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How to avoid OutOfMemory Error / OOM (The Ugly Truth Revealed)

Wed, 05/26/2010 - 07:28 | by bence
SDK Version: 
M3

ERROR/dalvikvm-heap(4204): 691456-byte external allocation too large for this process.
01-25 22:13:18.694: ERROR/(4204): VM won't let us allocate 691456 bytes 01-25 22:13:18.694

If you have ever got the message above, you are at the right place.

First of all the reason:
Heap size != External Memory size
Dalvik's external memory is limited to ~ 4MBs for each process (That is the Ugly Truth). If it overflows, you get the BitmapFactory.DecodeFile Error.
That's why even if you have like 2MB-s heap memory free, VM won't let you allocate ~700KB.
Since you can't modify external memory's size, you have to reduce your memory usage. This is the only solution I have, but it really works at least.

The solution:
Let say you have a nice big Gallery with lots of large images. An ImageAdapter class will provide all of the images that you are going to use. Therefore you'll need a List of ImageViews.

How to have a default database

Mon, 05/17/2010 - 06:42 | by gabor
SDK Version: 
M3

If you want to include a database with initial data in your apk, you have to insert the database file into the projects assets folder, then programmatically check if the database, and if it does not exists copy the one from the assets.

You will need a function to check if the database exists, fox example:

  1. private static final String DATABASE_NAME = "testdatabase";
  2. private static final String DB_PATH = "/data/data/"+mContext.getPackageName()+"/databases/";
  3.  
  4. private boolean isDataBaseExist() {
  5.         File dbFile = new File(DB_PATH+DATABASE_NAME);
  6.         return dbFile.exists();
  7. }

If the check shows that the the database does not exist, a function like this will copy it:

  1. private void copyDataBase() throws IOException {
  2.         // Open your local db as the input stream
  3.         InputStream myInput = mContext.getAssets().open("databases/"+DATABASE_NAME);
  4.         // Path to the just created empty db
  5.         String outFileName = DB_PATH + DATABASE_NAME;

Connecting to MySQL database

Mon, 05/10/2010 - 01:58 | by gabor
SDK Version: 
M3
The most spread method to connect to a remote MySQL database from an android device, is to put some kind of service into the middle. Since MySQL is usually used together with PHP, the easiest and most obvious way to write a PHP script to manage the database and run this script using HTTP protocol from the android system. mysql logo

We can code the data in JSON format, between Android and PHP with the easy to use built in JSON functions in both languages.

I present some sample code, which selects data from a database depending on a given condition and creates a log message on the android side with the received data.

Lets suppose that we have a MySQL database named PeopleData, and a table int created, with the following SQL:

  1. CREATE TABLE `people` (
  2. `id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY ,

How to avoid OutOfMemory (OOM) Exception using Bitmaps (Solved)

Wed, 05/05/2010 - 02:19 | by bence
SDK Version: 
M3

Step 1.
First thing I want you to think about is that do You really need to use Bitmaps?
If the answer is No, go to step 2. :) Otherwise, think again.
Ok, Let me explain it. I needed Bitmaps to get the width of the images, to create an ImageAdapter for my Gallery. As far as I know, there's no other way to do that. So I used Bitmaps, and even if I recycled them, once in a while it stopped with the message: DDMS: OutOfMemory .. Phone: Force Close..
Not to speak about how laggy your app will be if you are using Bitmaps..
I've spent 2 weeks to find a solution for this problem, but I couldn't find any usable of them. Then I thought, I try not using Bitmaps anymore. So I have to find another way to get the width of images. Unfortunately, it's just a workaround, but it works so who cares, right?
I can determine widths with a PHP script, store it in my existing database. After I did that, everything was working properly.

Store images/files in database

Mon, 05/03/2010 - 08:19 | by gabor
SDK Version: 
M3

Hoever the practice is to store them normally and save the access route (Uri), sometimes it can be handy to store files/images completely in database.
In sqlite database there are only a few data types, so its easy to choose: files can be stored in a text as a ByteArray.

