Fragment的构造函数

   

    默认的构造函数，每个Fragment必须有一个空的构造函数，这可以让它在Activity中恢复时实例化。强烈建议Fragment的子类不要拥有其他有参数的构造函数，因为这些构造器不会在Fragment重新实例化时被调用；取而代之， 调用者能以setArguments(Bundle)提供arguments，然后被Fragment以getArguments()取回。

    应用程序一般不要实现构造器。一个可以使用的Fragment的开始代码是onAttach(Activity)，事实上这是Fragment和Activity交接的地方。有些应用程序也会去实现onInflate(Activity, AttributeSet, Bundle)方法从layout资源中获得属性，但是在这里应该特别小心，因为这发生在Fragment附加上它的Activity时候。

 

来自官方API：

Default constructor. Every fragment must have an empty constructor, so it can be instantiated when restoring its activity's state. It is strongly recommended that subclasses do not have other constructors with parameters, since these constructors will not be called when the fragment is re-instantiated; instead, arguments can be supplied by the caller with setArguments(Bundle) and later retrieved by the Fragment with getArguments().

Applications should generally not implement a constructor. The first place application code an run where the fragment is ready to be used is inonAttach(Activity), the point where the fragment is actually associated with its activity. Some applications may also want to implementonInflate(Activity, AttributeSet, Bundle) to retrieve attributes from a layout resource, though should take care here because this happens for the fragment is attached to its activity.