如何实例化第二个ViewController并停止第一个ViewController的方法

Question

I have a very basic application in which a second ViewController is instantiated if the conditions of an 'if' statement are true. Upon loading of the second ViewController, the methods of the first ViewController still run. I need all previous methods to stop for the application to run correctly.

// In FirstViewController.h

#import <UIKit/UIKit.h>

@interface FirstViewController : UIViewController
{
    NSTimeInterval beginTouchTime;
    NSTimeInterval endTouchTime;
    NSTimeInterval touchTimeInterval;
}

@property (nonatomic, readonly) NSTimeInterval touchTimeInterval;

- (void) testMethod;

@end

// In FirstViewController.m

#import "FirstViewController.h"
#import "SecondViewController.h"

@implementation FirstViewController

@synthesize touchTimeInterval;

- (void)viewDidLoad
{
    [super viewDidLoad]; 
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
}

- (void) testMethod
{
if (touchTimeInterval >= 3)
{
NSLog(@"Go to VC2");
SecondViewController *secondBViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"SecondViewController"];
             [self presentViewController:secondViewController animated:YES completion:nil];
}
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    beginTouchTime = [event timestamp];
    NSLog(@"Touch began");
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    endTouchTime = [event timestamp];
    NSLog(@"Touch ended");

    touchTimeInterval = endTouchTime - beginTouchTime;
    NSLog(@"Time interval: %f", touchTimeInterval);

    [self testMethod]; // EDIT: USED TO BE IN viewDidLoad

}

@end

The second screen successfully loads but the log messages persist, meaning that the methods of FirstViewController still occur, although in the view of the SecondViewController. What am I doing wrong?

Answer 1

看看- (void)viewWillDisappear:(BOOL)animated和- (void)viewDidDisappear:(BOOL)animated您可以在第一个视图控制器上实现这些方法来停止/禁用任何活动或触摸检测。

Answer 2

What you're seeing is the result of the way events are handled in UIKit (check out the "Event Handling Guide for iOS", especially the "Event Delivery: The Responder Chain" section). So what's happening is that since SecondViewController's view doesn't override touchesBegan or touchesEnded, the touch is passed up the responder chain, first to SecondViewController, and then to FirstViewController, which finally does handle those events (FirstViewController is still the window's root view controller after the modal presentation).

Two ways to fix this. You can override touchesBegan and touchesEnded in SecondViewController (or its view I guess), and just have empty methods.

Another way would be to subclass FirstViewController's view, and override the methods there, rather than in the controller. You would still have to do the presentation of SecondViewController from the controller -- you could call a method to do that from the view with [self.nextResponder someMethod].

Answer 3

Is SecondViewController a subclass of FirstViewController? If so the touch events will escalate through the inheritance chain until they are handled. You could override these methods in SecondViewController and have them do nothing (or whatever else you want).