即使启用了 GPS，也无法获取位置

Posted 2023-04-14

【中文标题】即使启用了 GPS，也无法获取位置

【英文标题】：cannot get location even gps are enabled

【发布时间】：2020-04-01 15:08:07

【问题描述】：

我有一个使用多个位置提供程序来获取最新的已知位置信息的功能，但我发现这是不稳定的（至少在我的带有 android 7.1 的小米中，我仍然不知道在另一部手机上），这是我的功能：

private String getGPS() 
    LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    List<String> providers = lm.getProviders(false);

    /* Loop over the array backwards, and if you get an accurate location, then break                 out the loop*/
    Location l = null;

    for (int i=providers.size()-1; i>=0; i--) 
        l = lm.getLastKnownLocation(providers.get(i));
        if (l != null) break;
    

    String msg = "";
    if (l != null) 
        msg = l.getLatitude() + "|" + l.getLongitude();
    
    return msg;

【参考方案1】：

方法getLastKnownLocation() 仅在另一个应用程序最近请求它时才返回有效位置。

你应该这样做：

LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

//Avoid the for loop, in this way you can know where there's an issue, if there'll be

Location l = lm.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);

if (l== null)
    l = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);

if (l== null)
    l = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

那么，如果这三个都为null，则意味着没有应用程序在您之前请求位置，因此您必须自己进行请求： 您可以请求“位置更新”，因此您必须实现一个侦听器，如果需要，您可以将其插入到您的活动中，以这种方式：

class YourActivity extends Activity() implements LocationListener 

    private Location l;
    private LocationManager lm;

    @Override
    ... onCreate(...) 

        lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

        l = lm.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);

        if (l == null)
            l = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
        if (l == null)
            l = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

        if (l == null)  //If you need a real-time position, you should request updates even if the first location is not null
            //You don't need to use all three of these, check this answer for a complete explanation: https://***.com/questions/6775257/android-location-providers-gps-or-network-provider 

            lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 10 * 1000, 10F, this);
            lm.requestLocationUpdates(LocationManager.PASSIVE_PROVIDER, 10 * 1000, 10F, this);
            lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 10 * 1000, 10F, this); //This consumes a lot of battery

            //10 * 1000 is the delay (in millis) between two positions update
            //10F is the minimum distance (in meters) for which you'll have update
        
    

    @Override
    void onLocationChanged(Location location) 
        l = location;
    

    private String getGPS() 
        String msg = "";
        if (l != null) 
            msg = l.getLatitude() + "|" + l.getLongitude();
        
        return msg;
    

    //To avoid crash, you must remove the updates in onDestroy():
    @Override
    void onDestroy() 
        lm.removeUpdates(this)
        super.onDestroy()
    

Android 6+ 当然你必须插入应用内权限请求

【讨论】：

谢谢先生的回答，顺便说一句，lm.requestLocationUpdates 最后不会收到这个上下文，我如何在不实现 LocationListener 的情况下使用它

如果不想在Activity中设置，可以声明LocationListener类型的对象，但是没有监听器就不能请求更新

是的，先生，现在我使用requestSingleUpdate，因为 getGPS() 在 runnable 内部被调用，谢谢先生