ios - Touch drag enter 如何工作？

Question

谁能给我一个关于 Touch drag enter 从一个按钮拖动到另一个触发两个按钮事件的例子。它是如何工作的？

比如我想从Do拖到Fa，触发Do、Re、Mi、Fa的事件。

这是我的代码:

- (void) setupVC {
soundBankPlayer = [[SoundBankPlayer alloc] init];
[soundBankPlayer setSoundBank:@"Piano"];
arrMusicalNotes = [NSArray arrayWithObjects:@"60", @"62", @"64", @"65", @"67", @"69", @"71", @"72", nil];
}


#pragma mark - Setup Musical Note
- (IBAction)btnMusicalNoteclick:(id)sender {
    int numOfNote = [[arrMusicalNotes objectAtIndex:((UIButton*)sender).tag] intValue];
    NSLog(@"%i", numOfNote);
    [soundBankPlayer queueNote:numOfNote gain:1.0f];
    [soundBankPlayer playQueuedNotes];
}

- (IBAction)btnDragOut:(id)sender {
    NSLog(@"Out");
}

哦，我已经看到，当我在模拟器外按住鼠标不放时，会触发 btnDragOut 方法。当我从 Simulator 拖到按钮时，会触发此按钮的方法。现在我希望当我拖出按钮时触发 btnDragOut 方法(手指仍在模拟器中)。有人知道吗？

Answer 1

您可以通过 Storyboard 或 viewDidLoad 方法中的代码将 UIPanGestureRecognizer 添加到您的 UIViewController 子类的 View 中:

UIPanGestureRecognizer *gestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handleDrag:)];
[self.view addGestureRecognizer:gestureRecognizer];

然后你可以在当前 UIButton 被拖动的 UIViewController 子类的实现文件中添加属性:

@interface YourViewController ()
@property (weak, nonatomic) UIButton *currentButton;
@end

现在在操作方法中，您可以检测 UIControlEventTouchDragEnter 和 UIControlEventTouchDragExit 事件，如下所示:

- (void)handleDrag:(UIPanGestureRecognizer *)gestureRecognizer
{
    CGPoint point = [gestureRecognizer locationInView:self.view];
    UIView *draggedView = [self.view hitTest:point withEvent:nil];

    if (gestureRecognizer.state == UIGestureRecognizerStateChanged) {
        if ([draggedView isKindOfClass:[UIButton class]] && !self.currentButton) {
            self.currentButton = (UIButton *)draggedView;
            NSLog(@"Enter: %ld", (long)self.currentButton.tag);

            // send enter event to your button
            [self.currentButton sendActionsForControlEvents:UIControlEventTouchDragEnter];
        }

        if (self.currentButton && ![self.currentButton isEqual:draggedView]) {
            NSLog(@"Out: %ld", (long)self.currentButton.tag);

            // send exit event to your button
            [self.currentButton sendActionsForControlEvents:UIControlEventTouchDragExit];
            self.currentButton = nil;
        }
    } else if (gestureRecognizer.state == UIGestureRecognizerStateEnded) {
        self.currentButton = nil;
    }
}