Android Bridge

Wi-Fi Keep Alive / On for Kindle Fire

2012-02-07T08:41:00.000-08:00

I have uploaded my first app to Amazon App Store, Check it out here

Wi-Fi Keep Alive

It is a simple for kindle fire to keep the wi-fi connection always on even the device screen goes off. This might use some extra battery power to keep the Wi Fi up but it wont disconnect your streaming music :)

debug.keystore keystore password ?

2012-01-31T00:26:00.000-08:00

Today when i wanted to play with Google Maps, i had to generate a new Certificate fingerprint to include Maps. To generate a new Certificate fingerprint you need to use the keytool that comes with the SDK,

so i executed this line in the CMD,

keytool -list -keystore .android/debug.keystore

but it's asking for a password, duh! after few seacrches on google, I found out, it's android, type android and you shall passed

How to add icons to Preference example in Android

2011-12-29T02:20:00.000-08:00

If you are having a pain in the ass getting this to work. Download the example from here

http://www.ziddu.com/download/17996784/preference_icon_example.zip.html

StackOverflow error in Eclipse ?

2011-12-07T22:57:00.000-08:00

Today, friend of mine Kitaro Nu shared this information with me.

This error is likely to happen if you have two library projects and they both refer each other.

· Project A import project B and Project B import Project A .

Unable to create editor ID org.eclipse.jdt.ui.PropertiesFileEditor: Editor could not be initialized. Java heap space

2011-12-01T02:47:00.000-08:00

Today, after I took the latest version of a component and try to rebuild the work space i started to getting this error.

To solve this,

1. Had to close eclipse and restart

2. Run eclipse with clean command

\eclipse\eclipse.exe -clean

3. delete

workspace\.metadata\.plugins\org.eclipse.jdt.core

workspace\metadata\.plugins\org.eclipse.core.resources\.history

worked for me!

How to encrypt a serializable class in Android

2011-11-28T21:00:00.000-08:00

public boolean save(YourClass pref){

boolean isSuccess = false;

try {

final File persistedFile = new File("/sdcard/sr.dat");

if(persistedFile.exists())

persistedFile.delete();

OutputStream file = new FileOutputStream(persistedFile);

BufferedOutputStream buffer = new BufferedOutputStream(file);

Cipher desCipher = getCipher(Cipher.ENCRYPT_MODE);

CipherOutputStream cos = new CipherOutputStream(buffer, desCipher);

ObjectOutputStream oos = new ObjectOutputStream(cos);

oos.writeObject(pref);

oos.flush();

oos.close();

} catch (IOException ex) {

Log.d(TAG, ex.getMessage());

isSuccess = false;

} catch (InvalidKeyException e) {

Log.d(TAG, e.getMessage());

isSuccess = false;

} catch (InvalidKeySpecException e) {

Log.d(TAG, e.getMessage());

isSuccess = false;

} catch (NoSuchAlgorithmException e) {

Log.d(TAG, e.getMessage());

isSuccess = false;

} catch (NoSuchPaddingException e) {

Log.d(TAG, e.getMessage());

isSuccess = false;

}

return isSuccess;

}

private Cipher getCipher(int opmode) throws InvalidKeyException, InvalidKeySpecException, NoSuchAlgorithmException, NoSuchPaddingException {

byte key[] = "Aruna Tennakoon".getBytes();

DESKeySpec desKeySpec = new DESKeySpec(key);

SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");

SecretKey secretKey = keyFactory.generateSecret(desKeySpec);

// Create Cipher

Cipher desCipher = Cipher.getInstance("DES/ECB/PKCS5Padding");

desCipher.init(opmode, secretKey);

return desCipher;

}

public Preference load(){

Preference repo = null;

try {

final File persistedFile = File("/sdcard/sr.dat");

if(!persistedFile.exists()) {

// sr is not created yet. Create one and return

return;

}

Cipher desCipher = getCipher(Cipher.DECRYPT_MODE);

FileInputStream fis = new FileInputStream(persistedFile.getAbsolutePath());

BufferedInputStream bis = new BufferedInputStream(fis);

CipherInputStream cis = new CipherInputStream(bis, desCipher);

ObjectInputStream ois = new ObjectInputStream(cis);

repo = (YourClass) ois.readObject();

ois.close();

} catch (FileNotFoundException e) {

Log.d(TAG, e.getMessage());

} catch (StreamCorruptedException e) {

Log.d(TAG, e.getMessage());

} catch (IOException e) {

Log.d(TAG, e.getMessage());

} catch (InvalidKeyException e) {

Log.d(TAG, e.getMessage());

} catch (InvalidKeySpecException e) {

Log.d(TAG, e.getMessage());

} catch (NoSuchAlgorithmException e) {

Log.d(TAG, e.getMessage());

} catch (NoSuchPaddingException e) {

Log.d(TAG, e.getMessage());

} catch (ClassNotFoundException e) {

Log.d(TAG, e.printStackTrace());

}

return repo;

}

how to get the ip address of android phone?

