What different between class_name.this and this

Question

I see some code use class_name.this as a parameter for its context, and sometimes use this directly in another demo code. May I assume that this is a abbreviation of class_name.this?

Answer 1

We use this when if the class references can be type-casted to Context. And when this object cann't be, then we use ClassName.this (BUT only if the class is child/ super child [subclass] of Context class. like Activity/ Services)

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Read What is 'Context' on Android?

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Let me explain by example code (For example I am using Activity and AsyncTask)

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        this.startActivity(intent); 
        // or 
        MainActivity.this.startActivity(intent); 
        // Both are same here. 
    }

    private class TestTask extends AsyncTask<Void, Void, Void> {

        @Override
        protected Void doInBackground(Void... params) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            this.startActivity(intent); // You can not do. Because "this" is the current object of AsyncTask not of Activity. 
            // So you can only use
            MainActivity.this.startActivity(intent); 
        }
    }
}

Answer 2

1.In Outer Class you directly use "this" reference
2.In Inner Class Or Abstract Class implementation Or Interface implementation use "classname.this" reference

Answer 3

This is special syntax which allows to access outer class instance from an inner class. Consider this

class X {
    class Y {
        void y() {
            Object y = this;
            Object x = X.this;
        }
    }
}

Answer 4

ClassName.this allows you to refer to the external class even when inside a nested class.

For example MyClickListener is nested inside MainAcvitiy:

private class MyClickListener implements OnClickListener
{
    @Override
    public void onClick(View v) 
    {
       Toast.makeText(MainActivity.this, "I have been clicked", Toast.LENGTH_SHORT).show();
    }
}

You need the reference to MainActivity.this because the current value of this is MyClickListener and you don't want to bother passing in a reference to the Activity here

Answer 5

this is used to refer the current or live instance of class , but in cases where u have to use nested classes and nested class wants to access the member of outer class then its done by using class_name.this as it will make clear which class u are referring to.

refer this questions :-
What is the difference between Class.this and this in Java