Black background on transparent UITabBar

问题

I am trying to make a blurred background the UITabBar for my UITabViewController, and the idea is to have it be blurred and transparent so that the views underneath can be seen scrolling by.

Unfortunately I cannot for the life of me get the tab bar to be transparent. No matter what I do, there is always some black background to the tab bar that prevents the underlying view controllers from showing through.

If I change the alpha of the UITabBar to something low I can see that the tableview is indeed behind it, however you can see that the UITabBar has some sort of background to it that is preventing the tableview from fully showing through (and I don't want to bar button items to be invisible, just the tab bar background).

How can this be?

In the custom tab bar's view did load I have:

self.tabBar.translucent = true
self.tabBar.alpha = 0.3
self.tabBar.backgroundColor = UIColor.clearColor().colorWithAlphaComponent(0.0)
self.tabBar.layer.backgroundColor = UIColor.clearColor().colorWithAlphaComponent(0.0).CGColor
self.tabBar.backgroundImage = nil
self.tabBar.shadowImage = nil

and in the AppDelegate I have:

UITabBar.appearance().barTintColor = UIColor.clearColor()
UITabBar.appearance().tintColor = kColorAccent
UITabBar.appearance().translucent = true
UITabBar.appearance().translucent = true
UITabBar.appearance().backgroundColor = UIColor.clearColor()
UITabBar.appearance().backgroundImage = nil
UITabBar.appearance().layer.backgroundColor = UIColor.clearColor().CGColor
UITabBar.appearance().shadowImage = nil

...yeah It's excessive but I want to try everything.

Any ideas on what to do?

回答1:

Make a UITabBar transparent

Assign a clear image to its backgroundImage. You can use a 1x1 clear.png, or create one programmatically:

self.backgroundImage = UIImage.imageWithColor(UIColor.clearColor())

This will make the UITabBar transparent:

Add a blur effect

Insert a UIVisualEffectView as the rearmost subview.

let frost = UIVisualEffectView(effect: UIBlurEffect(style: .Light))
frost.frame = self.bounds
self.insertSubview(frost, atIndex: 0)

This will insert a UIBlurEffect (frost):

Example

---

1. Set the Custom Class for the UITabBar of the Tab Bar Controller to FrostyTabBar.
2. You have a few options to supply a clearColor image. You can create a clear.png image with an alpha of 0. A programmatic elegant solution is described here.
3. If using a clear.png, assign it to the Background Image in the Attribute Inspector:
4. In Interface Builder, pick Style: Default & Translucent.
5. Once you take control of the background blur with a UIVisualEffectView, you can in turn supply any UIVisualEffect you so desire.

The entire FrostyTabBar class looks like this:

import UIKit

class FrostyTabBar: UITabBar {
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        let frost = UIVisualEffectView(effect: UIBlurEffect(style: .light))
        frost.frame = bounds
        frost.autoresizingMask = .flexibleWidth
        insertSubview(frost, at: 0)
    }
}

---

► Find this solution on GitHub and additional details including a 1x1 clear.png on Swift Recipes.

回答2:

I found a prefect solution, you only need to subclass UITabBar and then do the following actions to clean that annoying views

class MainTabBar: UITabBar {
    var cleanDone = false

    override func layoutSubviews() {
        super.layoutSubviews()
        self.deleteUnusedViews()
    }

    func deleteUnusedViews() {
        if !self.cleanDone {
            var removeCount = 0
            for (_, eachView) in (self.subviews.enumerate()) {
                if NSStringFromClass(eachView.classForCoder).rangeOfString("_UITabBarBackgroundView") != nil {
                    eachView.removeFromSuperview()
                    removeCount += 1
                }
                if NSStringFromClass(eachView.classForCoder).rangeOfString("UIImageView") != nil {
                    eachView.removeFromSuperview()
                    removeCount += 1
                }
                if removeCount == 2 {
                    self.cleanDone = true
                    break
                }
            }
        }
    }
}

回答3:

imageWithColor was replaced by jotImage

let size = CGSize(width: tabBar.bounds.size.width,
                  height: tabBar.bounds.size.height)
tabBar.backgroundImage = UIImage.jotImage(with: UIColor.clear, size: size)

回答4:

the only solution that worked for me was this:

UITabBar.appearance().shadowImage = UIImage()
UITabBar.appearance().backgroundImage = UIImage()

and set: (you can do this in storyboard as well)

UITabBar.appearance().barTintColor = UIColor.clear

but what i have to set in storyboard is:

• tabbar : translucent -> true

来源：https://stackoverflow.com/questions/33819852/black-background-on-transparent-uitabbar