在CALayer中添加UIImage [英] add UIImage in CALayer

问题描述

我必须添加一个UIImageView作为MapView的子视图。为此，我在MapView上面创建了一个图层。在这一层我想放置我的图像，但我得到一个白色的矩形，没有别的。我的图片不可见。

I must add a UIImageView as subview of MapView. To do this I created a layer above the MapView. In this layer I want to put my image, but I get a white rectangle and nothing else. My image is not visible.

这是代码：

- (void)viewDidLoad
{
    //......

    CALayer *layer = [CALayer layer];
    layer.backgroundColor = [[UIColor whiteColor] CGColor];

    if(UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone)
    {
        layer.bounds = CGRectMake(self.mapView.bounds.origin.x,
                                  self.mapView.bounds.origin.y, 80, 300);
    }
    else
    {
        layer.bounds = CGRectMake(self.mapView.frame.origin.x,
                                  self.mapView.frame.origin.y, 150, 700);
    }

    layer.contents = (id)[UIImage imageNamed:@"myImage.png"];
    //the name is correct but  in the output the image is not visible

    [[self.mapView layer] addSublayer:layer];
    [layer setNeedsDisplay];
}

推荐答案

我删除了

 [layer setNeedsDisplay];

我不知道为什么，但它确实有效！

I do not know why, but it works!

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