我制作了一个ViewController并设置了NSNotification。 如果我按下按钮，将出现具有不同标签的相同ViewController，另一个视图（子类）也将出现。 但是，即使我删除了NSNotification，NSNotification的调用次数也会被多次调用。
如果我更改了编写NSNotification的位置，则视图（子类）没有出现，有时视图很快就会出现。 （它应该在返回ViewController之前1秒后出现）
为什么以及如何解决？
@implementation aViewController
- (void)viewDidLoad {
[super viewDidLoad];
UIImageView *bgimgV = [[UIImageView alloc]init];
bgimgV.image = [UIImage imageNamed:@"background.png"];
bgimgV.frame = self.view.bounds;
[self.view addSubview:bgimgV];
UIButton* backBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
UIImage *backBtnimg = [UIImage imageNamed:@"button.png"];
[backBtn setBackgroundImage:backBtnimg forState:UIControlStateNormal];
backBtn.frame = CGRectMake(0, 5, 50, 50);
[backBtn addTarget:self action:@selector(backBtnAction:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:backBtn];
UILabel* questLbl = [[UILabel alloc]init];
questLbl.frame = CGRectMake(10, 45, 300, 180);
NSString *string = [NSString stringWithFormat:@"%@",set[0]];
string = [string stringByReplacingOccurrencesOfString:@"\n" withString:@"\n"];
questLbl.text = string;
questLbl.textColor = RGB(10, 10, 10);
questLbl.font = [UIFont fontWithName:@"HiraKakuProN-W6" size:15];
questLbl.numberOfLines = 0;
[self.view addSubview:questLbl];
for(int b = 0; b<3; b++){
answerBtn[b] = [UIButton buttonWithType:UIButtonTypeCustom];
answerBtn[b].frame = CGRectMake(self.view.frame.size.width/2-(576/2)/2, 290+b*65, 576/2, 90/2);
[answerBtn[b] setImage:[UIImage imageNamed
:[NSString stringWithFormat:@"answer%d.png",b+1]] forState:UIControlStateNormal];
answerBtn[b].tag = b;
[answerBtn[b] addTarget:self action:@selector(answerBtn BtnAction:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview: answerBtn[b]];
}
[[NSNotificationCenter defaultCenter]addObserver:self
selector:@selector(addView)
name:@"addView"
object:nil];
}
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
[[NSNotificationCenter defaultCenter] removeObserver:self
name:@"addView"
object:nil];
}
//when press the back button, add view (sub class)
-(void)backBtnAction:(UIButton*)button{
if([APP_DELEGATE questTag] == 0){
}else{
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
appDelegate.questionTag--;
}
[self.navigationController popViewControllerAnimated:YES];
[[NSNotificationCenter defaultCenter] postNotificationName:@"addView"
object:nil];
}
//when press answer button, same ViewController will appear and change the label
-(void)answerBtnAction:(UIButton*)button{
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
appDelegate.questTag++;
double delayInSeconds = 0.3;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
[self changePage];
});
}
-(void)changePage{
aViewController *aVC = [self.storyboard instantiateViewControllerWithIdentifier:@"aVC"];
[self.navigationController pushViewController:aVC animated:YES];
}
//After back to before page, view (subclass) will be appear after 1 second
-(void)addView{
[self performSelector:@selector(viewAppear) withObject:nil afterDelay:1.0];
}
-(void)viewAppear{
self.RecView = [[InsteRecView alloc] initWithFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height)];
[self.view addSubview:self.RecView];
}