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我通过使用类别来做视差效果：

    add and UIView into the uitableView (via category
    add addObserver:forKeyPath so that whenever tableview is moving, i will reframe the view above

详情如下 UIScrollView+Parallax.h

    #import <UIKit/UIKit.h>

    @class ParallaxView;
    @interface UIScrollView (Parallax)

    @property (strong, nonatomic)   ParallaxView    *parallaxView;
    - (void) addParallaxViewWith:(UIView*)parallaxView;
    - (void) removeKVO;

    @end


    @interface ParallaxView : UIView

    @end

UIScrollView+视差.m

static char parallaxKey;
    @implementation UIScrollView (Parallax)
    @dynamic parallaxView;


    #pragma mark - Add parallax view to scrollView
    - (void) addParallaxViewWith:(ParallaxView*)pView {
        if ( !self.parallaxView) {

            [self addSubview:pView];
            [self setParallaxView:pView];
        }

    }

    #pragma mark - Set parallaxView + register parallaxView as an observer
    - (void) setParallaxView:(ParallaxView *)parallaxView {
        objc_setAssociatedObject(self, &parallaxKey, parallaxView, OBJC_ASSOCIATION_ASSIGN);
    /* THESE LINE ARE CRASHING THE APP */
    //    [self addObserver:self.parallaxView
    //           forKeyPath:@"contentOffset"
    //              options:NSKeyValueObservingOptionNew
    //              context:nil];
    }

    #pragma mark - Get parallaxView
    - (ParallaxView*) parallaxView {
        return (objc_getAssociatedObject(self, &parallaxKey));
    }
    #pragma mark - Remove 
    - (void)removeKVO {
            [self removeObserver:self.parallaxView forKeyPath:@"contentOffset"];
    }

    @end

    @implementation ParallaxView

    -(id)init
    {
        //load xib from main bundle and assign it to self
        self = [[[NSBundle mainBundle]loadNibNamed:@"Parallex"
                                             owner:self
                                           options:nil] objectAtIndex:0];

        return self;
    }

    -(id)initWithFrame:(CGRect)frame
    {
        self = [self init];
        [self setFrame:frame];

        return self;
    }

   ................

    @end

我正在通过执行向表格添加视差

ParallaxView *pView = [[ParallaxView alloc]initWithFrame:CGRectMake(0, 0, 320, 160)];

[self.tableView addParallaxViewWith:pView];

但是，[self addObserver:forKeyPath:options:context:nil]在没有任何线索的情况下不断使应用程序崩溃。如果我将此行注释掉并且应用程序没有崩溃但平行效果不起作用。

对此问题的任何想法。请帮忙。谢谢

4

2 回答 2

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代码中的问题

 -(id)initWithFrame:(CGRect)frame
    {
        self = [self init];
        [self setFrame:frame];

        return self;
    }

在上面的代码中 self = [self init]; 和 [self setFrame:frame]; 递归会崩溃，首先解决这个问题我想它会解决你的问题，应该是这样的

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}

并且还使用从笔尖加载视图

self = [[[NSBundle mainBundle]loadNibNamed:@"Parallex"
                                             owner:self
                                           options:nil] objectAtIndex:0];

这段代码真的是个坏主意。你可以参考这个来完成这个任务。快乐而干净的编码...

于 2014-03-25T05:16:47.727 回答
0 
@implementation ParallaxView

//Add Observe Method
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
    if([keyPath isEqualToString:@"contentOffset"]){
        NSLog(@"contentOffset:%@", [change objectForKey:NSKeyValueChangeNewKey]);
    }
}

@end

尝试更换

 objc_setAssociatedObject(self, &parallaxKey, parallaxView, OBJC_ASSOCIATION_ASSIGN);

和

//Change to OBJC_ASSOCIATION_RETAIN_NONATOMIC
objc_setAssociatedObject(self, &parallaxKey, parallaxView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

parallaxView应该是一个强有力的参考。

于 2014-03-25T04:07:09.060 回答