如何让alertdialog选择完后自动关闭

builder.setIcon(R.drawable.ic_system)
                    .setTitle("串口号")
                    .setSingleChoiceItems(mPorts, mSelectIndex,
                            new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog,
                                        int whichButton) {
                                    mSelectIndex = whichButton;
                                    tv_mainCtlPort
                                            .setText(mPorts[mSelectIndex]);
                                    syscfg.setMainCtlPort(mSelectIndex);
                                    intent.putExtra(Constant.SYSSETING_STRING,
                                            syscfg);
                                    SysSettingActivity.this.setResult(
                                            Constant.SAVESYSCONFIG, intent);
                                    dialog.dismiss();
                                }
                            })
                    .setNegativeButton("取消",
                            new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog,
                                        int whichButton) {

                                }
                            });

　　用 DialogInterface.OnClickListener点击事件传的dialog就可以啊，dialog.dismiss();