show alert dialog from anywhere

alert.java

 new AlertDialog.Builder(getActivity())
        .setTitle(getString(R.string.dialog_title))
        .setMessage(getString(R.string.dialog_text))
        .setPositiveButton(getString(R.string.ok), new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                // OK clicked

                }
            })
            .setNegativeButton(getString(R.string.cancel), new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                // CANCEL clicked

                }
            }).show();