051-byte al
location
D/dalvikvm(20094): GC freed 320 objects / 11400 bytes in 144ms
E/dalvikvm-heap(20094): Out of memory on a 3599051-byte allocation.
I/dalvikvm(20094): "Thread-9" prio=5 tid=17 RUNNABLE
I/dalvikvm(20094): | group="main" sCount=0 dsCount=0 s=0 obj=0x439b9480
I/dalvikvm(20094): | sysTid=25762 nice=0 sched=0/0 handle=4065496
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Jul 14, 2009
I have had to program some applications that require large amounts of timed tasks to occur. However, I'm afraid to create so many timers because I haven't been able to figure out how they are handled by Java. Is there a problem with starting large quantities of scheduled tasks? If so, what is the better alternative?
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Aug 18, 2010
I have an minor issue when taking a photo. I have a button that invokes the camera, successfully takes a photo, and returns to my entry form. My only problem is the database leak that occurs when pressing the button to call the camera.
My code looks a little something like this.
code:..........
I run :
code:..........
In the onCreate of the Activity or Class that I am calling the camera in. I have not coded in mDbHelper.close(); anywhere not sure if i should when or where. I think i would rather just leave it open while capturing one image.
Logcat:
code:............
Everything seems to be working fine, but i would defiantly like to avoid any issues amongst the many android devices out there.
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Oct 23, 2009
I want make it support multiple screens(small,normal and large).I am 100% sure the all of layouts are working perfectly now, but large screen,the problem is that all XML files of layouts in layout-large can't load,The platform always load default XML file(these are under layout folder) at large screen environment.
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Jul 14, 2010
I created a sql lite database with the following columns:
static final String dbName="demoDB";
static final String tableName="Employees";
static final String colID="EmployeeID";
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("CREATE TABLE "+tableName+" ("+colID+" INTEGER PRIMARY KEY AUTOINCREMENT, "+
colName+" TEXT, "+colAge+" Integer);");
I want to select all the records in the database like this and display them in a gridview:SQLiteDatabase db=this.getWritableDatabase();Cursor cur= db.rawQuery("Select "+colName+", "+colAge+" from "+tableName, new String [] {});String [] from=new String []{DatabaseHelper.colName,DatabaseHelper.colAge};
int [] to=new int [] {R.id.colName,R.id.colAge};
SimpleCursorAdapter sca=new SimpleCursorAdapter(this,R.layout.gridrow,c,from,to);
GridView grid=(GridView)findViewById(R.id.grid);
grid.setAdapter(sca);but i receive the following exception:java.lang.IllegalArgumentException: column '_id' does not exist.the db table does not have a column with name '_id'so what is wrong with this 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 10, 2010
Hey Can anyone tel me how to use arrays in Android.I need to add the numbers given by the user
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Sep 29, 2010
I am trying to create a information based application, I have 92 subjects, for these subjects I have 92 map locations and maybe as much as 400 url links. Currently I have created a class for each map location and a class for each url link, but this would mean I would have in excess of 500 classes, so what I want to do is split the subjects in four catergories ie. listview of about 23 in four tabs which I have done and create a class that gets the url based on the selection the use makes and do the same for the map locations.Do I need to put these in a xml using the id method and how do you call individual entries, i.e. would I need 500 Android:id is there an easier way?
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Mar 16, 2010
I am just trying to display a list from an array that I have in my arrays.xml. When I try to run it in the emulator, I get a force close message. If I define the array in the java file (String[] testArray = "one","two","three","etc";) it works, but when I use "String[] testArray = getResources().getStringArray (R.array.testArray); " it doesnt work.Here is my Java file:package com.xtensivearts.episode.seven;
import android.app.ListActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;public class Episode7 extends ListActivity { String[] testArray = getResources().getStringArray(R.array.testArray); /** Called when the activity is first created. */
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Jul 22, 2009
Arrays.copyOfRange() is unavailable in Android, so I'm wondering what the preferred method of copying arrays is. Manually over a loop, or System.arraycopy()? Also, what was the reason behind the decision to not include Arrays.* ?
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Jan 1, 2010
I would like to create a list objects called Product (Listproducts).In the application I first have to create the list List products from XML file and then display the products on the map. One product can be located at several locations.Does anyone know what is the most appropriate way to create the structure (a list or linked list) which is the easiest to iterate through and enables to link the lists? The logic should work the following way:
1. Read each point from the list
2. Check which product belongs to the point
3. Display the product informations on the map
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