Question

我在我的一个应用程序中遇到NullPointerException。我以为我在这段代码中为Null引用占了所有位置，但似乎我可能错过了一些东西。我一直看着代码，但我仍然不确定这个NullPointerException是从哪里抛出来的。

这是用户报告的错误，所以我无法调试，也没有在开发过程中遇到此错误

代码/应用程序中发生了什么：

用户启动应用程序，我尝试通过NETWORK或GPS获取他们最后的已知位置。一旦我设置了位置，如果可用，我稍后会获取该位置的天气并将其显示给用户。

有没有人知道在这段代码中哪些可能会失败？我还应该对GPS / NETWORK进行一些进一步的检查吗？非常感谢任何帮助！

堆栈跟踪

java.lang.NullPointerException
at com.hookedroid.fishingcompanion.BaseActivity.getLastKnownLocation(BaseActivity.java:337)
at com.hookedroid.fishingcompanion.BaseActivity.getWeatherbyCurrent(BaseActivity.java:164)
at com.hookedroid.fishingcompanion.BaseActivity.getWeather(BaseActivity.java:138)
at com.hookedroid.fishingcompanion.MainFish.syncWeather(MainFish.java:214)
at com.hookedroid.fishingcompanion.MainFish.run(MainFish.java:206)
at java.lang.Thread.run(Thread.java:1019)

有问题的代码

// Gets the user's current NETWORK/GPS location
// then gets weather for that location
private void getWeatherbyCurrent() throws WeatherException {
    Criteria criteria = new Criteria();
    locationProvider = locManager.getBestProvider(criteria, true);

    // Error is thrown on this method call
    getLastKnownLocation();

    getLocationBasedWeather();
}

public void getLastKnownLocation() throws WeatherException {
    String provider;
    //Check if NETWORK Provider is enabled.  If enabled, get it's last known location.
    //If location is received, set baseLocation and return back to get weather.
    //If location is not received, continue on and try to get location from GPS Provider.
    if (isNetworkProviderEnabled()) {
        provider = LocationManager.NETWORK_PROVIDER;
        baseLocation = locManager.getLastKnownLocation(provider);
        // This is Line 337.  I had removed it from the posted code as it was unused
        // and didn't think it was causing an issue.  
        long fixTime = baseLocation.getTime();

        //Location returned from NETWORK_PROVIDER, return/stop executing code and get weather for this location
        if (baseLocation != null)
            return;
    }
    if (baseLocation == null && isGPSEnabled()) {
        provider = LocationManager.GPS_PROVIDER;
        baseLocation = locManager.getLastKnownLocation(provider);
    }
    else {
        if (locationProvider == null) {
            Criteria criteria = new Criteria();
            criteria.setAccuracy(Criteria.ACCURACY_COARSE);
            locationProvider = locManager.getBestProvider(criteria, true);
        }

        if (locationProvider != null)
            baseLocation = locManager.getLastKnownLocation(locationProvider);
        else {
            if (!isGPSEnabled && !isNetworkProviderEnabled)
                throw new WeatherException("No Location Providers are available.");
        }
    }
}
//Returns whether or not the NETWORK_PROVIDER is enabled
public boolean isNetworkProviderEnabled() {
    checkNetworkProvider();
    return this.isNetworkProviderEnabled;
}

//Check if the NETWORK_PROVIDER is enabled
public void checkNetworkProvider() {
    isNetworkProviderEnabled = locManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
}
//Returns whether or not the GPS_PROVIDER is enabled
public boolean isGPSEnabled() {
    checkGPS();
    return this.isGPSEnabled;
}
//Check if the GPS_PROVIDER is enabled
public void checkGPS() {
    isGPSEnabled = locManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
}

Answer 1

如果没有对代码进行过多分析，是否会出现权限问题？也许您的应用不允许使用GPS数据，这会导致意外错误？

-Woody

Answer 2

我没看到您注册位置更新的位置？也许这就是你在这里所缺少的。

Answer 3

我在发布之前不小心从我的代码中删除了一行，因为我原以为它只是一行未使用的代码。然而，它引起了这个问题。在以下行中，如果用户禁用了NETWORK_PROVIDER，则baseLocation将等于null。

long fixTime = baseLocation.getTime();

修复：不要尝试在Null位置对象上调用方法getTime（）:)谢谢大家！

获取最后已知位置的Android Mystery NullPointerException

3 个答案: