Android service里面启动alertdialog

public void showSystemDialog(String showInfo, final int flag)  
    {  
        AlertDialog.Builder b = new AlertDialog.Builder(context);  
        b.setMessage(showInfo);  
        b.setPositiveButton("确定", new DialogInterface.OnClickListener()  
        {  
            public void onClick(DialogInterface dialog, int id)  
            {  
  
                switch (flag)  
                {  
                    case 0:  
                        Intent intent = new Intent(  
                                Settings.ACTION_WIRELESS_SETTINGS);  
                        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);  
                        context.startActivity(intent);  
                        break;  
                    case 1:  
  
                    case 3: // 如果是GPRS,则提醒   
                        if (moblieFlag == false)  
                        {  
                            moblieFlag = true;  
                        }  
                    default:  
                        break;  
                }  
                d.dismiss();  
            }  
        }).setNegativeButton("取消", new DialogInterface.OnClickListener()  
        {  
            public void onClick(DialogInterface dialog, int id)  
            {  
                d.dismiss();  
            }  
        });  
        d = b.create();  
        d.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);  
        d.show();  
  
        WindowManager.LayoutParams lp = d.getWindow().getAttributes();  
        WindowManager wm = (WindowManager) context  
                .getSystemService(Context.WINDOW_SERVICE);  
        Display display = wm.getDefaultDisplay();  
        if (display.getHeight() > display.getWidth())  
        {  
            lp.width = (int) (display.getWidth() * 1.0);  
        }  
        else  
        {  
            lp.width = (int) (display.getWidth() * 0.5);  
        }  
        d.getWindow().setAttributes(lp);  
    }  

注意：增加权限  <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />