UIPanGestureRecognizer 和 BringSubviewToFront

Question

我有一个应用程序，用户点击一个按钮，应用程序将实例化一个图像层 (UIImageView)。我想这样做，以便用户可以移动选定的图像层，无论他们点击什么。在这里阅读了一些主题后，我了解到我可以使用 UIPanGestureRecognizer 来移动选定的图像层。

- (IBAction)buttonClicked:(id)sender {
    imageview = [[UIImageView alloc] initWithFrame:CGRectMake(100, 0, 300, 22)];
    UIPanGestureRecognizer *imageviewGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(recognizePan:)];
    [imageviewGesture setMinimumNumberOfTouches:1];
    [imageviewGesture setMaximumNumberOfTouches:1];
    imageview.image = [UIImage imageNamed:@"pinimage.png"];
    [imageview addGestureRecognizer:imageviewGesture];
    [imageview setUserInteractionEnabled:YES];
    [self.view addSubview:imageview];
    NSUInteger currentag = [self UniqueTag]; // Assigning a unique integer
    imageview.tag = currentag;
}

- (void)recognizePan:(UIPanGestureRecognizer *)sender {
    [[[(UITapGestureRecognizer *)sender view] layer] removeAllAnimations];
    [self.view bringSubviewToFront:[(UIPanGestureRecognizer *)sender view]];
    CGPoint translatedPoint = [(UIPanGestureRecognizer *)sender translationInView:self.view];

    if([(UIPanGestureRecognizer *)sender state] == UIGestureRecognizerStateBegan) {     
        firstX = [[sender view] center].x;
        firstY = [[sender view] center].y;
    }

    translatedPoint = CGPointMake(firstX + translatedPoint.x,firstY + translatedPoint.y);
    [[sender view] setCenter:translatedPoint];
}

现在，我想不通的是，当有多个图像层时，如何将点击的层放在前面。 [self.view bringSubviewToFront:[(UIPanGestureRecognizer *)sender view]] 似乎没有效果。那么我该如何修改我的代码，以便应用程序将点击层带到顶部呢？

感谢您的帮助。

Answer 1

一个好的方法是创建 UIImageView 的 CustomImageView 子类。您将 UIPanGestureRecognizer 附加到 CustomImageView 的每个实例，并将该实例设置为它的目标。然后手势触发的action方法是在view本身实现的，这样就可以用self引用view：

在buttonClicked

    MyImageView* imageview = [[MyImageView alloc] initWithFrame:CGRectMake(100, 0, 300, 22)];
    UIPanGestureRecognizer *imageviewGesture = 
    [[UIPanGestureRecognizer alloc] initWithTarget:imageview 
                                            action:@selector(recognizePan:)];

在CustomImageView.m

    - (void)recognizePan:(UIPanGestureRecognizer *)sender {
        [self.layer removeAllAnimations];
        [self.superview bringSubviewToFront:self];
        CGPoint translatedPoint = [sender translationInView:self];
        if([sender state] == UIGestureRecognizerStateBegan) {
            self.firstX = [self center].x;
            self.firstY = [self center].y;
        }
        translatedPoint = CGPointMake(self.firstX + translatedPoint.x,
                                      self.firstY + translatedPoint.y);
        [self setCenter:translatedPoint];
    }

更新

不能直截了当 - 您当然可以从 viewController 执行此操作，就像您正在做的那样，通过访问gestureRecongnizer 的view 属性。你的错误就在这里：

- (void)recognizePan:(UIPanGestureRecognizer *)sender {
     [[[(UITapGestureRecognizer *)sender view] layer] removeAllAnimations];

您正在将发件人类型从 UIPanGestureRecognizer 更改为 UITapGestureRecognizer。事实上，您不需要在方法体中进行任何 sender 类型转换。