调用函数“didUpdateToLocation”而不进行更改答案

【问题标题】：Function "didUpdateToLocation" being called without changes调用函数“didUpdateToLocation”而不进行更改
【发布时间】：2012-09-28 04:03:55
【问题描述】：

我这样初始化 locationManager：

if (!self.locManager) 
{
    self.locManager = [[CLLocationManager alloc] init];
    self.locManager.delegate = self;
    [locManager startMonitoringSignificantLocationChanges];
}

我的设备没有移动，并且每次都在调用“didUpdateToLocation”。可能是什么问题？谢谢

【问题讨论】：

标签： iphone ios location mkmapview cllocationmanager

【解决方案1】：

didUpdateToLocation 可能会因多种原因而更新，处理此问题的一个好策略是根据时间戳逐步过滤结果，然后根据要求的准确性。

苹果在LocateMe sample app中提供了一个很好的例子：

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    // test the age of the location measurement to determine if the measurement is cached
    // in most cases you will not want to rely on cached measurements
    NSTimeInterval locationAge = -[newLocation.timestamp timeIntervalSinceNow];
    if (locationAge > 5.0) return;

    // test that the horizontal accuracy does not indicate an invalid measurement
    if (newLocation.horizontalAccuracy < 0) return;

    // test the measurement to see if it is more accurate than the previous measurement
    if (self.bestEffortAtLocation == nil || self.bestEffortAtLocation.horizontalAccuracy > newLocation.horizontalAccuracy)
    {
        // store the location as the "best effort"
        self.bestEffortAtLocation = newLocation;

        // test the measurement to see if it meets the desired accuracy
        //
        // IMPORTANT!!! kCLLocationAccuracyBest should not be used for comparison with location coordinate or altitidue 
        // accuracy because it is a negative value. Instead, compare against some predetermined "real" measure of 
        // acceptable accuracy, or depend on the timeout to stop updating. This sample depends on the timeout.
        //
        if (newLocation.horizontalAccuracy <= locationManager.desiredAccuracy) {
            // we have a measurement that meets our requirements, so we can stop updating the location
            // 
            // IMPORTANT!!! Minimize power usage by stopping the location manager as soon as possible.
            //
            [self stopUpdatingLocation:NSLocalizedString(@"Acquired Location", @"Acquired Location")];
        }
    }
}

【讨论】：

谢谢，但如果我希望定位服务保持打开状态怎么办？ stopUpdating 可能会停止位置管理器吗？
此代码允许位置管理器根据需要经常更新，以将用户定位到所需的准确性。此时，电源管理停止更新是礼貌和明智的。如果您的应用需要在用户更改位置时对其进行监控，那么您可以注册重大更改：[locationManager startMonitoringSignificantLocationChanges]; 请参阅docs

【解决方案2】：

您是否检查位置差异？ CoreLocation 也会在精度、航向或速度等其他属性发生变化时调用回调

startMonitoringSignificantLocationChanges应该给你一个初始修复，然后你会收到“重大变化”的回调（蜂窝塔变化等）

【讨论】：

对不起，我没有完全理解。