2011-11-23T19:24:00.000-08:00

private String getLocalIpAddress() {

try {

for (Enumeration en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {

NetworkInterface intf = en.nextElement();

for (Enumeration enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {

InetAddress inetAddress = enumIpAddr.nextElement();

if (!inetAddress.isLoopbackAddress()) { return inetAddress.getHostAddress().toString(); }

}

} catch (SocketException ex) {

Log.e("ServerActivity", ex.toString());

}

return null;

}

'Conversion to Dalvik format failed with error 1' and 'java.lang.IllegalArgumentException: already added: '

2011-11-16T19:30:00.000-08:00

Recently we moved to Android SDK tools Rev 15 , In my opinion it has may problems comparing to previous versions of the SDK and should stick with the previous version if you are developing a huge applications and have library projects referenced.

Today, I got this error and few hours of Googling found the solution,

Remove the source folder link in Project properties->Java Build Path->Source

Clean and add the projects back, You will see that it will add the projects as jar files under "Library Projects" not as project_src anymore.

How to do a simple visible animation in Android

2011-11-07T19:05:00.001-08:00

public void showConfigurationBar() {

AnimationSet set = new AnimationSet(true);

Animation animation = new AlphaAnimation(0.0f, 1.0f);

animation.setDuration(500);

set.addAnimation(animation);

animation = new TranslateAnimation(Animation.RELATIVE_TO_SELF, 0.0f,

Animation.RELATIVE_TO_SELF, 0.0f, Animation.RELATIVE_TO_SELF,

1.0f, Animation.RELATIVE_TO_SELF, 0.0f);

animation.setDuration(500);

set.addAnimation(animation);

RelativeLayout configBar = findViewById(R.id.baridhere);

configBar.setVisibility(View.VISIBLE);

configBar.startAnimation(set);

}

How to generate a MD5 Hash in Android

2011-11-07T19:00:00.000-08:00

public static String getMd5Hash(String input) {
try {
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] messageDigest = md.digest(input.getBytes());
BigInteger number = new BigInteger(1, messageDigest);
String md5 = number.toString(16);

while (md5.length() < 32)
md5 = "0" + md5;

return md5;
} catch (NoSuchAlgorithmException e) {
Log.e("MD5", e.getLocalizedMessage());
return null;
}
}

Eclipse Layout Editor Graphical Layout is not Showing or missing ?

2011-11-01T02:56:00.001-07:00

Specify the Android Layout Editor as the default for Android XML files under Preferences -> General- >Editors->File Associations.

1. If Android layout editor is missing Add Android Layout Editor and make it default.

2. Close eclipse and restart. Otherwise this will not work.

CountDownTimer Error: Can't create handler inside thread that has not called Looper.prepare()

2011-10-31T04:43:00.000-07:00

Today I was getting this error "Can't create handler inside thread that has not called Looper.prepare()" in a CountDownTimer. All this time this code used to work perfectly but suddenly it stopped.

Problem is, in CountDownTimer.java (Android source code) it creates a mHandler inside the code which makes the caller should call the CountDownTimer class on UI thread which is not possible in my case. So I created a separate Timer class,

Timer cTimer = new Timer();

private final static int START_FROM = 60;

cTimer.scheduleAtFixedRate(new TimerTask() {

int i = START_FROM ;

public void run() {

Log.d(TAG, "Comparison will start in:" + i--);

if (i< 0) {

cTimer.cancel();

// Do something

}

}, 0, 1000);

How to enable/disable Mobile Data on Android 2.3

2011-10-25T03:32:00.000-07:00

Today, colleague asked me whether i know how to enable and disable mobile internet on Android ? Actually, I was curious about this for sometime and never had the time to look into how to do this. So this is how to do it.

