Progress in label - ios

Question

Use code for show downloading progress in percent
float progress = [[NSNumber numberWithInteger:totalBytesWritten] floatValue];
float total = [[NSNumber numberWithInteger: totalBytesExpectedToWrite] floatValue];
NSString *percentage = [NSString stringWithFormat:#"%d%%", (int)((progress/total)*100)];
[_label setText:[NSString stringWithFormat:#"%#%%", percentage]];
_label = [[UILabel alloc]initWithFrame:CGRectMake(323.43, 148.84, 42, 19)];
[_label setText: percentage];
_label.numberOfLines = 1;
_label.baselineAdjustment = UIBaselineAdjustmentAlignBaselines;
_label.adjustsFontSizeToFitWidth = YES;
_label.minimumScaleFactor = 10.0f/12.0f;
_label.clipsToBounds = YES;
_label.backgroundColor = [UIColor blackColor];
_label.textColor = [UIColor whiteColor];
_label.textAlignment = NSTextAlignmentCenter;
[self.view addSubview:_label];
If I use _label.backgroundColor = [UIColor blackColor]; progress label work correctly. But if I use _label.backgroundColor = [UIColor clearColor]; numbers superimposed on each other
Why?
_label.backgroundColor = [UIColor blackColor];
_label.backgroundColor = [UIColor clearColor];

Answer 1

You are adding multiples labels with the method [self.view addSubview: _label] If you want to see that more visually use the Debug View Hierarchy when you are debugging.
To solve the issue you can check if the _label is not nil and you will set only the text. See the code below:
float progress = [[NSNumber numberWithInteger:totalBytesWritten] floatValue];
float total = [[NSNumber numberWithInteger:totalBytesExpectedToWrite] floatValue];
NSString *percentage = [NSString stringWithFormat:#"%.f%%", ((progress / total) * 100)];
if (!_label) {
_label = [[UILabel alloc] initWithFrame:CGRectMake(323.43, 148.84, 42, 19)];
_label.numberOfLines = 1;
_label.baselineAdjustment = UIBaselineAdjustmentAlignBaselines;
_label.adjustsFontSizeToFitWidth = YES;
_label.minimumScaleFactor = 10.0f/12.0f;
_labellabel.clipsToBounds = YES;
_label.backgroundColor = [UIColor blackColor];
_label.textColor = [UIColor whiteColor];
_label.textAlignment = NSTextAlignmentCenter;
[self.view addSubview:_label];
}
_label.text = percentage;
Notice that you are trying to set the text before initialize it: [_label setText:[NSString stringWithFormat:#"%#%%", percentage]]; and if _label is nil the app crash in that point.
Try to avoid set the frame manually instead of that use auto layout.

Answer 2

You appear to be adding multiple labels [self.view addSubview: _label]. This code should only be executed once. With a black background you can only see the topmost label. With a clear background you can see them all

Answer 3

I think, the Label have overlapped. So you can use "tag" value to remove the label and recreated it every time.
Adding Tag
_label = [[UILabel alloc] initWithFrame:CGRectMake(323.43, 148.84, 42, 19)]; // after you will set the tag for the required Label.
_label.tag = 505;
Remove and recreate the label
[[self.view viewWithTag:505]removeFromSuperView]; // after you will create the Label
_label = [[UILabel alloc] initWithFrame:CGRectMake(323.43, 148.84, 42, 19)];