iOS開(kāi)發(fā)中會(huì)使用到自定義UIView，下面是我在學(xué)習(xí)過(guò)程中寫(xiě)的一個(gè)自定義UIView：

#import "BNRHypnosisView.h"

@interface BNRHypnosisView()

@property(nonatomic, strong) UIColor *circleColor;

@end

@implementation BNRHypnosisView

- (void)setCircleColor:(UIColor *)circleColor {
    _circleColor = circleColor;
    [self setNeedsDisplay];
}

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        self.backgroundColor = [UIColor clearColor];
        self.circleColor = [UIColor lightGrayColor];
        //self.userInteractionEnabled = YES; //開(kāi)啟用戶交互仍然不能響應(yīng)touchesBegan事件
    }
    return self;
}

- (void)drawRect:(CGRect)rect {
    CGContextRef cgContext = UIGraphicsGetCurrentContext();

    CGRect bounds = self.bounds;
    CGPoint center;
    center.x = bounds.origin.x + bounds.size.width / 2.0;
    center.y = bounds.origin.y + bounds.size.height / 2.0;

    float maxRadius = hypot(bounds.size.width, bounds.size.height) / 2.0;

    UIBezierPath *path = [[UIBezierPath alloc] init];
    
   for (float currentRadius = maxRadius; currentRadius > 0; currentRadius -=     20) {
        [path moveToPoint:CGPointMake(center.x + currentRadius, center.y)];
        [path addArcWithCenter:center radius:currentRadius startAngle:0.0   endAngle:M_PI*2.0 clockwise:YES];
    }

    [self.circleColor setStroke];

    path.lineWidth = 10.0;

    [path stroke];


    CGContextSaveGState(cgContext);
    CGContextSetShadow(cgContext, CGSizeMake(4, 7), 3);

    UIImage *logoImage = [UIImage imageNamed:@"logo.png"];

    [logoImage drawInRect:rect];

    CGContextRestoreGState(cgContext);
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent   *)event {

    NSLog(@"%@ was touched", self);

    float red = (arc4random() % 100) / 100.0;
    float green = (arc4random() % 100) / 100.0;
    float blue = (arc4random() % 100) / 100.0;

    UIColor *randomColor = [UIColor colorWithRed:red
                                       green:green blue:blue alpha:1.0];
    self.circleColor = randomColor;
}

@end

在AppDelegate中使用這個(gè)自定義UIView，代碼如下所示：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    NSArray *windows = [[UIApplication sharedApplication] windows];
    for(UIWindow *window in windows) {
        if(window.rootViewController == nil){
            UIViewController *vc = [[UIViewController alloc]initWithNibName:nil
                                                                 bundle:nil];
            window.rootViewController = vc;
        }
    }

    CGRect firstFrame = self.window.bounds;
    BNRHypnosisView *firstView = [[BNRHypnosisView alloc] initWithFrame:firstFrame];

   [self.window addSubview:firstView];


    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}

看似很完美的代碼，但是一運(yùn)行，無(wú)法響應(yīng)touchesBegan事件，開(kāi)始以為是沒(méi)有開(kāi)啟用戶交互，加上開(kāi)啟用戶交互self.userInteractionEnabled = YES，仍然沒(méi)用，后來(lái)有人說(shuō)是這個(gè)自定義UIView視圖被遮擋，導(dǎo)致無(wú)法響應(yīng)觸摸事件，給了我開(kāi)啟視圖調(diào)試器調(diào)試看看的建議，果然，開(kāi)啟視圖調(diào)試器看到這個(gè)自定義UIView確實(shí)被遮擋了，如下圖所示：

viewdebug.png

該怎么解決呢？有人說(shuō)是[self.window makeKeyAndVisible]出了問(wèn)題，他會(huì)把window的rootViewController放到最前面，但我想這肯定是沒(méi)讀懂官方文檔對(duì)makeKeyAndVisible方法的解釋?zhuān)缦聢D所示：

makeKeyAndVisible.png

它是UIWindow對(duì)象的一個(gè)實(shí)例方法，是把當(dāng)前window置于其他window的前面，也就是說(shuō)是把整個(gè)包含了我的自定義UIView的window對(duì)象置于最前面，所以，即使注釋掉這行代碼，仍然無(wú)法解決我的自定義UIView被遮擋的問(wèn)題。

那么問(wèn)題出在哪里呢？對(duì)，問(wèn)題就出在AppDelegate的下面這段代碼中：

NSArray *windows = [[UIApplication sharedApplication] windows];
for(UIWindow *window in windows) {
    if(window.rootViewController == nil){
        UIViewController *vc = [[UIViewController alloc]initWithNibName:nil
                                                                 bundle:nil];
        window.rootViewController = vc; 
    }
}

rootViewController.jpeg

根據(jù)上圖所示官方文檔對(duì)rootViewController的說(shuō)明，可以知道設(shè)置了window.rootViewController會(huì)給window設(shè)定一個(gè)content view。根據(jù)視圖調(diào)試器顯示出來(lái)的內(nèi)容，這個(gè)content view應(yīng)該也就是一個(gè)UIView。所以當(dāng)這個(gè)自定義的UIView添加到self.window上，代碼如下所示：

CGRect firstFrame = self.window.bounds;
BNRHypnosisView *firstView = [[BNRHypnosisView alloc] initWithFrame:firstFrame];

[self.window addSubview:firstView];

這個(gè)自定義UIView就會(huì)被rootViewController設(shè)定的content view遮擋，就不能響應(yīng)觸摸事件了。

因此，解決這個(gè)問(wèn)題修改后的關(guān)鍵代碼如下所示：

CGRect firstFrame = self.window.bounds;
BNRHypnosisView *firstView = [[BNRHypnosisView alloc] initWithFrame:firstFrame];

[self.window.rootViewController.view addSubview:firstView];