UISlider not updating

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I am trying to code a music player for an assignment and I am stuck with trying to get the slider to update as the song is playing. I have been able to make it so that if the user were to slide the slider the song will rewind/fast-forward to that part of the song. Does anyone know why the slider doesn't continuously update as the song is playing?

Here is the .h file

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
#import <MediaPlayer/MediaPlayer.h>

@interface AS3MPViewController : UIViewController <MPMediaPickerControllerDelegate>{
    IBOutlet UIButton *playButton;
    IBOutlet UIButton *stopButton;
    IBOutlet UIButton *pauseButton;
    IBOutlet UISlider *volumeSlider;
    AVAudioPlayer *musicPlayer;
    IBOutlet UIButton *pickSongButton;
    IBOutlet UISlider *timeSlider;
    NSTimer *timer;

@property (nonatomic, retain) UIButton *playButton;
@property (nonatomic, retain) UIButton *stopButton;
@property (nonatomic, retain) UIButton *pauseButton;
@property (nonatomic, retain) UISlider *volumeSlider;
@property (nonatomic, retain) AVAudioPlayer *musicPlayer;
@property (nonatomic, retain) UIButton *pickSongButton;
@property (nonatomic, retain) UISlider *timeSlider;
@property (nonatomic, retain) NSTimer *timer;

- (IBAction) play;
- (IBAction) stop;
- (IBAction) pause;
- (IBAction) changeVolume: (UISlider *)sender;
- (IBAction) chooseSong: (UIButton *)sender;
- (IBAction) changeTime: (UISlider *)sender;
- (void)setTimeSliderOptions;


Here is the .m file

#import "AS3MPViewController.h"

@interface AS3MPViewController ()


@implementation AS3MPViewController

@synthesize playButton = _playButton;
@synthesize stopButton = _stopButton;
@synthesize pauseButton = _pauseButton;
@synthesize musicPlayer = _musicPlayer;
@synthesize volumeSlider = _volumeSlider;
@synthesize pickSongButton = _pickSongButton;
@synthesize timeSlider = _timeSlider;
@synthesize timer;

- (void)viewDidLoad
    [super viewDidLoad];

    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"animals001"     ofType:@"mp3"];

    NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:filePath];

    self.musicPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:nil];

    [self.musicPlayer prepareToPlay];

- (void)didReceiveMemoryWarning
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.

- (IBAction) play {
    [self.musicPlayer play];


- (IBAction) stop {
    [self.musicPlayer stop];
    self.musicPlayer.currentTime = 0;

- (IBAction) pause {
    [self.musicPlayer pause];

- (IBAction) changeVolume: (UISlider *)sender {
    self.musicPlayer.volume = [sender value];

- (IBAction)chooseSong:(UIButton *)sender {
    MPMediaPickerController *mediaPicker = [[MPMediaPickerController alloc] initWithMediaTypes:MPMediaTypeAnyAudio];

    [mediaPicker setDelegate:self];
    [mediaPicker setAllowsPickingMultipleItems:NO];

    mediaPicker.prompt = NSLocalizedString(@"Add Some Songs To Play", "Prompt In Media Item Picker");

    [self presentModalViewController: mediaPicker animated:YES];

- (void) mediaPickerDidCancel:(MPMediaPickerController *)mediaPicker {
[self dismissModalViewControllerAnimated:YES];

- (void) mediaPicker:(MPMediaPickerController *)mediaPicker didPickMediaItems:    (MPMediaItemCollection *)mediaItemCollection {

    MPMediaItem *item = [[mediaItemCollection items] objectAtIndex:0];
    NSURL *url = [item valueForProperty:MPMediaItemPropertyAssetURL];

    //AVPlayerItem *playerItem = [[AVPlayerItem alloc] initWithURL:url];
    //AVPlayer *player = [[AVPlayer alloc] initWithPlayerItem:playerItem];

    self.timeSlider.maximumValue = [self.musicPlayer duration];

    self.musicPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:nil];

    [self.musicPlayer play];

    timer = [NSTimer scheduledTimerWithTimeInterval:0.1f target:self selector:@selector(songCurrentTime) userInfo:nil repeats:YES];

    [self dismissModalViewControllerAnimated:YES];

- (IBAction)changeTime: (UISlider *)sender {
    self.musicPlayer.currentTime = self.musicPlayer.duration * sender.value;

- (void)songCurrentTime {
    timeSlider.value = (self.musicPlayer.currentTime / self.musicPlayer.duration);

check in the connections that you are connected the IBAction method with slider with ValueChanged EX:

- (IBAction)changeTime: (UISlider *)sender {

check whether this method is connected with ValueChanged while IB connection

UISlider not updating current value in Swift, You can do it as you have using some tricks, first of all you need to set the target for the UISlider as some as suggested, the other point is get� Options that can not be updated will be ignored without errors. The value null can be used to unset a previously set value. The 'update' event fires after updating the slider. By default, the sliders values remain unchanged. To update the slider values, newOptions may also contain a start property that matches the signature of the .set() method.

I think your problem is that you are updating the value of the slider from a thread other than the main one. Try modifying the songCurrentTime method so that it calls another one on the main thread that updates the value of the slider.

- (void)songCurrentTime {
[self performSelectorOnMainThread:@selector(songCurrentTimeMain) withObject:nil waitUntilDone:YES];

- (void)songCurrentTimeMain {
timeSlider.value = (self.musicPlayer.currentTime / self.musicPlayer.duration);

Of course to get correct results make sure the minimum value of the slider is 0 and the maximum is 1.

Best Regards

UISlider, As you move the thumb of a slider, it passes its updated value to any actions attached to it. Use either a custom tint color or a custom image, but not both. Objective-C. Declare a slider property in the ViewController.h or in the interface of ViewController.m. @property (strong, nonatomic)UISlider *slider; //Define frame of slider and add to view CGRect frame = CGRectMake(0.0, 100.0, 320.0, 10.0); UISlider *slider = [[UISlider alloc] initWithFrame:frame]; [slider addTarget:self action:@selector(sliderAction:) forControlEvents

I've done something similar within this tutorial and the way I added a slider was the same as you did except for the fact that I used


as a value to assign to the slider.

It may be that the result of (self.musicPlayer.currentTime / self.musicPlayer.duration) is an inaccurate assignment to your slider value.

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When you set your slider value, the value is always less than or equal to 1 because self.musicPlayer.currentTime is always less than or equal to self.musicPlayer.duration. Instead, try this

timeSlider.value = self.musicPlayer.currentTime;

UISlider Tutorial and Example (Updated for 2018), Actual outcome: The slider handle does not move. It stays to the left. They all used to work, and they all still work on Android. I note, that the "value� Major tick mark locations, specified as a vector of numeric values or an empty vector. If you do not want to show major tick marks, specify this property as an empty vector. Tick locations that are outside the range of the Limits property do not display. MATLAB removes duplicate tick values.

timeSlider and self.timeSlider are not the same thing. Most of the iVars that you have declared are unnecessary (and misleading) because you synthesize your properties using the underscore form of the property name. For example, you have a timeSlider property that's backed by a _timeSlider iVar, and a timeSlider iVar that's a different thing entirely.

Use self.timeSlider.value = ....

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  • As I read it, the docs seem to say that the player updates its own currentTime as it plays. No?
  • You're right, my mistake. I think I found the issue and edited my answer.
  • Thank you for the suggestions but I've tried that without any luck. I've tried to set the value to 0 and the maximumValue to the length of the song and then changed the update function as you posted but it still doesn't update for some reason.