C Array and pointer

int _tmain(int argc, _TCHAR* argv[])
{
int a[2][3] = { 0 };

printf("address of a = %p %p %p %p\n", a, &a, &a[0], &a[0][0]); // all equal a
printf("address of a + 1 = %p %p %p %p\n", a+1, &a+1, &a[0]+1, &a[0][0]+1); // a+3*4 ( 4 bytes per int), a+6*4, a+3*4,a+4

}

passing data from intent

http://stackoverflow.com/questions/768969/passing-a-bundle-on-startactivity

1) Use the Bundle from the Intent:

Intent mIntent = new Intent(this, Example.class);
Bundle extras = mIntent.getExtras();
extras.putString(key, value);  

2) Create a new Bundle

Intent mIntent = new Intent(this, Example.class);
Bundle mBundle = new Bundle();
mBundle.putString(key, value);
mIntent.putExtras(mBundle);

3) Use the putExtra() shortcut method of the Intent

Intent mIntent = new Intent(this, Example.class);
mIntent.putExtra(key, value);

implements Serializable

you can stream your Java object to a sequence of byte and restore these objects from this stream of bytes. 

http://www.vogella.com/tutorials/JavaSerialization/article.html

“implements Runnable” vs. “extends Thread”

http://stackoverflow.com/questions/541487/implements-runnable-vs-extends-thread

by extending Thread, each of your threads has a unique object associated with it, whereas implementing Runnable, many threads can share the same object instance.

Output of the above program.

ImplementsRunnable : Counter : 1
ImplementsRunnable : Counter : 2
ImplementsRunnable : Counter : 3
ExtendsThread : Counter : 1
ExtendsThread : Counter : 1
ExtendsThread : Counter : 1

Looper and thread

When I created a handler inside a thread ( not main thread ), the program will terminate directly.

According the logcat log, it needs Looper, after added the Looper inside the thread, it works.

Building a Notification with a pendingintent

http://developer.android.com/training/notify-user/build-notification.html

Remember to create your own notification icon in the drawable folder, otherwise you can't figure out whether the notification is showing up or not.

Content provider is not thread safe.

http://www.androiddesignpatterns.com/2012/10/sqlite-contentprovider-thread-safety.html