Model–view–controller (MVC) is a software design pattern
commonly used for developing user interfaces that 
divide the related program logic into three interconnected elements. 

• 111,211,311 level -- one textbased app, no need MVC
• GUI programming must follow at least View-Controller
• Small projects usually have no Model
• Android MVCR -- Model, View, Controller + Resources

• Model => Data - Java classes, files
• View => UI - layout+resources (sometimes combined with Java as control)
• Controller => Code - Java MainActivity classes (can combine)

• Manifest
• Activities -- Controller
• Layout -- View
• Resource
  • anim/
  • color/
  • drawable/
  • layout/
  • menu/
  • values/
    • colors.xml
    • dimens.xml
    • strings.xml
    • styles.xml
    • themes
  ...

• (Create model if necessary)
• Use layout+resources to define UI
• Bind UI widgets and provide event handler in Contrller -- binding then callback

Button btn = (Button) findViewById(R.id.button);

IDE Tip: Use TAB key to auto-complete
IDE Tip: Alt+Enter to auto import

Text #1 pp72-73	
protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.activity_main);
}

public void addNumber(View v) {
	TextView tv = ((TextView) findViewById(R.id.textHello));
	int currVal = Integer.parseInt(tv.getText().toString());
	tv.setText((++currVal) + "");
}

public class MyOnClickListener implements View.OnClickListener { 
	public void onClick(View v){
		//process event
	}
}
protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.activity_main);

	Button  button = (Button)findViewById(R.id.button);
	MyOnClickListener Listener = new MyOnClickListener();
	button.setOnClickListener(Listener);
}

protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.activity_main);

	Button  button = (Button)findViewById(R.id.button);
	button.setOnClickListener(
		new View.OnClickListener() {
			@Override
			public void onClick(View view) {
				//Implement event handling
				Context ctx =  MainActivity.this;
				Toast.makeText(ctx, "Hello", Toast.LENGTH_LONG).show();
			}
		});
}

Tip: Tools -> Clean Project

public class MainActivity extends Activity implements View.OnClickListener {
protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.activity_main);

	Button  button = (Button)findViewById(R.id.button);
	button.setOnClickListener(this);
}
@Override
public void onClick(View view) {
	//Handle Event
	Context ctx =  MainActivity.this;
	Toast.makeText(ctx, "Hello Callback #4", Toast.LENGTH_LONG).show();
}