疯狂Android讲义(1b)-基于监听&回调的事件处理-小结

基于监听的事件处理：

通过实现View类中内部接口来监听事件。“实现”是指通过View实例的setOnXXXListener()方法，将内部接口实例与View实例联系起来。View中内部接口如下：

Nested Classes class View.BaseSavedState Base class for derived classes that want to save and restore their own state in onSaveInstanceState(). class View.MeasureSpec A MeasureSpec encapsulates the layout requirements passed from parent to child. interface View.OnClickListener Interface definition for a callback to be invoked when a view is clicked. interface View.OnCreateContextMenuListener Interface definition for a callback to be invoked when the context menu for this view is being built. interface View.OnFocusChangeListener Interface definition for a callback to be invoked when the focus state of a view changed. interface View.OnKeyListener Interface definition for a callback to be invoked when a key event is dispatched to this view. interface View.OnLongClickListener Interface definition for a callback to be invoked when a view has been clicked and held. interface View.OnTouchListener Interface definition for a callback to be invoked when a touch event is dispatched to this view.

基于回调的事件处理：
View类继承了 KeyEvent.Callback等接口，获得了接口定义的抽象方法。事件发生时就可以回调码农实现的、事件对应的方法了。

 KeyEvent.Callback类型是public static interface

	Public Methods
	abstract boolean	onKeyDown(int keyCode, KeyEvent event) Called when a key down event has occurred.
	abstract boolean	onKeyLongPress(int keyCode, KeyEvent event) Called when a long press has occurred.
	abstract boolean	onKeyMultiple(int keyCode, int count, KeyEvent event) Called when multiple down/up pairs of the same key have occurred in a row.
	abstract boolean	onKeyUp(int keyCode, KeyEvent event) Called when a key up event has occurred.

1、以view为例，通过这种方式，Android为GUI组件提供了事件处理的回调方法。

2、由于Java是静态语言，所以无法为某个对象动态的添加方法，所以只能继承GUI组件类，并重写该类的事件处理方法。