Decompiling and displaying the source of an Android APK

This is a Windows-centric post, but it should be fairly straight-forward to make this work in Linux/MacOS by porting the script file and downloading the platform-correct version of JD-GUI.

Why do it

1. You are curious to see how an application does what it does by reading its code.
2.  You want to make sure that your application is properly obfuscated before making it public (i.e. you don't want people doing #1 and/or ProGuard is giving you grief).

You will need

• dex2jar: http://code.google.com/p/dex2jar/. This converts the bytecode from Dalvik's .dex format to the more standard .class format
• JD-GUI: http://java.decompiler.free.fr/?q=jdgui. This will decompile and display the code.
• A batch file to glue everything together (see below).

What to do

• Create a directory and name it something appropriate (for example apk-decompile).
• Download and extract dex2jar and JD-GUI in the directory you created.
• Make sure you rename the folders to match the file structure below:

• Create a new text file in the root directory (apk-decompile in our example) and name it "go.bat".
• Open it in notepad and paste the following:

echo off

REM Make sure we are working off the local directory.
set _=%~dp0
chdir /d "%_%"
echo Working directory is: "%_%"

IF "%~1"=="" GOTO BAD_SYNTAX

echo Converting dex to jar:
call dex2jar\dex2jar %1
echo.

echo Opening Class Viewer:
start "" jd-gui\jd-gui.exe %1.dex2jar.jar
echo.

echo DONT CLOSE THIS DIALOGUE UNTIL YOU'VE FINSHED CHECKING THE FILE AS IT WILL AUTOMATICALLY BE DELETED.
pause

del %1.dex2jar.jar

exit 0

:BAD_SYNTAX
echo Error! Incorrect syntax.
echo The correct syntax is:
echo  %0 ^<path_to_apk^>;
pause
exit 1

How to use this

• You can either use the command line and type the following: go.bat <path_to_apk>
• You can drag and drop an apk file onto go.bat.

Notes
 I'm certain that there are other, probably more efficient ways to do this but this suits my purposes (for now).

Two ListViews Side by Side in Android

The following XML shows how to place two ListViews side by side, add some seperator views and button bars for any actions needed.
Even though fragment now make the creation and maintenance this type of layout much easier, simple application might benefit from this without having to include the compatibility library.

The result will look like this:

(The layout file is after the break)

Getting a Bitmap out of a Zip file in Android (or Java in general)

The following function will extract an image from a zip file stored anywhere on the filesystem (for as long as the application has access to it).

It will return a bitmap object if the image is found or null otherwise. This function should work in pure java as well with minor alterations (replacing the Log calls with system.outs).

public Bitmap getBtimapFromZip(final String zipFilePath, final String imageFileInZip){
	Log.d(TAG, "Getting image '" + imageFileInZip + "' from '" + zipFilePath +"'");
	Bitmap result = null;
	try {
		FileInputStream fis = new FileInputStream(zipFilePath);
		ZipInputStream zis = new ZipInputStream(fis);
		ZipEntry ze = null;
		while ((ze = zis.getNextEntry()) != null) {
			if (ze.getName().equals(imageFileInZip)) {
				result = BitmapFactory.decodeStream(zis);
				break;
			}
		}
	} catch (FileNotFoundException e) {
		Log.e(Constants.TAG, "Extracting file: Error opening zip file - FileNotFoundException: ", e);
		e.printStackTrace();
	} catch (IOException e) {
		Log.e(Constants.TAG, "Extracting file: Error opening zip file - IOException: ", e);
		e.printStackTrace();
	}
	return result;
}

If you you use a wrapper function like this:

private void loadImage(ImageButton button, String image){
	// Use this drawable by default
	Drawable d = context.getResources().getDrawable(R.drawable.no_image);
	Bitmap b = getBtimapFromZip("path_to_zip_file", image);
	
	if(b != null){ // if the bitmap is not null, load that instead.
		d = new BitmapDrawable(b);
	}
	
	button.setImageDrawable(d);
}

you can have a fallback drawable to display if something goes wrong (the above bit is Android specific).

A few things to keep in mind:

1. To get the image out of the zip file you are scanning through all records in the archive sequentially. This could be a performance hit if you have many images. 
2. If the function returns null but you know that the image is in there, check that you havent accidentally archived the top directory along with the images when creating the zip.

Sending emails via Gmail (and others) in Java.

The following class will send emails from a java program. It definitely works on Gmail accounts and if you know the settings it should work on others as well. Keep in mind that it needs the javax.mail jar in your classpath.

