Objectivec IOS 中的圆形进度条

发布于11月28日

我想创建一个圆形进度条，如下所示:

循环进度条

我如何使用Objective-C和Cocoa做到这一点？

我是如何开始创建UIView和编辑drawRect的，但我有点不知所措.任何帮助都将不胜感激.

谢谢

推荐答案

基本概念是利用UIBezierPath级的优势.你可以画圆弧，达到你想要的效果.我只有半个小时左右的时间来try 这个，但我的try 就在下面.

非常基本，它只是在路径上使用了一个笔划，但现在我们开始.您可以根据自己的具体需要更改/修改此设置，但执行arc倒计时的逻辑非常相似.

在view类中:

@interface TestView () {
    CGFloat startAngle;
    CGFloat endAngle;
}

@end

@implementation TestView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
        self.backgroundColor = [UIColor whiteColor];

        // Determine our start and stop angles for the arc (in radians)
        startAngle = M_PI * 1.5;
        endAngle = startAngle + (M_PI * 2);

    }
    return self;
}

- (void)drawRect:(CGRect)rect
{
    // Display our percentage as a string
    NSString* textContent = [NSString stringWithFormat:@"%d", self.percent];

    UIBezierPath* bezierPath = [UIBezierPath bezierPath];

    // Create our arc, with the correct angles
    [bezierPath addArcWithCenter:CGPointMake(rect.size.width / 2, rect.size.height / 2) 
                          radius:130 
                      startAngle:startAngle
                        endAngle:(endAngle - startAngle) * (_percent / 100.0) + startAngle
                       clockwise:YES];

    // Set the display for the path, and stroke it
    bezierPath.lineWidth = 20;
    [[UIColor redColor] setStroke];
    [bezierPath stroke];

    // Text Drawing
    CGRect textRect = CGRectMake((rect.size.width / 2.0) - 71/2.0, (rect.size.height / 2.0) - 45/2.0, 71, 45);
    [[UIColor blackColor] setFill];
    [textContent drawInRect: textRect withFont: [UIFont fontWithName: @"Helvetica-Bold" size: 42.5] lineBreakMode: NSLineBreakByWordWrapping alignment: NSTextAlignmentCenter];
}

对于视图控制器:

@interface ViewController () {    
    TestView* m_testView;
    NSTimer* m_timer;
}

@end

- (void)viewDidLoad
{
    // Init our view
    [super viewDidLoad];
    m_testView = [[TestView alloc] initWithFrame:self.view.bounds];
    m_testView.percent = 100;
    [self.view addSubview:m_testView];
}

- (void)viewDidAppear:(BOOL)animated
{
    // Kick off a timer to count it down
    m_timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(decrementSpin) userInfo:nil repeats:YES];
}

- (void)decrementSpin
{
    // If we can decrement our percentage, do so, and redraw the view
    if (m_testView.percent > 0) {
        m_testView.percent = m_testView.percent - 1;
        [m_testView setNeedsDisplay];
    }
    else {
       [m_timer invalidate];
       m_timer = nil;
    }
}