我现在的位置总是返回null。我该如何解决这个问题？ [英] My current location always returns null. How can I fix this?

问题描述

我想找到我的当前位置的机器人项目。当应用程序被加载我现在的位置总是空。我已经建立了在清单等权限，当我发现当前位置我打算用坐标找到距离到地图上的其他位置。我的code片段如下。为什么我总是得到一个空值？

  locMan =（LocationManager）getSystemService（Context.LOCATION_SERVICE）;
标准暴击=新标准（）;
塔= locMan.getBestProvider（暴击，假）;
位置= locMan.getLastKnownLocation（塔）;

如果（位置！= NULL）{
    的System.out.println（位置不为空！）;
    土地增值税=（INT）（location.getLatitude（）* 1E6）;
    隆基=（INT）（location.getLongitude（）* 1E6）;
    的GeoPoint ourLocation =新的GeoPoint（LATI，隆基）;
    OverlayItem overlayItem =新OverlayItem（ourLocation，第一串，
                                                            第2个字符串）;
    CustomPinpoint定制=新CustomPinpoint（D，MainMap.this）;
    custom.insertPinpoint（overlayItem）;
    overlayList.add（自定义）;
    overlayList.clear（）;
} 其他 {
   的System.out.println（定位为空！+塔）;
   Toast.makeText（MainMap.this，无法获得供应商，Toast.LENGTH_SHORT）
                                                                    。显示（）;
}
 

解决方案

getLastKnownLocation（）使用位置（S）$ P $其他应用程序pviously发现。如果没有应用程序已经做到了这一点，那么 getLastKnownLocation（）将返回null。

一件事，你可以做你的code有在得到的最后一个已知的位置 - 遍历所有已启用的提供者，而不仅仅是最佳供应商一个更好的机会。例如，

 私人地点getLastKnownLocation（）{
    名单＆LT;字符串＆GT;供应商= mLocationManager.getProviders（真正的）;
    位置bestLocation = NULL;
    对于（字符串提供商：提供商）{
        位置L = mLocationManager.getLastKnownLocation（供应商）;
        ALog.d（最后已知的位置，提供者：％S，位置：％s时，供应商，
                升）;

        如果（L == NULL）{
            继续;
        }
        如果（bestLocation == NULL
                || l.getAccuracy（）＆其中; bestLocation.getAccuracy（））{
            ALog.d（找到最佳的最后已知​​位置：％s的，L）;
            bestLocation =升;
        }
    }
    如果（bestLocation == NULL）{
        返回null;
    }
    返回bestLocation;
}
 

如果您的应用程序无法处理而无需一个位置，如果没有最后已知的位置，你需要监听位置更新。你可以看看这个类的一个实例，

  

<一个href="https://github.com/farble1670/autobright/blob/master/src/org/jtb/autobright/EventService.java">https://github.com/farble1670/autobright/blob/master/src/org/jtb/autobright/EventService.java

看方法 onStartCommand（），它会检查，如果网络提供商已启用。如果不是，则使用最后的已知位置。如果已启用，它会注册接收位置更新。

I am trying to find my current location for an android project. When the application is loaded my current location is always null. I have set up the permissions in the manifest etc. When I find the current location I intend to use the coordinates to find distances to other locations on the map. My code snippet is below. Why do I always get a null value?

locMan = (LocationManager) getSystemService(Context.LOCATION_SERVICE);          
Criteria crit = new Criteria();     
towers = locMan.getBestProvider(crit, false);
location = locMan.getLastKnownLocation(towers);    

if (location != null) {                 
    System.out.println("Location is not null!");
    lat = (int) (location.getLatitude() *1E6);
    longi = (int) (location.getLongitude() * 1E6);
    GeoPoint ourLocation = new GeoPoint(lati, longi);
    OverlayItem overlayItem = new OverlayItem(ourLocation, "1st String",
                                                            "2nd String");
    CustomPinpoint custom = new CustomPinpoint(d, MainMap.this);
    custom.insertPinpoint(overlayItem);
    overlayList.add(custom);
    overlayList.clear();
} else {
   System.out.println("Location is null! " + towers);
   Toast.makeText(MainMap.this, "Couldn't get provider",Toast.LENGTH_SHORT)
                                                                    .show();
}

解决方案

getLastKnownLocation() uses the location(s) previously found by other applications. if no application has done this, then getLastKnownLocation() will return null.

one thing you can do to your code to have a better chance at getting as last known location- iterate over all of the enabled providers, not just the best provider. for example,

private Location getLastKnownLocation() {
    List<String> providers = mLocationManager.getProviders(true);
    Location bestLocation = null;
    for (String provider : providers) {
        Location l = mLocationManager.getLastKnownLocation(provider);
        ALog.d("last known location, provider: %s, location: %s", provider,
                l);

        if (l == null) {
            continue;
        }
        if (bestLocation == null
                || l.getAccuracy() < bestLocation.getAccuracy()) {
            ALog.d("found best last known location: %s", l);
            bestLocation = l;
        }
    }
    if (bestLocation == null) {
        return null;
    }
    return bestLocation;
}

if your app can't deal without having a location, and if there's no last known location, you will need to listen for location updates. you can take a look at this class for an example,

https://github.com/farble1670/autobright/blob/master/src/org/jtb/autobright/EventService.java

see the method onStartCommand(), where it checks if the network provider is enabled. if not, it uses last known location. if it is enabled, it registers to receive location updates.

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