UIAlertView在iPhone中被称为Twice [重复]

Question

可能重复：
UITableViewCell上的UILongPressGestureRecognizer-双击

我是iPhone新手，

长按Button时会显示Alert，但是长按Button时会再次调用我的警报视图。

这是我的代码段，

- (IBAction)longPressDetected:(UIGestureRecognizer *)gestureRecognizer {

    //Gets text of Button.
    UIButton *btn = (UIButton *)[gestureRecognizer view];
    BtnText= [btn titleForState:UIControlStateNormal];
    NSLog(@"longPressDetected");

    UIAlertView* alert_view = [[UIAlertView alloc]
                               initWithTitle: @"Are you sure want to Delete ?" message:nil delegate: self 
                               cancelButtonTitle: @"Yes" otherButtonTitles: @"No", nil];
    [alert_view show];
    [alert_view release];
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{ 
    if (buttonIndex==0) {

        [self ReloadView];
         [alertView dismissWithClickedButtonIndex:0 animated:TRUE];
    }
    else{
        [alertView dismissWithClickedButtonIndex:1 animated:TRUE];
    }
}

任何帮助将不胜感激。

编辑：

  -(void)viewWillAppear:(BOOL)animated
   {
         for(int i=0;i<10i++)
            {

                if(i!=0)
                {
                    if (i%4==0) 
                    {                    
                        ypos+=180;
                        xpos=30;
                    }
                    else
                    {
                        xpos+=200;
                    }
                }


                button = [UIButton buttonWithType:UIButtonTypeCustom];
                button.frame = CGRectMake(xpos, ypos, 120,130);
                [button setBackgroundImage:[UIImage imageNamed:@"ibook2.png"] forState:UIControlStateNormal];
                [button setTitle:[NSString stringWithFormat:@"%@", [Downloadedepubs objectAtIndex:i]] forState:UIControlStateNormal];
                [button addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];

                 LongPress = [[UILongPressGestureRecognizer alloc] init];
                [LongPress addTarget:self action:@selector(longPressDetected:)];
                 LongPress.delegate = (id<UIGestureRecognizerDelegate>)self;
                [button addGestureRecognizer:LongPress];
                [self.view addSubview:button];
                [LongPress release];

      } 

   }

Answer 1

UILongPressGestureRecognizer是一个长事件过程。 请检查事件状态是否已经开始，完成等。

- (IBAction)longPressDetected:(UIGestureRecognizer *)gestureRecognizer {        

    if (gestureRecognizer.state == UIGestureRecognizerStateBegan){

        NSLog(@"Long press began");

    } else if ( gestureRecognizer.state == UIGestureRecognizerStateRecognized ) {

            NSLog(@"Long press UIGestureRecognizerStateRecognized");
    }
    else if (gestureRecognizer.state == UIGestureRecognizerStateEnded) {

        NSLog(@"Long press Ended");
    }
    else {

        NSLog(@"Long press detected.");
    }       
}

我认为，最好在您的情况下使用UIGestureRecognizerStateBegan状态。

请修改您的longPressDetected()为

 -(IBAction)longPressDetected:(UIGestureRecognizer *)gestureRecognizer {

   if (gestureRecognizer.state == UIGestureRecognizerStateBegan){

       UIButton *btn = (UIButton *)[gestureRecognizer view];
       BtnText= [btn titleForState:UIControlStateNormal];
       NSLog(@"longPressDetected");

      UIAlertView* alert_view = [[UIAlertView alloc] initWithTitle: @"Are you sure want to Delete ?" message:nil delegate: self cancelButtonTitle: @"Yes" otherButtonTitles: @"No", nil];
      [alert_view show];
      [alert_view release];
      alert_view = nil;

   }
 }

请检查以下所有UIGestureRecognizerStates

    UIGestureRecognizerStatePossible,   // the recognizer has not yet recognized its gesture, but may be evaluating touch events. this is the default state

    UIGestureRecognizerStateBegan,      // the recognizer has received touches recognized as the gesture. the action method will be called at the next turn of the run loop
    UIGestureRecognizerStateChanged,    // the recognizer has received touches recognized as a change to the gesture. the action method will be called at the next turn of the run loop
    UIGestureRecognizerStateEnded,      // the recognizer has received touches recognized as the end of the gesture. the action method will be called at the next turn of the run loop and the recognizer will be reset to UIGestureRecognizerStatePossible
    UIGestureRecognizerStateCancelled,  // the recognizer has received touches resulting in the cancellation of the gesture. the action method will be called at the next turn of the run loop. the recognizer will be reset to UIGestureRecognizerStatePossible

    UIGestureRecognizerStateFailed,     // the recognizer has received a touch sequence that can not be recognized as the gesture. the action method will not be called and the recognizer will be reset to UIGestureRecognizerStatePossible

    // Discrete Gestures – gesture recognizers that recognize a discrete event but do not report changes (for example, a tap) do not transition through the Began and Changed states and can not fail or be cancelled
    UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded // the recognizer has received touches recognized as the gesture. the action method will be called at the next turn of the run loop and the recognizer will be reset to UIGestureRecognizerStatePossible

Answer 2

您甚至可以无需输入UILongPressGestureRecognizer详细信息即可执行一些简单的操作来解决此问题。 定义一个BOOL isShowingAlertView 。 调用[alertView show] ，设置isShowingAlertView = YES ，而关闭它时，则设置isShowingAlertView = NO 。 在调用之前，您只需要检查： if (isShowingAlertView == NO) ，则只有它显示：

-(void)viewDidLoad
{
    [super viewDidLoad];
    isShowingAlert = NO;
}

- (IBAction)longPressDetected:(UIGestureRecognizer *)gestureRecognizer {

    if (isShowingAlert == NO)
    {
        isShowingAlert = YES;
        //Gets text of Button.
        UIButton *btn = (UIButton *)[gestureRecognizer view];
        BtnText= [btn titleForState:UIControlStateNormal];
        NSLog(@"longPressDetected");

        UIAlertView* alert_view = [[UIAlertView alloc]
                               initWithTitle: @"Are you sure want to Delete ?" message:nil delegate: self 
                               cancelButtonTitle: @"Yes" otherButtonTitles: @"No", nil];
        [alert_view show];
        [alert_view release];
    }
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
    isShowingAlert = NO;
    if (buttonIndex==0)
    {
        [self ReloadView];
    }
}