设置背景图像时，未设置UISegmentedControl段宽度

Question

I have a segmented control and I want first and last items to be of specified width (say, wider than others). When I setWidth:forSegmentAtIndex: for standard-styled segmentedControl (ie [[UISegmantedControl appearence] setBackgroundImage:forState:barMetrics:] not set), things behave themselves as they should. But when I set background image, segments width doesn't change.

Here is my code:

[[UISegmentedControl appearance] setBackgroundImage:[[UIImage imageNamed:@"btn_normal.png"] stretchableImageWithLeftCapWidth:25 topCapHeight:0] forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
[[UISegmentedControl appearance] setBackgroundImage:[[UIImage imageNamed:@"btn_selected.png"]  stretchableImageWithLeftCapWidth:25 topCapHeight:0] forState:UIControlStateSelected barMetrics:UIBarMetricsDefault];
[[UISegmentedControl appearance] setDividerImage:[UIImage imageNamed:@"nn.png"] forLeftSegmentState:UIControlStateNormal rightSegmentState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
[[UISegmentedControl appearance] setDividerImage:[UIImage imageNamed:@"sn.png"] forLeftSegmentState:UIControlStateSelected rightSegmentState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
[[UISegmentedControl appearance] setDividerImage:[UIImage imageNamed:@"ns.png"] forLeftSegmentState:UIControlStateNormal rightSegmentState:UIControlStateSelected barMetrics:UIBarMetricsDefault];
[self.segmentedControl setContentMode:UIViewContentModeScaleToFill];
[self.segmentedControl setWidth:100.0 forSegmentAtIndex:0];
[self.segmentedControl setWidth:100.0 forSegmentAtIndex:4];

With this, all my segments appear automatically sized to the equal width.
And when I comment out all above this

[self.segmentedControl setContentMode:UIViewContentModeScaleToFill];
[self.segmentedControl setWidth:100.0 forSegmentAtIndex:0];
[self.segmentedControl setWidth:100.0 forSegmentAtIndex:4];

the sizes are set correctly.
Here is my question: how can I set sizes for the segments with background images?
I'm new to cocoa-touch and objective-c, so I might be missing something...
Could you help please?

Answer 1

I think when you use [UISegmentedControl appearance] proxy it overrides "setWidth:forSegmentAtIndex:" method values. So possible solutions:

1)

[[UISegmentedControl appearance] setContentMode:UIViewContentModeScaleToFill];
[[UISegmentedControl appearance] setWidth:100.0 forSegmentAtIndex:0];
[[UISegmentedControl appearance] setWidth:100.0 forSegmentAtIndex:4];

I would not recommend to use this because it will set custom width for 0 and 4 segments for every segmented control in your app.

2)

[self.segmentedControl setBackgroundImage:[[UIImage imageNamed:@"btn_normal.png"] stretchableImageWithLeftCapWidth:25 topCapHeight:0] forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
[self.segmentedControl setBackgroundImage:[[UIImage imageNamed:@"btn_selected.png"]  stretchableImageWithLeftCapWidth:25 topCapHeight:0] forState:UIControlStateSelected barMetrics:UIBarMetricsDefault];
[self.segmentedControl setDividerImage:[UIImage imageNamed:@"nn.png"] forLeftSegmentState:UIControlStateNormal rightSegmentState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
[self.segmentedControl setDividerImage:[UIImage imageNamed:@"sn.png"] forLeftSegmentState:UIControlStateSelected rightSegmentState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
[self.segmentedControl setDividerImage:[UIImage imageNamed:@"ns.png"] forLeftSegmentState:UIControlStateNormal rightSegmentState:UIControlStateSelected barMetrics:UIBarMetricsDefault];

If you need that all segmented controls in your app should have custom background then I would recommend to write your own proxy method. Something like this:

- (UISegmentedControl *) customSegmentedControl {
    UISegmentedControl *segmentedControl = [ [ [UISegmentedControl alloc] init] autorelease];

    [segmentedControl setBackgroundImage: [ [UIImage imageNamed: @"btn_normal.png"] stretchableImageWithLeftCapWidth: 25 topCapHeight: 0] forState: UIControlStateNormal barMetrics: UIBarMetricsDefault];
    [segmentedControl setBackgroundImage: [ [UIImage imageNamed: @"btn_selected.png"] stretchableImageWithLeftCapWidth: 25 topCapHeight: 0] forState: UIControlStateSelected barMetrics: UIBarMetricsDefault];
    [segmentedControl setDividerImage: [UIImage imageNamed: @"nn.png"] forLeftSegmentState: UIControlStateNormal rightSegmentState: UIControlStateNormal barMetrics: UIBarMetricsDefault];
    [segmentedControl setDividerImage: [UIImage imageNamed: @"sn.png"] forLeftSegmentState: UIControlStateSelected rightSegmentState: UIControlStateNormal barMetrics: UIBarMetricsDefault];
    [segmentedControl setDividerImage: [UIImage imageNamed: @"ns.png"] forLeftSegmentState: UIControlStateNormal rightSegmentState: UIControlStateSelected barMetrics: UIBarMetricsDefault];

    return segmentedControl;
}

Answer 2

我通过编写自定义控件解决了这个问题，基于此http://idevrecipes.com/2010/12/11/custom-segmented-controls/