AlertDialog不支持onBackPressed

AlertDialog alertDialog = new AlertDialog.Builder(context)
    .setTitle("提示")
    .setMessage("确定要关闭对话框吗？")
    .setPositiveButton("确定", null)
    .setNegativeButton("取消", null)
    .create();

alertDialog.setOnKeyListener(new DialogInterface.OnKeyListener() {
    @Override
    public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_UP) {
            alertDialog.dismiss();
            return true;
        }
        return false;
    }
});

alertDialog.show();

@Override
public void onBackPressed() {
    if (alertDialog != null && alertDialog.isShowing()) {
        alertDialog.dismiss();
    } else {
        super.onBackPressed();
    }
}