A simple timer.

Define a global time variable

Nstimer *_timer;

Create a time variable and invoke the Timer method

-(void) viewdidload

{

[Super Viewdidload];

_timer = [Nstimer scheduledtimerwithtimeinterval:1 target:self selector: @selector (timeclick) Userinfo:nil Repeats:YES ];

[_timer firedate];//Start timer

}

#pragma mark-Countdown to exam time

-(void) Timeclick

{

timeout-= 1;

Nsinteger hour = timeout/3600;

Nsinteger minutes = (timeout/60)% 60;

Nsinteger seconds = timeout% 60;

NSString *strtime = [NSString stringwithformat:@ "%.2ld:%.2ld:%.2ld", (long) hour, (long) minutes, (long) seconds];

[Rightbutton settitle:strtime Forstate:uicontrolstatenormal];

if (Timeout <= 0)

{

[_timer setfiredate:[nsdate distantfuture];

[Self showalertview:@ "test time has arrived"];

}

}

-(void) method{

if (_isclick)

{//start

if ([_timer isValid])

{

[_timer invalidate];

_timer = nil;

Label.text = @ "Start";

_isclick = NO;

}

}

Else

{//Pause

Invalidate and re-create the time, the counter is counted from the attribute value, because the attribute holds the hedging

_timer = [Nstimer scheduledtimerwithtimeinterval:1 target:self selector: @selector (timeclick) Userinfo:nil Repeats:YES ];

[_timer Firedate];

Label.text = @ "Pause";

_isclick = YES;

}

}

A simple timer.