java - 将位置API与LBS JSR-179和JSR-179 Extended一起使用时，城市名称的空指针异常

我是BlackBerry OS开发的新手，我的代码尝试在传递LocationProvider参数后使用Criteria时获取城市名称。
我根据RIM本身的link进行了跟踪，我尝试了“ JSR-179”和“ JSR-179扩展”
我的代码如下：

“使用JSR 179”

public String CurrentLocation()
    {
        try
        {
            //LBS(Location Based Service) JSR-179
            Criteria criteria = new Criteria();
            criteria.isAddressInfoRequired();
            criteria.setCostAllowed(false);
            criteria.setAddressInfoRequired(true);
            criteria.setHorizontalAccuracy(200);
            criteria.setVerticalAccuracy(200);

            locationProvider = LocationProvider.getInstance(criteria);

            location = locationProvider.getLocation(10);
            cityName = location.getAddressInfo().getField(AddressInfo.CITY);
        }
        catch (LocationException le)
        {
            new Tracer("CurrentLocation() caught LocationException : " + le.getMessage());
            le.printStackTrace();
        }
        catch (InterruptedException ire)
        {
            new Tracer("CurrentLocation() caught InterruptedException: " + ire.getMessage());
            ire.printStackTrace();
        }
        return cityName;
    }

与JSR-179扩展

public String CurrentLocaiton(){
        try
        {
            BlackBerryCriteria BBCriteria = new BlackBerryCriteria();
            BBCriteria.setAddressInfoRequired(ProvideAddressInfoTExt);
            BBCriteria.setAltitudeRequired(true);
            BBCriteria.setSatelliteInfoRequired(true, true);
            BBCriteria.setCostAllowed(true);
            BBCriteria.setPreferredPowerConsumption(BlackBerryCriteria.POWER_USAGE_HIGH); //testing for high power

            BlackBerryLocationProvider bbLocationProvider
                                                = (BlackBerryLocationProvider)
                                                    BlackBerryLocationProvider.getInstance(BBCriteria);
            location = bbLocationProvider.getLocation(9000);
            QualifiedCoordinates qualCoor = location.getQualifiedCoordinates();
            cityName = location.getAddressInfo().getField(AddressInfo.CITY);
        }
        catch(LocationException le)
        {
            le.printStackTrace();
            System.out.println(le.getMessage());
        }
        catch(InterruptedException ie)
        {
            ie.printStackTrace();
            System.out.println(ie.getMessage());
        }
        catch(NullPointerException npe)
        {
            npe.printStackTrace();
            cityName = "Caught Null Pointer";
            Dialog.alert(npe.getMessage());
        }
        return cityName;
    }

我是在那里错过了什么东西还是有什么问题我已经在这个问题上待了好几个小时了。
我也尝试从此代码段中捕获Null Pointer Exception，如果从“ static void main”捕获，则Uncaught Exception: pushModalScreen called by a non-event thread

        ....
        try{
            String location = cellLocation.CurrentLocation();
            LabelField towerlocationText = new LabelField(towerString + location,
                                LabelField.FOCUSABLE|LabelField.DEFAULT_POSITION);
            add(towerlocationText);
        }
        catch(NullPointerException npe)
        {
            npe.printStackTrace();
            System.out.println(npe.getMessage());
            Dialog.alert(npe.getMessage() + "" + "AddresInfo/LocationProvider/Locaiton gave null pointer exception" );
        }
        ...

在BB-9700 BB-9790设备上以及在模拟器BB-9900上尝试过

谢谢，

最佳答案

use
Either :-
/***/
      UiApplication.getUiApplication().invokeLater(new Runnable()
        {
            public void run()
            {
                Dialog.alert("Hello");
            }
        });
/***/
or
        synchronized (UiApplication.getEventLock())
        {
                    Dialog.alert("Hello");
        }

无论您试图在非事件线程上显示Dialog的哪个位置，都需要一个事件锁。
您可以使用上述方法进行事件锁定
阅读article以获得更多信息。