Android重写回来键处理事件

@Overridepublic void onBackPressed() {Dialog dialog = new AlertDialog.Builder(this).setTitle("信息提示").setMessage("确定要退出系统吗?").setPositiveButton("确定", new DialogInterface.OnClickListener() {    @Override    public void onClick(DialogInterface dialog, int which) {        finish();    }}).setNeutralButton("取消", new DialogInterface.OnClickListener() {    @Override    public void onClick(DialogInterface dialog, int which) {        return;    }}).create();dialog.show();}