Set background color for only part of UIView

问题

I want the bottom (not quite half) of my UIView to be a different color than the top.

I'm wondering if I should create a CGRect and then color that? Is this along the right track?

- (void)drawRect:(CGRect)rect { 

    CGRect aRect = CGRectMake(x, y, width, height);

    // Fill the rectangle with grey
    [[UIColor greyColor] setFill];
    UIRectFill( rect );
}

回答1:

Yes, as you are already overriding drawRect method, this will do.

- (void)drawRect:(CGRect)rect { 

    CGRect topRect = CGRectMake(0, 0, rect.size.width, rect.size.height/2.0);
    // Fill the rectangle with grey
    [[UIColor greyColor] setFill];
    UIRectFill( topRect );

    CGRect bottomRect = CGRectMake(0, rect.size.height/2.0, rect.size.width, rect.size.height/2.0);
    [[UIColor redColor] setFill];
    UIRectFill( bottomRect );

}

Change the values inside the frames as you wish.

回答2:

With Swift 5.1 and iOS 13, you may choose one of the two following ways in order to solve your problem.

#1. Draw and fill a specified `CGRect` instance with a `UIColor` instance inside a `UIView` subclass using `UIRectFill(_:)` function

UIKit provides a UIRectFill(_:) function. UIRectFill(_:) has the following declaration:

func UIRectFill(_ rect: CGRect)

Fills the specified rectangle with the current color.

The following Playground code shows how to use UIRectFill(_:):

import UIKit
import PlaygroundSupport

class CustomView: UIView {

    override init(frame: CGRect) {
        super.init(frame: frame)

        backgroundColor = UIColor.green
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func draw(_ rect: CGRect) {
        super.draw(rect)

        let bottomRect = CGRect(
            origin: CGPoint(x: rect.origin.x, y: rect.height / 2),
            size: CGSize(width: rect.size.width, height: rect.size.height / 2)
        )
        UIColor.red.set()
        UIRectFill(bottomRect)
    }

}

let view = CustomView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
PlaygroundPage.current.liveView = view

#2. Draw and fill a specified `CGRect` instance with a `UIColor` instance inside a `UIView` subclass using `CGContext`'s `fill(_:)` method

CGContext has a method called fill(_:). fill(_:) has the following declaration:

func fill(_ rect: CGRect)

Paints the area contained within the provided rectangle, using the fill color in the current graphics state.

The following Playground code shows how to use fill(_:):

import UIKit
import PlaygroundSupport

class CustomView: UIView {

    override init(frame: CGRect) {
        super.init(frame: frame)

        backgroundColor = UIColor.green
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func draw(_ rect: CGRect) {
        super.draw(rect)

        let bottomRect = CGRect(
            origin: CGPoint(x: rect.origin.x, y: rect.height / 2),
            size: CGSize(width: rect.size.width, height: rect.size.height / 2)
        )
        UIColor.red.set()
        guard let context = UIGraphicsGetCurrentContext() else { return }
        context.fill(bottomRect)
    }

}

let view = CustomView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
PlaygroundPage.current.liveView = view

回答3:

You can also add an CALayer as a sub layer to your view. Include CoreGraphics and QuartzCore frameworks and create a CGRect with the desired form factor in your drawRect method. Instantiate a CALayer with the rect and add it to the view's layer using [self.layer addSublayer:theLayer]. Before adding it use the CALayer's -setBackgroundColor: method.

If this is inside of a View Controller instead of a View subclass, do exactly the same in the viewDidLoad method.

Bryan

回答4:

You can use this code. Please change the CGRect according to your desire.

- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();

    CGRect topView = CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height / 2);
    CGRect bottomView = CGRectMake(0, [UIScreen mainScreen].bounds.size.height / 2, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height / 2);

    UIColor * grayColor = [UIColor colorWithRed:230.0/255.0 green:230.0/255.0 blue:230.0/255.0 alpha:1.0];

    CGContextSetFillColorWithColor(context, grayColor.CGColor);
    CGContextFillRect(context, bottomView);

    CGContextSetFillColorWithColor(context, [UIColor yellowColor].CGColor);
    CGContextFillRect(context, topView);
}

The following link may help you more. http://www.raywenderlich.com/32925/core-graphics-tutorial-shadows-and-gloss

回答5:

You can do a CGRect and clip a part of a portion to fill.

But why won't try two different UIViews placed next to each other?

Bharath

回答6:

Override the drawRect method of your UIView Subclass. The following code will make the top half of your view black and the bottom half of your view red.

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Top View
    CGRect topRect = {CGRectGetMinX(self.bounds), CGRectGetMinY(self.bounds), CGRectGetMaxX(self.bounds), CGRectGetMaxY(self.bounds)};
    [[UIColor blackColor] setFill];
    UIRectFill(topRect);

    // Bottom View
    CGRect bottomRect = {CGRectGetMinX(self.bounds), CGRectGetMidY(self.bounds), CGRectGetMaxX(self.bounds), CGRectGetMidY(self.bounds)};
    [[UIColor redColor] setFill];
    UIRectFill(bottomRect);
}

NOTE: Also you can only override the drawRect: method when you subclass a UIView. Based on your comment view I have a feeling this is not what you are doing.

来源：https://stackoverflow.com/questions/18064055/set-background-color-for-only-part-of-uiview

标签

ios

uiview

cgrect

uibackgroundcolor