Listener是一个接口
An
event listener is an interface in the View class that contains a single callback
method. These methods will be called by the Android framework when the View to
which the listener has been registered is triggered by user interaction with the
item in the UI.
1.View里面有接口的声明，以及接口的定义（接口里面有方法）。
2.为View设置监听器（特定已经实现的接口）。
public
class View implements Drawable.Callback, KeyEvent.Callback,
AccessibilityEventSource {
private OnKeyListener mOnKeyListener;
public interface OnKeyListener
{
/**
* Called when a key is
dispatched to a view. This allows listeners
to
* get a chance to respond
before the target view.
*
* @param v The view the
key has been dispatched to.
* @param keyCode The code for the physical key that was
pressed
* @param event The
KeyEvent object containing full information
about
* the
event.
* @return True if the
listener has consumed the event, false
otherwise.
*/
boolean onKey(View v, int
keyCode, KeyEvent event);
}
public void setOnKeyListener(OnKeyListener l)
{
mOnKeyListener =
l;
}