iOS开发中有时候有这样的需求：当用户设置不允许访问照片、麦克风和相机等系统权限的时候，这时需要直接跳转到系统的隐私界面进行设置。
判断是否开启权限
前面已经说过，我们需要在用户不允许访问的时候跳转，那么首先我们就要判断一些是否已经开启系统相机权限了。
照片权限检测
需要：#import <AssetsLibrary/AssetsLibrary.h> //导入此类和AssetsLibrary.framework框架
代码如下：
int author = [ALAssetsLibrary authorizationStatus];
NSLog(@"author type:%d",author);
if(author == ALAuthorizationStatusRestricted || author == ALAuthorizationStatusDenied) {
// The user has explicitly denied permission for media capture.
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"无法使用相册"
message:@"请在iPhone的"设置-隐私-照片"中允许访问照片。"
delegate:self
cancelButtonTitle:@"确定"
otherButtonTitles:nil];
[alert show];
return;ALAssetsLibrary类
ALAssetsLibrary类是代表系统中整个资源库，使用它可以访问资源库中的资源和保存照片，视频等功能。
//判断当前应用是否能访问相册资源
/*
typedef NS_ENUM(NSInteger, ALAuthorizationStatus) {
ALAuthorizationStatusNotDetermined = 0, 用户尚未做出了选择这个应用程序的问候
ALAuthorizationStatusRestricted, 此应用程序没有被授权访问的照片数据。可能是家长控制权限。
ALAuthorizationStatusDenied, 用户已经明确否认了这一照片数据的应用程序访问.
ALAuthorizationStatusAuthorized 用户已授权应用访问照片数据.
}
*/访问摄像头
需要：#import <AVFoundation/AVFoundation.h>
代码如下：
if(isIOS7AndLater) {
NSString *mediaType = AVMediaTypeVideo;// Or AVMediaTypeAudio
AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:mediaType];
NSLog(@"---cui--authStatus--------%d",authStatus);
// This status is normally not visible—the AVCaptureDevice class methods for discovering devices do not return devices the user is restricted from accessing.
if(authStatus ==AVAuthorizationStatusRestricted){
NSLog(@"Restricted");
}else if(authStatus == AVAuthorizationStatusDenied){
// The user has explicitly denied permission for media capture.
NSLog(@"Denied"); //应该是这个，如果不允许的话
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示"
message:@"请在设备的"设置-隐私-相机"中允许访问相机。"
delegate:self
cancelButtonTitle:@"确定"
otherButtonTitles:nil];
[alert show];
return;
}
else if(authStatus == AVAuthorizationStatusAuthorized){//允许访问
// The user has explicitly granted permission for media capture, or explicit user permission is not necessary for the media type in question.
NSLog(@"Authorized");
}else if(authStatus == AVAuthorizationStatusNotDetermined){
// Explicit user permission is required for media capture, but the user has not yet granted or denied such permission.
[AVCaptureDevice requestAccessForMediaType:mediaType completionHandler:^(BOOL granted) {
if(granted){//点击允许访问时调用
//用户明确许可与否，媒体需要捕获，但用户尚未授予或拒绝许可。
NSLog(@"Granted access to %@", mediaType);
}
else {
NSLog(@"Not granted access to %@", mediaType);
}
}];
}else {
NSLog(@"Unknown authorization status");
}
}麦克风权限检测
代码如下：
//检测麦克风功能是否打开
[[AVAudioSessionsharedInstance]requestRecordPermission:^(BOOL granted) {
if (!granted)
{
[ViewUtilalertViewWithString:NSLocalizedString(@"麦克风功能未开启",nil)];
}
else
{
[selfrecord:sender];
}
}];如何跳转到系统设置界面
判断权限是否设置之后就可以在相应的代理方法进行界面跳转了，那么如何进行跳转呢？
首先要在项目中的info.plist中添加 URL types 并设置一项URL Schemes为prefs，如下图：
实现代码如下：
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:url]];//url为具体路径以下是跳转到一些常用界面的代码
隐私->照片界面
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"prefs:root=Privacy&path=PHOTOS"]];隐私->相机界面
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"prefs:root=Privacy&path=CAMERA"]];蓝牙设置界面
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"prefs:root=Bluetooth"]];其他界面参数配置
About — prefs:root=General&path=About
Accessibility — prefs:root=General&path=ACCESSIBILITY
Airplane Mode On — prefs:root=AIRPLANE_MODE
Auto-Lock — prefs:root=General&path=AUTOLOCK
Brightness — prefs:root=Brightness
Bluetooth — prefs:root=General&path=Bluetooth
Date & Time — prefs:root=General&path=DATE_AND_TIME
FaceTime — prefs:root=FACETIME
General — prefs:root=General
Keyboard — prefs:root=General&path=Keyboard
iCloud — prefs:root=CASTLE
iCloud Storage & Backup — prefs:root=CASTLE&path=STORAGE_AND_BACKUP
International — prefs:root=General&path=INTERNATIONAL
Location Services — prefs:root=LOCATION_SERVICES
Music — prefs:root=MUSIC
Music Equalizer — prefs:root=MUSIC&path=EQ
Music Volume Limit — prefs:root=MUSIC&path=VolumeLimit
Network — prefs:root=General&path=Network
Nike + iPod — prefs:root=NIKE_PLUS_IPOD
Notes — prefs:root=NOTES
Notification — prefs:root=NOTIFICATIONS_ID
Phone — prefs:root=Phone
Photos — prefs:root=Photos
Profile — prefs:root=General&path=ManagedConfigurationList
Reset — prefs:root=General&path=Reset
Safari — prefs:root=Safari
Siri — prefs:root=General&path=Assistant
Sounds — prefs:root=Sounds
Software Update — prefs:root=General&path=SOFTWARE_UPDATE_LINK
Store — prefs:root=STORE
Twitter — prefs:root=TWITTER
Usage — prefs:root=General&path=USAGE
VPN — prefs:root=General&path=Network/VPN
Wallpaper — prefs:root=Wallpaper
Wi-Fi — prefs:root=WIFI
来源：http://www.jianshu.com/p/1fb3f60b689a 简书作者：小球why