What does “this” mean? [duplicate]

Answer 1

The this keyword is a reference to the current object. It is used to pass this instance of the object, and more.

For example, these two allocations are equal:

class Test{

    int a;

    public Test(){
        a = 5;
        this.a = 5;
    }

}

Sometimes you have a hidden field you want to access:

class Test{

    int a;

    public Test(int a){
        this.a = a;
    }

}

Here you assigned the field a with the value in the parameter a.

The this keyword works the same way with methods. Again, these two are the same:

this.findViewById(R.id.myid);
findViewById(R.id.myid);

Finally, say you have a class MyObject that has a method which takes a MyObject parameter:

class MyObject{

    public static void myMethod(MyObject object){
        //Do something
    }

    public MyObject(){
        myMethod(this);
    }

}

In this last example you passed a reference of the current object to a static method.

Also why is it in this example that a button is not defined with Button but with View, what is the difference?

In Android SDK, a Button is a subclass of View. You can request the Button as a View and cast the View to a Button:

Button newButton = (Button) this.findViewById(R.id.new_button);

Answer 2

this refers to the current instance of a class

Answer 3

this in Java is a reference to the current object instance. So if you are writing a method for class MyClass, this is the current instance of MyClass.

Note that in your case, writing this.findViewById(...) isn't really necessary, and may be considered bad style.

Answer 4

"this" in object oriented languages such as java, c# is a reference to the object on which you are invoking the method or whose data you are accessing.

See if this link is helpful for you in understanding the "this" more -

http://docs.oracle.com/javase/tutorial/java/javaOO/thiskey.html

Answer 5

this is referring to the instance of the object that is being acted upon.

In the case that you have above, this.findViewById(R.id.continue_button) this is referring to a method in a parent class (Specifically either Activity.findViewById() or View.findViewByid(), assuming you are writing your own subclass of Activity or View!).

Answer 6

"this" is the current object instance.

class Blaa
{
   int bar=0;
   public Blaa()
   {}
   public void mogrify(int bar,Blaa that)
   {
       bar=1; //changes the local variable bar
       this.bar=1; //changes the member variable bar. 
       that.bar=1; //changes "that"'s member variable bar. 
   }

}