AlertDialog

 
​x
AlertDialog.Builder dialog = new AlertDialog.Builder(MainActivity.this);
​
dialog.setTitle("This is a dialog");
dialog.setMessage("Something important");
dialog.setCancelable(false);
dialog.setPositiveButton("OK", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialogInterface, int i) {
​
    }
});
dialog.setNegativeButton("NO", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialogInterface, int i) {
​
    }
});
dialog.show();