ContextWrapper.getApplicationContext():Return the context of the single, global Application object of the current process
生命周期是整个应用，应用摧毁它才摧毁
View.getContext():Returns the context the view is running in
this(activity or service):返回当前activity or service的上下文，属于activity or service，activity or service 摧毁他就摧毁
ContextWrapper.getBaseContext():Return the base context as set by the constructor or setBaseContext
返回由构造函数指定或setBaseContext()设置的上下文
Activity.getParent():Return the parent activity if this view is an embedded child.
Activity.getApplication():Return the application that owns this activity