UISlider 成为 UIView 其他 self.view 的子视图时将不起作用

UISlider won#39;t work when it becomes a subview of a UIView other self.view(UISlider 成为 UIView 其他 self.view 的子视图时将不起作用)

问题描述

When I add my slider as subview of any view besides self.view it does not work (doesn't slide) but it works fine when it is a subview of self.view. You can see it on the other views besides self.view but it doesn't work.

Here is my code:

alphaSlider = [[UISlider alloc] initWithFrame:CGRectMake(0, 0, 90, 10)];
    [alphaSlider setMinimumValue:0.01];
    [alphaSlider setMaximumValue:1];
    [alphaSlider setValue:0.5];
    [alphaSlider setUserInteractionEnabled:YES];
    [alphaSlider addTarget:self action:@selector(alphaSliderDidChange:) forControlEvents:UIControlEventValueChanged];
    alphaSlider.continuous = YES;
[submenu addSubview:alphaSlider];

Any way to fix this?

It may be that submenu is not enabled for user interaction.

[submenu setUserInteractionEnabled:YES];

Another possibility is that the slider's frame is outside of submenu.frame

Since the clipsToBounds property of UIViews is by default NO, the slider would not be clipped despite being outside of submenu's frame. This means that submenu's frame doesn't cover the slider, and there's no way to pass touch events from submenu to submenu's slider. Set the background color of submenu and confirm that the slider is positioned entirely in submenu's frame.

[submenu setBackgroundColor:[UIColor blueColor]];

Submenu's frame might be something like (0, 0, 0, 0).

Include

NSLog(@"%f, %f, %f, %f", submenu.frame.origin.x, submenu.frame.origin.y, submenu.frame.size.width, submenu.frame.size.height);

You could also do

[submenu setClipsToBounds:YES];

and if the slider disappears, then submenu's frame is bad.

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