。。。 Event Registration method of two ...

In Mainactivity.java, add the following code in the OnCreate () method:

It is important to remember that the definition of a variable is defined outside the anonymous class, which is placed in the OnCreate () method, because the anonymous class is equivalent to a property in another class that cannot access the mainactivity inside. If you define a control variable in the OnCreate () method, you must add the final keyword (this method is deprecated)

Or you can define a control variable directly in the class so that you do not need to add the final keyword:

This is OK!!!

。。。 Event Registration method of two ...