You can use it like this:

private static void sendEmail(){  
     String[] toRecipients = {"he@it.com", "you@yes.you", "hey@there.com"};  
     String[] ccRecipients = {"this@concerns.you", "and@you.too"};  
     EmailSender es = new EmailSender("smtp.gmail.com", 465, "myEmail@gmail.com", "myPassword");  
     boolean res = es.sendEmail("myEmail@gmail.com", toRecipients, ccRecipients, "Hey guys!", "I can automate email sending now!");  
     if(res){  
          System.out.println("Woohoo!");  
     } else {  
          System.err.println("Hmmmm... Something went wrong...");  
     }  
}  

And here is the class:

Fixing the "Error getting final archive: Debug certificate expired on xx/xx/xxxx" problem

If you are developing Android applications for a while on the same computer (specifically for more than 365 days) you should be familiar with the "Error getting final archive: Debug certificate expired" error which will stop you from testing your applications.

When the Android SDK is installed, it creates a Debug Key which is used to automatically sign applications when you hit the run button and upload them to the Emulator/Test device. The certificate is only valid for 365 days after which you get the error above.

There are two ways to tackle this issue:

1. You can either get the Android SDK to recreate a debug key - and repeat this every 1 year.
2. You can create your own key and set the expiry date yourself.

Downloading and Parsing Vendor IDS files to CSV in VB.Net

The following function will parse an ids file and produce an equivalent CSV file. It has been tested with the following two ids files:

1. The PCI ven/dev list: http://pciids.sourceforge.net/v2.2/pci.ids
2. The USB ven/dev list: http://www.linux-usb.org/usb.ids

Ids files seem to have two sections; The first section contains the list of hardware and vendor IDs, while the second section has a list of known device classes, subclasses and programming interfaces. This function will only parse the first section. In principle, the only thing that one needs to do to add support for another ids, is to add a line telling the function when to stop parsing (see the idsToCsv() function below, at the beginning of the "Do While objReader.Peek()" loop).

It takes two parameters: "FileInPath" is the location of the OUI file and "FileOutPath" is the path of the CSVyou want to save to. If no file is there, one will be created automatically.

Checking if an Intent handler or Activity is present

Quite often in Android you need to call a 3rd party Intent or activity.
For example, to scan a barcode using the Barcode Scanner application, or to start the "hidden" Field Test application in HTC phones.

In order to make the life of a user easier, it is a good idea to check if the Intent Receiver/Activity exists before you attempt to invoke it. Some of the reasons being:

1. If a non-existent intent, you application will force close.
2. If the intent receiver is not present, you might want to redirect the user to the market to download the necessary application.
3. Depending on the existence of an intent you might want to make menu options appear/disappear.

This post contains two functions (isIntentAvailable() and isActivityAvailable())which can perform the checking and return a boolean accordingly.

Orange UK APN Settings

I've been flashing my phone quite often recently, and some ROMs do not contain the settings for the Orange UK APNs, so I am writing them here.

For the record, they are for Pay Monthly.

APN 1: Orange Internet

• Name: Orange Internet
• APN: orangeinternet
• Proxy: <Not set>
• Port: <Not set>
• Username: <Not set>
• Password: <Not set>
• Server: <Not set>
• MMSC: <Not set>
• MMS proxy: <Not set>
• MMS port: <Not set>
• MMS protocol: WAP 2.0
• MCC: 234
• MNC: 33
• Authentication Type: <Not set>
• APN type: default

APN 2: Orange MMS

• Name: Orange MMS
• APN: orangemms
• Proxy: <Not set>
• Port: <Not set>
• Username: <Not set>
• Password: <Not set>
• Server: <Not set>
• MMSC: http://mms.orange.co.uk
• MMS proxy: 192.168.224.010
• MMS port: 8080
• MMS protocol: WAP 2.0
• MCC: 234
• MNC: 33
• Authentication Type: <Not set>
• APN type: mms

Android Wifi password locations

The other day, I realised that I had forgotten my WiFi network password back at home.

The easy way to fix this would have been to use an already connected PC to access the router and change the password there, or to use an application like WirelessKeyView to recover the password of the said PC.

If I used method 1, I'd have to give the key to my housemates, which adds a bit of hassle.

When I tried method 2, the PC I was using was running XP I got a hex string which is not very user friendly (XP automatically converts WPA-PSK keys to a 64bit non-(easily?) reversible hash).

