Android : How I declare Textview variable

My question is how I declare Textview variable in javacode?

My code is here:

TextView tv1 = new TextView(MainActivity.this);

i want using tv1 in this function:

build.setPositiveButton("Tamam", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {

}

I try this code : tv1 = new TextView(MainActivity.this) but i had this issue:

Multiple markers at this line - Syntax error on token "new", delete this token - TextView cannot be resolved to a variable - The final local variable tv1 cannot be assigned, since it is defined in an enclosing type