ios - 突出显示（点击）时如何使 UIImageView 变暗？

Question

我有一个显示图片的 UIImageView。当点击并按住时，只要用户将手指放在图像视图上，我希望它变暗。基本上，我希望它像 UIButton 一样。

我目前使用 UIGestureRecognizer 执行此操作：

- (void)viewDidLoad
{
    [super viewDidLoad];

    UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc]
                                         initWithTarget:self
                                         action:@selector(pictureViewTapped)];
    singleTap.numberOfTapsRequired = 1;
    singleTap.numberOfTouchesRequired = 1;
    [self.pictureImageView addGestureRecognizer:singleTap];
    [self.pictureImageView setUserInteractionEnabled:YES];
}

在我的pictureViewTapped，我有这个（现在）：

- (void)pictureViewTapped {
    NSLog(@"Picture view was tapped!");
}

如何使 UIImageView 变暗？任何帮助表示赞赏。

Answer 1

最简单的方法是在 QuartzCore 框架中使用层：

添加：QuartzCore.framework 到您的项目设置中的项目添加到 .h 文件：#import

如您所描述的那样，为长按而不是轻按创建手势：

 self.longTap = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(darkenImage)];
    [self.imageView setUserInteractionEnabled:YES];
    [self.imageView addGestureRecognizer:self.longTap];

手势激活时调用的方法：

-(void)darkenImage {
    switch (self.longTap.state) {
        case UIGestureRecognizerStateBegan: // object pressed
        case UIGestureRecognizerStateChanged:
            [self.imageView.layer setBackgroundColor:[UIColor blackColor].CGColor];
            [self.imageView.layer setOpacity:0.9];
            break;
        case UIGestureRecognizerStateEnded: // object released
            [self.imageView.layer setOpacity:1.0];
            break;
        default: // unknown tap
            NSLog(@"%i", self.longTap.state);
            break;
    }
}

Answer 2

在我的情况下，将 ImageView 的图层不透明度设置为 0.9 时，背景将显示出来。

我使用使用新层的解决方案。

let coverLayer = CALayer()
coverLayer.frame = imageView.bounds;
coverLayer.backgroundColor = UIColor.blackColor().CGColor
coverLayer.opacity = 0.0
imageView.layer.addSublayer(coverLayer)

// when tapped
coverLayer.opacity = 0.1

Answer 3

快速解决方案：

@IBOutlet weak var imageViewExport: UIImageView!
var tapGestureExport = UILongPressGestureRecognizer()

override func viewDidLoad() {
        super.viewDidLoad()

        imageViewExport.userInteractionEnabled = true

        tapGestureExport = UILongPressGestureRecognizer(target: self, action: "tapGestureExportAction:")
        imageViewExport.addGestureRecognizer(tapGestureExport)
    }

    func tapGestureExportAction(sender: UITapGestureRecognizer) {

        switch(tapGestureExport.state) {
        case UIGestureRecognizerState.Began,
                UIGestureRecognizerState.Changed:
            imageViewExport.backgroundColor = UIColor.blackColor()
            imageViewExport.layer.opacity = 0.9

        case UIGestureRecognizerState.Ended:        // released
            imageViewExport.layer.opacity = 1.0

            default: break // unknown tap 
            }
}