I then decided to try to get the key off my (rooted) Desire Z. Easy enough, the passwords are stored in plaintext in the following file:

/data/misc/wifi/wpa_supplicant.conf  

I then wrote a quick application to make the extraction a bit more painless (links at the bottom of the post), but when I was testing it on my Galaxy Tab, I realised that the file was not there. After a bit of digging around, I found the passwords here:

/data/wifi/bcm_supp.conf  

Also, here is the location of the file on the Streakroid ROM (this could be the default for all Dell Streaks, but as I don't have one I can't check):

/data/misc/wifi/wpa.conf  

The formatting of the files is identical and can be found here: http://linux.die.net/man/5/wpa_supplicant.conf, but the location is different (based on the whims of each developer/company I guess).

To access the files, you need root permissions.

Application Links:

• Market Link: https://market.android.com/details?id=aws.apps.wifiKeyRecovery
• Github Page: https://github.com/alt236/Wifi-Key-Recovery---Android
• Webpage: http://aschillings.co.uk/html/wifi_key_recovery.html

If anyone has a device on which the app does not work, do two things:

1. Make sure you are rooted.
2. If you are certain you are rooted and it still does not work, email me (my email can be found here: http://aschillings.co.uk/html/contact.html).

I have no way to contact you if you post anonymously in the comments section!

Ubuntu 10.10: Mimo UM-720S single screen setup

I recently needed to temporarily put a screen on a completely headless system (no graphics card installed), so I decided to use a MIMO UM-720s which was lying around (almost literally).

Naturally, was not as easy at it initially seemed...

First of all, this guide is heavily based on the one written by Andrew Simpson, which can be found here.

SECTION A: Getting it to work

Projector RS-232 Commands

This is a quick list of RS232 control commands for projectors.
The command list is by for not exclusive, but the most common ones should be listed.

If a projector model is not in the list, try any other codes from the same brand. They usually work.

Desire Z Modaco Rom r2 and protected Market applications.

After installing r2 of Paul's Desire Z ROM, I noticed that I could no longer find or download applications from the Market if they have their Protected flag set

To fix this, you need to use adb to pull the build.prop (a type of ini file for Android, containing information about the ROM) to your PC and change one line.

So in a command line, type the following:

 adb -d remount  
 adb -d pull /system/build.prop   

This will download the build.prop file from your phone to the current directory. Use a text editor (like notepad++) to open the file and change the following line:

 ro.build.fingerprint=htc_wwe/htc_vision/vision/vision:2.2.1/FRG83D/296256:userdebug/test-keys 

to this:

 ro.build.fingerprint=tmobile/htc_vision/vision/vision:2.2/FRF91/277427:user/release-keys

be careful not to change anything else.

Then push it back to the phone and reboot it, by typing:

 adb -d push build.prop /system/build.prop   
 adb -d reboot   

After this, you should be able to see protected applications in the market.

If you make a mistake while editing build.prop and something gets messed up, simply reflash the ROM.

R4i SDHC Card Problems and Solutions

I recently started having problems with my R4i SDHC cartridge, after changing the MicroSD card. The problems started when I swapped my old 2GB card to a SDHC one.

It would act slowly, corrupt save games and display "Savfile not founded! [sic]" message when some games are loaded.

To solve it, I did the following:

1. Copy all ROMs to the desktop.
2. Reformat the card using the Panasonic SD Formatter (http://panasonic.jp/support/global/cs/sd/download/index.html). I used version 2.0, with the default settings.
3. Replaced the spaces of the ROMs and .sav files with underscores ('_').
4. Copied everything back to the newly formatted card.
5. Updated the R4i's kernel (check their website). 

A couple of ROMs still failed to load (complaining about the Savfile), but once I moved to the root of the card, they were fine.


For the record, I use the R4i to mostly to write homebrew apps, and I do own the original cartridges of any ROMs I have loaded on it.

For the current (at the time of this writing) status flashcard legality, read here: http://www.bbc.co.uk/news/technology-10790835

Market upgrade to v2.2.11 and loss of application links

A couple of days ago my Desire Z silently updated the Market application to v2.2.11.

No idea what the update actually brings (I guess stability fixes) but it had the side effect of removing all application links in the "My Apps" section. That means that no application was listed as Installed, and the only apps in the screen were the purchased ones.

After trying to use the Market Doctor feature of Titanium Backup Pro (yes, I've paid for it) with little to no effect, I decided to delete the Market app's data.

And that was it. All applications were listed properly.

To delete the data, from the home screen go to
"Menu->Settings->Applications->Manage Applications->All->Market" and press the "Force Stop" button to stop the Market App from running, and the press the "Clear Data" button.

When you start the Market again, everything should be listed normally.

I can't guarantee that this will work for everyone or that it won't break anything else!