I tired it on Android 2.3 i tried this code and it worked! When I looked into Android source code I saw this method is available 2.2 R1 up.

private boolean getMobileDataEnabled() {

try {

Method method = connectivityManager.getClass().getMethod("getMobileDataEnabled");

return (Boolean) method.invoke(connectivityManager);

} catch (Exception e) {

e.printStackTrace();

return false;

}

private void setMobileDataEnabled(boolean on) {

try {

Method method = connectivityManager.getClass().getMethod("setMobileDataEnabled", boolean.class);

method.invoke(connectivityManager, on);

} catch (NoSuchMethodException e) {

e.printStackTrace();

} catch (Exception e) {

e.printStackTrace();

}

If you are using 2.2 R1 or later try this code.

android.content.OperationApplicationException: wrong number of rows: 0

2011-10-19T04:25:00.000-07:00

Today I got this error tying to update a contact in Android 2.3 Nexus S device which was working fine on Motorola Milestone (Android 2.1 - update 1). Reason was I was getting the "withExpectedCount" parameter as 1

ops.add(ContentProviderOperation. newInsert(addCallerIsSyncAdapterParameter(ContactsContract.Data.CONTENT_URI))

.withValue(ContactsContract.Data.RAW_CONTACT_ID, contact.getId())

.withValue(ContactsContract.Data.MIMETYPE, CommonDataKinds.Phone.CONTENT_ITEM_TYPE)

.withValue(CommonDataKinds.Phone.NUMBER, phone)

.withValue(CommonDataKinds.Phone.TYPE, cm.getType()).withExpectedCount(1).build());

When i removed it it worked fine .. Looks like if the original and updating content values are same it does not update the row :|

How to brick your android device?

2011-09-27T01:11:00.000-07:00

Today, While I was digging into android source code, I found this. Never tried it. Drop me a message here if you do.

package com.android.server;

import android.content.Context;
import android.content.Intent;
import android.content.BroadcastReceiver;
import android.os.SystemService;
import android.util.Log;

public class BrickReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
Log.w("BrickReceiver", "!!! BRICKING DEVICE !!!");
SystemService.start("brick");
}
}

http://www.netmite.com/android/mydroid/frameworks/base/services/java/com/android/server/BrickReceiver.java

How to debug Android source code in Eclipse?

2011-09-23T03:12:00.000-07:00

Today, I wanted to know what's going on inside Android because it was keep throwing an exception . So i wanted to check how to debug an Android application right from Eclipse IDE. When I googled I found this link,

http://android.opensourceror.org/2010/01/18/android-source/

but it says how to debug a single version of android eg. Cupcake. Now problem is how to debug multiple versions of Android ?

it's easy.

all you have to do is open the .project in notepad
\workspace\.metadata\.plugins\org.eclipse.jdt.core\.org.eclipse.jdt.core.external.folders

and another element to the section.



         .link0
         2
         C:/Aruna/Android/android-sdk_r08-windows/android-sdk-windows/Cupcake
  
     
         .link1
         2
         C:/Aruna/Android/android-sdk_r08-windows/android-sdk-windows/Donut

IllegalStateException: Couldn't init cursor window

2011-09-23T03:10:00.000-07:00

Today one of our application started getting this exception.

java.lang.IllegalStateException: Couldn't init cursor window at android.database.CursorWindow.native_init(Native Method) at android.database.CursorWindow.(CursorWindow.java:41) at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:277) at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:269)

After few hours of googling, I found the solution to this problem. Solution is to close the Cursor after after you are done!This exception is thrown here

if (!window->initBuffer(localOnly)) { jniThrowException(env, "java/lang/IllegalStateException", "Couldn't init cursor window"); delete window; return; }

localOnly is defined in

CursorWindow.h

#define MAX_WINDOW_SIZE (1024 * 1024)

So, There are two possible causes to throw this exception. 1. Your mobile phone is out of memory.2. You are fetching something out of the database more than 1M. If there is a logical way to divide your queries into discrete chunks, you could do incremental queries and use CursorJoiner to stitch them together that might help you if you are dealing with big chuck of data.

So lesson learned, Close the cursor in a try finally block

Cursor cursor;

try {

cursor.open();

}

finally{

if(cursor.isOpen()) {

cursor.close();

}

Error retrieving parent for item: No resource found that matches the given name 'android:WindowTitleBackground'.

2011-09-07T08:04:00.000-07:00

Today while trying to compile a project I got for github I got this error.

Error retrieving parent for item: No resource found that matches the given name 'android:WindowTitleBackground'.

It's so annoying because it worked perfectly in one machine and on my laptop it did not. When I was almost given up I thought of replacing the platform tools with old platform tools and it worked!!

