Question

我对Objective-C开发相当新。在我从头开始构建的第一个应用程序中，我想绘制一个随着时间的推移增加其大小的圆圈。问题是我能够将圆圈移动到屏幕上，但似乎无法更新其属性，因此它会变得更大或更小。

事情是这样的：

CCircle class

@interface CCircle : CShapes

@property float radius;
@property float startAngleRadians;
@property float endAngleRadians;

在第一个视图控制器（ShapesViewController.m）中：

- (void) viewDidLoad
{
    (...)
    CCircle* circle = [[CCircle alloc] initWithFrame:frame];
    circle.radius = 40;
    circle.startAngleRadians = M_PI;
    circle.endAngleRadians = 2*M_PI;
    circle.tag = 1;
    [self.view addSubView:circle];

    //I also schedule an update method, so that it is called every 1 seconds.
    [NSTimer scheduledTimerWithTmieInterval:1.0 target:self selector:@selector(updateCircle) userInfo:nil repeats:YES];
}

同样在ShapesViewController.m中，更新方法：

- (void) updateCircle
{
    CCircle *circle = [self.view viewWithTag:1];

    //Now here: if I do this: the circle will "move" through the screen
    CGRect frame = circle.frame;
    frame.origin.x += 5;
    [circle setFrame:frame];

    //However, if I try to change the circle properties, I don't know what to do so 
    //that affects the circle. In this case, the circle will move through the screen, 
    //but I keep seeing always the same size(radius).
    circle.radius += 5;

    //I've tried the following (of course, not all at the same time):
    //[self.vew addSubview:circle];
    //[self.view sendSubviewToBack:circle];
    //[self.view sendSubviewToFront:circle];
    //[self.view setNeedsDisplay];
    //[self.view setNeedsLayout];
}

对我做错了什么有帮助，我该怎么做才能实现我的目标？

谢谢！

Answer 1

绘制圆圈后，您必须更新视图。

[self.view setNeedsDisplay];

我认为那样做。

Answer 2

您更新了circle而非self.view的属性，因此您需要在setNeedsDisplay上致电circle。

如何更新View Controller中的元素

2 个答案: