Question

我试图在滚动视图中绘制水平导航菜单。对于菜单中的每一项目, 我有一个不同的图像。当我选择一个项目时, 我想更改此项目的背景图像, 但是我不知道为什么我的代码不起作用 :

for (int i=0; i<12; i++) {
            UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
            UIImage *normal=[UIImage imageNamed:@"icon1"];
            UIImage *selec=[UIImage imageNamed:@"icon1down"];
            [btn setFrame:CGRectMake(i*larg, 0, 42.0, 43.0)];
            [btn setBackgroundImage:normal forState:UIControlStateNormal];
            [btn setBackgroundImage:selec forState:UIControlStateSelected];

            [scrollCat addSubview:btn];
            cx+=42.0;
    }
    [scrollCat setContentSize:CGSizeMake(cx, 43)];

代码里有坏东西吗?

Answer 1

Try UIControlStateHighlighted instead of UIControlStateSelected. Highlighted is the state when the user touches your button. Selected is only used for some controls, like segments ; a custom button (one that say, stays selected) would/could make use of Selected.

从UI control_Class docs at developers.appl.com (强调地雷):

<强度 > UI 控制国光线

Highlighted state of a control. A control enters this state when a touch enters and exits during tracking and when there is a touch up event. ...

<强度 > 联合情报控制国

Selected state of a control. For many controls, this state has no effect on behavior or appearance. But other subclasses (for example, the UISegmentedControl class) may have different appearance depending on their selected state. ...

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