Download the revision 11 tools from here

http://dl.google.com/android/repository/tools_r11-windows.zip

and rename your platform-tools folder in android-sdk-windows and paste this there. That should work!

How call a method/function inside a APK file in Android?

2011-08-22T06:45:00.000-07:00

Today I came across this piece of code and thought of sharing it with others.

PathClassLoader c = new PathClassLoader("/system/app/Mms.apk", getClassLoader());
Class.forName("com.android.mms.util.ContactInfoCache", true, c)
.getMethod("init", Context.class).invoke(null, context);
Class.forName("com.android.mms.transaction.MessagingNotification", true, c)
.getMethod("updateAllNotifications", Context.class).invoke(null, context);

This piece of code will trigger Android new message arrival notification. Interesting ...

Type The method compareTo(Request) of type Request must override a superclass method ? haa?

2011-08-04T22:39:00.000-07:00

We were working on Eclipse Galileo and moved to the new version Indigo but some of the projects that were working fine in Galileo started trowing this exception. Problem is in Galileo Java compiler compliance is set to JRE 1.6 but in Indigo it's set to 1.5 for some reason.

So to fix this error you need to change the compliance to 1.6 back, To do this, Go to your Window -> Preferences -> Java -> Compiler -> Set to 1.6 and set the java compiler level to 1.6 and also make sure you select JRE 1.6 to execute your program from eclipse.

Android ContentObserver not getting notify ?

2011-08-01T04:18:00.000-07:00

Today, I ran into a problem where my content observer is not getting notify when I delete something. After hours of searching I realized, sometime you need to set the
notifyForDescendents parameter as true. Weird but it worked!

Eg.

registerContentObserver(uri, true, observer);

How to use ACTION_TIME_TICK broadcast ?

2011-08-01T03:48:00.000-07:00

Today, I was looking into how to track change notification to the camera folder in Android. While Googling for this, I came across ACTION_TIME_TICK broadcast event.

Android Doc says
public static final String ACTION_TIME_TICK
The current time has changed. Sent every minute. You can not receive this through components declared in manifests, only by exlicitly registering for it with Context.registerReceiver().

Sometimes we use a backgroud timer in our application to check for something in a continues loop but I think listening to this event is much better approach, but you have to make sure it's thread safe.

How to use.

@Override
public void onCreate(){
super.onCreate();

registerReceiver(
new ThikReceiver(),
new IntentFilter(Intent.ACTION_TIME_TICK));
}
}

public class ThikReceiver extends BroadcastReceiver {

@Override
public void onReceive(Context context, Intent intent) {
if(intent.getAction().compareTo(Intent.ACTION_TIME_TICK) == 0)
// Do something
else
// Do something else
}
}

How to create a thread in android without hurting the UI

2011-07-29T02:30:00.000-07:00

Sometimes when we want to do something out of the ordinary like pushing something to the server while user is playing a game or checking emails we create Threads. If you do not set the thread priority to low this might hurt the UI performance.

Correct way to do is to call setPriority in the thread class.

SomeTaskThread someTaskThread = new SomeTaskThread();
someTaskThread.setPriority(Thread.NORM_PRIORITY-1); //Make the background thread low priority. This way it will not affect the UI performance
someTaskThread.start();

or you can use AsyncTask class.

Unable to find instrumentation target package ? duh!

2011-07-18T04:23:00.001-07:00

Today I was trying to write some test cases after i got inspired by this link

Problem was I was keep getting "Unable to find instrumentation target package" Error and not sure how to fix it. Well there are few ways to fix this problem. Easy way out is:

1.Double click on the AndroidManifest.xml

Delete any "instrumentation" tags

2.Goto Instrumentation Tab
3.Click Add
4.Select Instrumentation
5. Select the name and target package.

This should work. Trying to add the Instrumentation manually is a nightmare.

Hope this will help to someone else

How do I investigate an Application Not Responding (ANR) in Android?

2011-07-03T23:32:00.000-07:00

Today I got an ANR error and it's really annoying because you know you have done something wrong and not sure where to look for to find out the problem.

When I googled, I found this on StackOverFlow.

"An ANR happens when some long operation takes place in the "main" thread. This is the event loop thread, and if it is busy, Android cannot process any further GUI events in the application, and thus throws up an ANR dialog." - From Stackoverflow

so, how to diagnose the problem, it's easy,

adb shell cat /data/anr/traces.txt

will drump all the appplication not responding traces to the command prompt. (Make sure to change the command prompt buffer size otherwise you can not see the full log out)