CODEWITHSUNDEEP
javaandroid
Nguyen Hoai Thanh
Nguyen Hoai Thanh

Reputation: 359

Which one "this"refer to?

If my class extends Activity and implements SensorEventListener, which one will this refer to - Activity or SensorEventListener? or Both? Thanks a lot.

 public class MainActivity extends Activity implements SensorEventListener

Upvotes: 0

Views: 69

Answers (3)

Seeker
Seeker

Reputation: 509

this keyword represents current activity or class or object.

e.g.

private int number;

public example(int number) {
    this.number = number;
}

here, this.number represents private int number variable and number is methods int number.

Another example would be (its the same as in java)

class example implements ActionListener{
public static void main(String[] args)
{
  JButton button = new JButton();
  button.addActionListener(this);
}

}

Since you have implemented the action listener to your class / project when you type this, it will call the action listener library.

Upvotes: 1

SDJMcHattie
SDJMcHattie

Reputation: 1699

this refers to the current instance of the class. implements is for an interface so this can never refer to that. You cannot create an instance of an interface, only of classes. Activity is the superclass of MainActivity and is also not having an instance of it made. The instance will be of MainActivity

However, although this is a bit pointless, you can cast this to all of MainActivity, Activity or SensorEventListener without any problems.

Upvotes: 2

DonCallisto
DonCallisto

Reputation: 29912

this will refer to MainActivity that will be the instance of the class

Of course if you "change the contest" and look to an instance of Activity: in that case this could refer to Activity but looking to your question, the answer is definitely MainActivity

Upvotes: 2

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