Lets see a sample code, where we download an image from the Internet then store it in the local database:

  1. //where we want to download it from
  2. URL url = new URL(IMAGE_URL);  //http://example.com/image.jpg
  3. //open the connection
  4. URLConnection ucon = url.openConnection();
  5. //buffer the download
  6. InputStream is = ucon.getInputStream();
  7. BufferedInputStream bis = new BufferedInputStream(is,128);
  8. ByteArrayBuffer baf = new ByteArrayBuffer(128);
  9. //get the bytes one by one
  10. int current = 0;
  11. while ((current = bis.read()) != -1) {
  12.         baf.append((byte) current);
  13. }
  14.  
  15. //store the data as a ByteArray
  16. //db is a SQLiteDatabase object
  17. ContentValues dataToInsert = new ContentValues();                          

Mastering Android Widget Development - Part5 - Final

Fri, 04/23/2010 - 07:15 | by gabor
SDK Version: 
M3

In this last part of the tutorial we will implement buttons to the appWidget, which will directly interact with the appWidget functionality.
We will have 2 buttons, a plus button to add one more day to the target date, and a minus button to decrease time left by one day.

First add the buttons to the countdownwidget.xml layout:

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <LinearLayout
  3.   xmlns:android="http://schemas.android.com/apk/res/android"
  4.   android:layout_width="wrap_content"
  5.   android:layout_height="wrap_content" android:orientation="vertical">
  6.  
  7. <TextView android:id="@+id/TextView01" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Time left"></TextView>
  8. <LinearLayout android:id="@+id/LinearLayout01"; android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal">

Mastering Android Widget Development - Part4

Fri, 04/16/2010 - 03:07 | by gabor
SDK Version: 
M3

As described in the previous part, we will use a Service to update the appWidget.
So we will have the Service below, which gets the command (right now we have only the update command), ant the appwidgetId, reads the date from sharedPreferences and updates the widget.

  1. package com.helloandroid.countdownexample;
  2.  
  3. import java.util.Date;
  4.  
  5. import android.app.Service;
  6. import android.appwidget.AppWidgetManager;
  7. import android.content.Intent;
  8. import android.content.SharedPreferences;
  9. import android.os.IBinder;
  10. import android.widget.RemoteViews;
  11.  
  12. public class CountdownService extends Service {
  13.         // command strings to send to service
  14.         public static final String UPDATE = "update";
  15.  
  16.         @Override
  17.         public void onStart(Intent intent, int startId) {
  18.                 //a command, to define what to do, will be important only in the next tutorial part, now there is only update command
  19.                 String command = intent.getAction();
  20.                 int appWidgetId = intent.getExtras().getInt(

Mastering Android Widget Development - Part2

Fri, 04/02/2010 - 07:32 | by gabor
SDK Version: 
M3

In Mastering Android Widget Development - Part1 we have gone trough the basics of appwidgets. Now we start to develop the example application, which couts time left to a given date.

First implement the configuration activity. It will contain a DatePicker, an OK button and a Cancel button, defined in the configuration.xml layout:

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <LinearLayout
  3.   xmlns:android="http://schemas.android.com/apk/res/android"
  4.   android:layout_width="wrap_content"
  5.   android:layout_height="wrap_content"
  6.   android:orientation="vertical">
  7.         <DatePicker android:layout_width="wrap_content"
  8.         android:layout_height="wrap_content"
  9.         android:id="@+id/DatePicker">
  10.         </DatePicker>
  11.        
  12.         <LinearLayout
  13.         android:id="@+id/LinearLayout01";
  14.         android:layout_width="wrap_content"
  15.         android:layout_height="wrap_content"
  16.         android:orientation="horizontal">
  17.        

How to download file/image from url to your device

Wed, 03/24/2010 - 08:41 | by jozsi
SDK Version: 
M3

We wrote a code for download image from a website to the phone. You can work with images (and files) in your applications, but this article may be useful for java developers too.

Debugging database

Fri, 03/12/2010 - 02:25 | by gabor
SDK Version: 
M3

When I first tried to manage an sqlite database on an android device I was not sure about where I fail in it. Can I even insert the records into the database, or I fail only to read the data from it? So I started to search for possibilities to debug the database lifecycle.

The system stores databases in the /data/data/package_name/databases folder by default.

In a command line using the adb (Android Debug Bridge - found in the android sdk tools library) you can access the databases on a running emulator like below:

  1. adb -s emulator-5554 shell
  2.  
  3. sqlite3 /data/data/package_name/databases/database_name

After this you can type normal SQL commands to test the content. For example:

  1. SELECT * FROM table_name;

This will list the table content (in an ugly format), or say that it does not exists.

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