IOS在後臺每隔一段時間執行一下
阿新 • • 發佈：2018-12-31
步驟：
1.在info.plist里加入UIBackgroundModes鍵，其值為陣列，陣列之一為voip字串：
<key>UIBackgroundModes</key><array><string>voip</string></array>
2.在程式啟動的時候呼叫- (void)setupBackgroundHandler函式，函式體如下：
#pragma
mark - VoIP
-
(void)setupBackgroundHandler
{
if(
UIUDeviceIsBackgroundSupported() ){
if(
[[UIApplication
sharedApplication] setKeepAliveTimeout:600 handler: ^
{
[self requestServerHowManyUnreadMessages];
}
]
)
{
UDLog(@"Set
Background handler successed!");
}
else
{//failed
UDLog(@"Set
Background handler failed!");
}
}
else
{
UDLog(@"This
Deviece is not Background supported.");
}
}
-
(void)requestServerHowManyUnreadMessages
{
UIApplication*
app = [UIApplication sharedApplication];
if([app
applicationState] == UIApplicationStateBackground)
{
NSArray *
oldNotifications = [app scheduledLocalNotifications];
if ([oldNotifications
count] > 0)
[app
cancelAllLocalNotifications];UILocalNotification*
alarm = [[[UILocalNotification alloc] init] autorelease];
if (alarm)
{
alarm.fireDate
= [NSDate dateWithTimeIntervalSinceNow:15];
alarm.timeZone
= [NSTimeZone defaultTimeZone];
alarm.repeatInterval
= 0;
alarm.soundName
= UILocalNotificationDefaultSoundName;
alarm.alertBody
= @"Time
to request MOA2 Server!";
[app
scheduleLocalNotification:alarm];
}
}
else if([app
applicationState] == UIApplicationStateActive)
{
UIAlertView
*alertView = [[[UIAlertView alloc] init] autorelease];
[alertView
setTitle:@"alert"];
[alertView
setMessage:@"Time
to request MOA2 Server!"];
[alertView
addButtonWithTitle:NSLocalizedString(@"cancel",
nil)];
[alertView
setDelegate:nil];
[alertView
show];
}
}
|
解說：
- (BOOL)setKeepAliveTimeout:(NSTimeInterval)timeout handler:(void (^)(void))keepAliveHandler
函式功能：app每隔timeout喚醒一次。
0.要成功呼叫該函式，就必須在Info.plist裡設UIBackgroundModes鍵的array值之一voip字串.
1.timeout必須>=600
2.喚醒app的時間間隔是不精準的。
3.喚醒後只有10秒執行時間。即handler裡的程式碼要在10秒類執行完。10秒後app再次被阻塞。
（可以用-backgroundTimeRemaining屬性來返回剩餘時間）
4.該函式成功呼叫後，在程式生命週期內有效。
該函式的效果在回到前臺的狀況下,依然有效。（因此可以把它當timer使.）
5.clearKeepAliveTimeout函式用來清除handler。