IOS Augmented Reality增强现实学习笔记 -基于位置

本文主要是介绍IOS Augmented Reality增强现实学习笔记 -基于位置，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

地图编程和定位是增强现实技术的基础，因此首先学习Location Services
1标准定位(standard location service)
有两种方式可以监控我们的位置，首先是标准定位。这是一种很普遍的方式，因为所有的ios设备都支持标准定位。首先我们要导入Core Location Framework到我们的工程中，然后把Core Location Framework加入到头文件中,如下所示：

#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>
@interface FirstViewController : UIViewController <CLLocationManagerDelegate> {UITextView *locationTextView;
}
@property (nonatomic, retain) IBOutlet UITextView *locationTextView;
@end
CLLocationManagerDelegate 会将定位信息传给locationManager:didUpdateToLocation:fromLocation: 方法，如果发生错误则会传给
locationManager:didFailWithError: 方法，将这些方法的实现加入到.m文件中

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation*)newLocation
fromLocation:(CLLocation *)oldLocation{

//Apple建议检查新位置的时间戳，因为有时调用代理方法会有延迟
NSDate* eventDate = newLocation.timestamp; NSTimeInterval howRecent = [eventDate timeIntervalSinceNow];if (abs(howRecent) < 15.0) {

locationTextView.text = [NSString stringWithFormat:@"latitude %+.6f, longitude%+.6f\n",
newLocation.coordinate.latitude,newLocation.coordinate.longitude];
}else{

locationTextView.text = @"Update was old";

}
}

ok,现在让我们实现启动服务的方法

- (void)startStandardUpdates{
CLLocationManager *locationManager = [[CLLocationManager alloc] init];locationManager.delegate = self;
locationManager.desiredAccuracy = kCLLocationAccuracyKilometer;
locationManager.distanceFilter = 500;
[locationManager startUpdatingLocation];
}
最后我们在viewDidLoad方法中调用 startStandUpdates方法

- (void)viewDidLoad{
[self startStandardUpdates];
[super viewDidLoad];
}
这样运行就可以获取到latitude和longitude信息了
1显著位置变化定位(significant-change location service)
从iOS 4.0之后新加入了significant-change location service服务,它更省电，但是精确度会差一些。
它使用cellular radio代替GPS radio来定位.
使用的方式和标准定位很相似，它也会调用delegate的locationManager:didUpdateToLocation:fromLocation: 方法来传递位置信息。下面是启动significant-change location service的方法:
- (void)startSignificantChangeUpdates {
CLLocationManager *locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self; [locationManager startMonitoringSignificantLocationChanges];
}
然后在viewDidLoad方法中加入调用：
- (void)viewDidLoad{
//[self startStandardUpdates];
[self startSignificantChangeUpdates];
[super viewDidLoad];
}
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两种位置定位总结完后，下面学习地理位置监控服务(Geographic Region Monitoring Service),即当我们进入某一个区域后，系统会识别到,并调用didEnterRegion和didExitRegion方法来处理事件。直接上代码：
- (void)startRegionMonitoring {
NSLog(@"Starting region monitoring"); CLLocationManager *locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self;
CLLocationCoordinate2D coord = CLLocationCoordinate2DMake(37.787359, -122.408227);
CLRegion *region = [[CLRegion alloc] initCircularRegionWithCenter:coord radius:1000.0 identifier:@"San Francisco"];
[locationManager startMonitoringForRegion:region desiredAccuracy:kCLLocationAccuracyKilometer];

 }
此方法设置(37.787359, -122.408227)为中心，半径1000米的范围为检测区域.之后我们就可以实现didEnterRegion和dieExitRegion方法完成对于进入区域和离开区域的事件的处理了：
- (void)locationManager:(CLLocationManager *)manager didEnterRegion:(CLRegion *)region {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"区域检测"
message:@"你进入此区域"
delegate:self
cancelButtonTitle:@"OK"
otherButtonTitles:nil, nil];
[alert show];
[alert release];
}
- (void)locationManager:(CLLocationManager *)manager didExitRegion:(CLRegion *)region {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Region Alert"
message:@"你离开此区域"
delegate:self
cancelButtonTitle:@"OK"
otherButtonTitles:nil, nil];
[alert show];
[alert release];
}
最后一步，即在viewDidLoad中调用startRegionMonitoring方法
- (void)viewDidLoad {
[self startStandardUpdates]; //[self startSignificantChangeUpdates];
if ([CLLocationManager regionMonitoringAvailable]) { // 检查服务是否可用
[self startRegionMonitoring];
} // else do something
[super viewDidLoad];
}
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本帖最后讲述如何计算改变的距离。此方法只需要将前面standard location service中的方法做稍许改变即可
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{  NSDate* eventDate = newLocation.timestamp; NSTimeInterval howRecent = [eventDate timeIntervalSinceNow];
if (abs(howRecent) < 15.0){
//locationTextView.text = [NSString stringWithFormat:@"latitude %+.6f, longitude %+.6f\n",newLocation.coordinate.latitude, newLocation.coordinate.longitude];
CLLocationDistance dist=[newLocation distanceFromLocation:oldLocation]/1000;
locationTextView.text=[NSString stringWithFormat:@"distance %5.1f traveled"];
}else{
locationTextView.text = @"Update was old";
}
}
这样即可获取到位置的改变值了。