Android :: Why Are OnCreate() OnStart() Etc Called When Handset Orientation Is Changed

I got my hands on Android which is really fun. But at some point I don't seem to understand the concept. I've got a Main class which reads like this:

CODE:....

In the onCreate(...) I set the layout to setContentView(R.layout.main); and add an OnTouchEvent Listener to the sole View in main.xml: myView.setOnTouchListener(new OnTouchListener() {@Override public boolean onTouch(View v, MotionEvent event){...

As you can see I also implemented a SensorEventListener which is used if required. All works fine so far.

But my problem is this (at this point my misunderstanding kicks in): whenever I rotate the device the onCreate(), onStart() etc. methods are called, causing my app to act as if it just started. Furthermore, I feel unable to implement an onSizeChanged(int w, int h, int oldw, int oldh) { ... } Listener.

Can anyone please explain where my error in reasoning is? I am working on a tiny app which is more or less done, except for the just mentioned bug(s). Maybe I got it all wrong but it does what it is supposed to do (i.e. sending touch positions and accelerometer data over the network via UDP).