制作視頻時顯示錄制計時器

Question

我已經實現了用於錄制視頻的 AVCaptureSession 的概念。

-(void)startRecordingWithOrientation:(AVCaptureVideoOrientation)videoOrientation 
{

    AVCaptureConnection *videoConnection = [AVCamUtilities   
                                           connectionWithMediaType:AVMediaTypeVideo  
                                           fromConnections:[[self movieFileOutput] connections]];
    if ([videoConnection isVideoOrientationSupported])
        [videoConnection setVideoOrientation:videoOrientation];

    [[self movieFileOutput] startRecordingToOutputFileURL:[self outputFileURL]  
    recordingDelegate:self];
 } 

它正在正確錄制視頻，但屏幕上沒有錄制計時器。 任何人都知道如何在制作視頻時顯示計時器。

提前致謝。

Answer 1

我在錄制時向顯示視頻的視圖中添加一個 UILabel 並使用此代碼顯示錄制時間

@property (weak, nonatomic) IBOutlet UILabel *labelTime;

@property(nonatomic, strong) NSTimer *timer;
@property(nonatomic) int timeSec;
@property(nonatomic) int timeMin;

//開始錄制的方法

- (void)startRecord {
    self.timeMin = 0;
    self.timeSec = 0;

    //String format 00:00
    NSString* timeNow = [NSString stringWithFormat:@"%02d:%02d", self.timeMin, self.timeSec];
    //Display on your label
    //[timeLabel setStringValue:timeNow];
    self.labelTime.text= timeNow;

    self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerTick:) userInfo:nil repeats:YES];
    [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSDefaultRunLoopMode];

    //Start recording
    [movieFileOutput startRecordingToOutputFileURL:outputURL recordingDelegate:self];

}


//Event called every time the NSTimer ticks.
- (void)timerTick:(NSTimer *)timer {
    self.timeSec++;
    if (self.timeSec == 60)
    {
        self.timeSec = 0;
        self.timeMin++;
    }
    //String format 00:00
    NSString* timeNow = [NSString stringWithFormat:@"%02d:%02d", self.timeMin, self.timeSec];
    //Display on your label
    self.labelTime.text= timeNow;
}

Answer 2

@Fran Martin 接受的答案效果很好！

因為我在Swift中使用它，所以我花了大約一個小時來找出正確的Timer()函數。 為了幫助下一個不熟練使用 Objective C 的人，這里是已接受答案的Swift版本，其中包含一些額外的功能來invalidate計時器invalidate將計時器重置回00:00 ，何時在viewWillAppear使用它，以及何時使用它invalidate

始終invalidate viewWillDisappear或viewDidDisappear的計時器invalidate ，否則如果它是repeat計時器並且它正在運行，您可能會出現memory leak

我遇到了一個無法預料的問題，即使我會停止它，計時器仍在運行，我發現這個SO Answer說你必須在再次啟動它之前停止它，並且當你聲明計時器使用weak

@IBOutlet weak fileprivate var yourLabel: UILabel!

var timeMin = 0
var timeSec = 0
weak var timer: Timer?

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    // if your presenting this vc yourLabel.txt will show 00:00
    yourLabel.txt = String(format: "%02d:%02d", timeMin, timeSec)
}

override func viewDidDisappear(_ animated: Bool) {
    super.viewDidDisappear(animated)

    resetTimerToZero()
}

// MARK:- recordButton
@IBAction fileprivate func recordButtonTapped(_ sender: UIButton) {

    startTimer()
    
    movieFileOutput.startRecording(to: videoUrl, recordingDelegate: self)
}

// MARK:- Timer Functions
fileprivate func startTimer(){
    
    // if you want the timer to reset to 0 every time the user presses record you can uncomment out either of these 2 lines

    // timeSec = 0
    // timeMin = 0

    // If you don't use the 2 lines above then the timer will continue from whatever time it was stopped at
    let timeNow = String(format: "%02d:%02d", timeMin, timeSec)
    yourLabel.txt = timeNow

    stopTimer() // stop it at it's current time before starting it again
    timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { [weak self] _ in
                self?.timerTick()
            }
}
    
@objc fileprivate func timerTick(){
     timeSec += 1
        
     if timeSec == 60{
         timeSec = 0
         timeMin += 1
     }
        
     let timeNow = String(format: "%02d:%02d", timeMin, timeSec)
        
     yourLabel.txt = timeNow
}

// resets both vars back to 0 and when the timer starts again it will start at 0
@objc fileprivate func resetTimerToZero(){
     timeSec = 0
     timeMin = 0
     stopTimer()
}

// if you need to reset the timer to 0 and yourLabel.txt back to 00:00
@objc fileprivate resetTimerAndLabel(){

     resetTimerToZero()
     yourLabel.txt = String(format: "%02d:%02d", timeMin, timeSec)
}

// stops the timer at it's current time
@objc fileprivate stopTimer(){

     timer?.invalidate()
}

Answer 3

記住開始錄制時的時間 (NSTimeInterval)，將其保存在實例變量中，然后在每秒觸發兩次左右的計時器中計算與當前時間的差異 (NSDate timeIntervalSinceReferenceDate)，並在 UITextView 中顯示結果時間？

為避免漂移，請在每次顯示后在計時器上設置“觸發時間”，並將其設置為距離下一整秒（或半秒或多長時間）的時間。 這樣，例如，如果顯示時間需要 0.1 秒，則下一次觸發時間更有可能在整整一秒左右。