title: android: xml attribute android:onClick, why the method needs View parameter
body: <p>When I create an android:onClick attribute in the activity's xml, the method defined by onClick needs to have the View parameter, why View?</p>
  
  <p>i.e.
  onClick method in my activity----------> public void sayHello(View v){...}</p>
  
  <p>consider the next code, I'm not using the view variable, but I still need to pass it in method, how come?:</p>
  
  <pre><code>public void onClick(View view){
          TextView t= new TextView(this);
          t=(TextView)this.findViewById(R.id.textView2);
          t.setText("new text");
      }
  </code></pre>