Question

上班途中，我每隔1秒跟踪一次坐标。当我得到两点之间的距离，并在TextView中显示它时，我得到的数字比我应该高得多。例如，一条9.5英里的路线最终显示为14,000英里的球场。以下是我的代码的副本：

GPS更新处理程序/功能：

public void onGPSUpdate(Location location)
{
    //Get Milestone prefs
    SharedPreferences settings = getSharedPreferences("AppPrefs", 0);
    Integer milestone = settings.getInt("milestone", 5);

    //Get current Speed and Distance
    speed = location.getSpeed();

    Float newDistance;
    if(oldLocation == null){
        oldLocation = new Location("Point B");
        oldLocation = location;

        newDistance = 0f;
    } else {
        newDistance = getDistanceInMiles(location, oldLocation);
    }

    // Make sure the user is actually moving and that we have an old location
    // Add new distance to total
       if(roundDecimal(convertSpeed(speed),2) > 0 && oldLocation != null){
            distance = distance + newDistance;
       }

    // Format the distance to 1 decimal
    String formattedDistance = String.format("%.1f", distance);

    setText(R.id.miles_message, formattedDistance + " ");

}

计算里程数函数：

public float getDistanceInMiles(Location p1, Location p2){
    float[] distance1 = new float[1];

    Double latFn = p1.getLatitude();
    Double lonFn = p1.getLatitude();
    Double newLat = p2.getLatitude();
    Double newLon = p2.getLatitude();

    Location.distanceBetween(latFn,lonFn,newLat,newLon, distance1); //in meters
    float distanceInMeters = distance1[0];
    float distanceInMiles = distanceInMeters * 0.00062137f;
    return distanceInMiles; //in miles
}

有什么建议吗？

Answer 1

您的代码中存在错误。您将纬度用于每个点的经度和纬度。此外，还有一个内置的距离定位功能。尝试：

public float getDistanceInMiles(Location p1, Location p2){
    float distanceInMeters = p1.distanceTo(p2);
    float distanceInMiles = distanceInMeters * 0.00062137f;
    return distanceInMiles; //in miles
}

Answer 2

Gabe在我的代码中发现了一个错误。我为每个坐标使用getLatitude()而不是getLongitude()和getLatitude()。我也改变了他的getDistanceInMiles功能：

public float getDistanceInMiles(Location p1, Location p2){
    float distanceInMeters = p1.distanceTo(p2);
    float distanceInMiles = distanceInMeters * 0.00062137f;
    return distanceInMiles; //in miles
}

我找到的第二个错误是在我设置oldLocation的第一个条件声明中。 oldLocation仅在首次运行时设置，导致getdistanceInMiles()函数每次计算从起始坐标到当前坐标的距离，而不是最后一个坐标与当前坐标之间的距离。

以下是纠正后的代码片段：

public void onGPSUpdate(Location location)
{
    //Get Milestone prefs
    SharedPreferences settings = getSharedPreferences("AppPrefs", 0);
    Integer milestone = settings.getInt("milestone", 5);

    //Get current Speed and Distance
    speed = location.getSpeed();

    Float newDistance;
    if(oldLocation == null){
        oldLocation = new Location("Point B");
        oldLocation = location;

        newDistance = 0f;
    } else {
        newDistance = getDistanceInMiles(location, oldLocation);
        oldLocation = location; //Second correction, make sure to set last coordinates to current coordinates
    }

    // Make sure the user is actually moving and that we have an old location
    // Add new distance to total
       if(roundDecimal(convertSpeed(speed),2) > 0 && oldLocation != null){
            distance = distance + newDistance;
       }

        // Format the distance to 1 decimal
        String formattedDistance = String.format("%.1f", distance);

        setText(R.id.miles_message, formattedDistance + " ");

}

//First, simplified distance function to Gabe's suggestion
public float getDistanceInMiles(Location p1, Location p2){
    float distanceInMeters = p1.distanceTo(p2);
    float distanceInMiles = distanceInMeters * 0.00062137f;
    return distanceInMiles; //in miles
}

为什么我的Android应用程序中的GPS距离计算错误？

2 个答案: