iphone sdk透明子视图背景

Question

I have a main view with a picture on it.

I am trying to add a subview with [self.view addSubview:view2]; but I want the view2 background to be transparent. Have tried opaque=no and background color to clearcolor and also tried to subclass a uiview and rewrite the drawrect with:

#import "TransparentView.h"


@implementation TransparentView

- (id)initWithFrame:(CGRect)frame 
{
    if (self = [super initWithFrame:frame]) {
        [self setBackgroundColor:[UIColor clearColor]];
        self.opaque=NO;
        self.clearsContextBeforeDrawing=YES;
    }
    return self;
}

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

    CGContextSetFillColorWithColor(context, [UIColor clearColor].CGColor);
    CGContextFillRect(context, rect);
}


@end

But still doesn't display the background of the subview transparent... any ideas?

Answer 1

Try:

view.backgroundColor = [UIColor colorWithWhite:0.0 alpha:0.0];
view.opaque = NO;

Answer 2

Is the view being loaded from a nib file? If so, the -initWithFrame: won't be called; -initWithCoder: will be called instead. A better place to do this initialization might be in -viewDidLoad . But setting the background color to [UIColor clearColor] should definitely do the trick.

Answer 3

Try coloring the subview's background with a 0.0 for Alpha. That should make it completely transparent.

Something like this:

UIColor *myUIColor = [UIColor colorWithRed: 1.0 green: 1.0 blue: 1.0 alpha:0.0];

Answer 4

In the function

- (void)drawRect:(CGRect)rect 

try to update

    CGContextSetFillColorWithColor(context, [UIColor clearColor].CGColor);

to

  const CGFloat BACKGROUND_OPACITY = 0.85; //Note: update this value to what you need 
  CGContextSetRGBFillColor(context, 1, 1, 1, BACKGROUND_OPACITY); // You can change 1,1,1 to the needed values

This link might help you http://www.cocoawithlove.com/2009/04/showing-message-over-iphone-keyboard.html

Answer 5

I've had some cases where ... addSubview:clearView] seemed to reset the background color of clearView ( WTF! ) to something not clear. I added a

[clearView setBackgroundColor:nil];

somewhere after that and it seemed to help.