将 String 转换为 Float 以移动 UISlider答案

【问题标题】：Convert String to Float to move UISlider将 String 转换为 Float 以移动 UISlider
【发布时间】：2016-12-26 11:31:32
【问题描述】：

如何将 JSON 数据的时间转换为浮点值。下面的代码用于将时间转换为浮点数，我将它作为音频的总长度传递给 UISlider。我想用那个时间跨度移动滑块

//Json Data
{
        duration = "00:03:45";
        id = 8;
}

//音频播放器侧边栏功能

 if(audioController.playbackState == MPMusicPlaybackStatePlaying){


    if (isSelected == YES) {
        currentAutio = audioList[selectedAudio];
    } else {
        currentAutio = audioList[0];
    }
    NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
    numberFormatter.numberStyle = NSNumberFormatterDecimalStyle;

    float value = [numberFormatter numberFromString:currentAutio.duration].floatValue;

    float currentPlaybackTime = [audioController currentPlaybackTime];
    float TotalLength = value;

    float remainingPlaybackTime = TotalLength - currentPlaybackTime;

    float sliderPosition = (currentPlaybackTime *100) / TotalLength;

    NSLog(@"current playbacktime %f",currentPlaybackTime);
    NSLog(@"TotalLength %f",TotalLength);
    NSLog(@"remainingPlaybackTime %f",remainingPlaybackTime);
    NSLog(@"sliderPosition %f",sliderPosition);

    //Update slider
    [progressSlider setValue:sliderPosition];

    //Update labels
    NSDate* d1 = [NSDate dateWithTimeIntervalSince1970:currentPlaybackTime];
    NSDate* d2 = [NSDate dateWithTimeIntervalSince1970:remainingPlaybackTime];

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"mm:ss"];

    NSString *currentTime = [dateFormatter stringFromDate:d1];
    NSString *ramainingTime = [dateFormatter stringFromDate:d2];

    [trackCurrentPlaybackTimeLabel setText:currentTime];
    [trackLengthLabel setText:[NSString stringWithFormat:@"-%@",ramainingTime]];

}

我得到以下输出：值 = 0.00000

【问题讨论】：

你期望从给定的3:45 得到什么 float 值？

标签： ios objective-c uislider

【解决方案1】：

我不认为有将时间间隔转换为浮点数的内置机制，但它很容易编写：

func timeIntervalFrom(_ timeString: String) -> TimeInterval? {
    //Add code to validate that string is in correct format
    let components = time.components(separatedBy: ":")
    guard components.count == 3, 
        let hours = Double(components[0]), 
        let minutes = Double(components[1]),
        let seconds = Double(components[2]) else {
            return nil
    }
    return hours * 3600 +  minutes * 60 + seconds
}

【讨论】：

【解决方案2】：

只需将duration 从字符串转换为整数组件。然后以秒为单位计算总时长。

你可以像这样简单地得到整数分量：

斯威夫特

let timeComponents = duration.components(separatedBy: ":")

目标 C

NSArray *timeComponents = [duration componentsSeparatedByString:@":"];

timeComponents[0] 将是小时部分。
timeComponents[1] 将是分钟部分。
timeComponents[2] 将是秒部分。

总秒数：（小时 * 60 * 60）+（分钟 * 60）+ 秒。

之后，调整滑动条的值会很容易:)

【讨论】：