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).。我想使它，以便用户可以移动选定的图像层，无论他们点击。在阅读了一些主题后，我了解到我可以使用UIPanGestureRecognizer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，我不明白的是，当有多个图像层时，如何将被点击的图层带到前面。[self.view bringSubviewToFront:(UIPanGestureRecognizer *)发件人视图]似乎并不有效。那么，我如何修改我的代码，以便应用程序将被点击的层带到顶部？

谢谢你的帮助。

Answer 1

这样做的一个好方法是创建一个CustomImageView子类UIImageView。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，在视图本身中实现由手势触发的操作方法，以便您可以使用self引用视图。

在buttonClicked中

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

在CustomImageView.m中

    - (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

不直截了当--您当然可以通过访问viewController的view属性来做到这一点，就像您正在做的那样。你的错误就在这里：

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

您正在将发送方类型从UIPanGestureRecognizer更改为UITapGestureRecognizer。实际上，您不需要在方法的主体中执行任何sender类型转换。