在obj-c中连续按下按钮时如何重复执行动作 [英] How to repeatedly perform an action when a button is continuously pressed in obj-c

问题描述

我有四个简单的方法，四个按钮和一个对象。

I've got four simple methods, four buttons and one object.

- (IBAction)left:(id)sender{
    object.center = CGPointMake(object.center.x - 5, object.center.y);
}

- (IBAction)right:(id)sender{
    object.center = CGPointMake(object.center.x + 5, object.center.y);
}
- (IBAction)down:(id)sender{
    object.center = CGPointMake(object.center.x, object.center.y + 5);
}
- (IBAction)up:(id)sender{
    object.center = CGPointMake(object.center.x, object.center.y - 5);
}

当我按下一个按钮时，该方法执行一次。连续按下该按钮时，它是相同的。
该怎么办，以便当我连续按下按钮时，我的对象不断向左移动？

When I press a button, the method is executed once. When the button is pressed continuously it's the same. What do I have to do so that when I press the button continuously my object keep moving to the left?

推荐答案

正如@Maudicus所说，您可能需要使用 NSTimer s进行某些操作，以获取连续的按钮按下触发。我要使用的示例是在屏幕上移动对象（因为无论如何都想这样做）。我使用了分级移动，因为我不知道您是否正在编写基于网格的游戏，因此需要精确的5像素移动。只需切出所有stepSize代码，然后将其设置为5即可。

As @Maudicus said, you probably need to do something with NSTimers to get a continuous button press triggering. The example I'm going to use is moving an object on screen (since you want to do that anyway). I've used graded moving because I have no idea whether you are writing a grid-based game and so need exactly 5 pixels of movement. Just cut out all of the stepSize code and set it to 5 if that's what you do.

1. 编写一个计时器回调函数检查是否设置了 BOOL ，如果设置了则继续触发自身：

1. Write a timer callback function which checks whether a BOOL is set and if so keeps triggering itself:

- (void)moveObjectLeft:(NSTimer *)timer
{
    // check the total move offset and/or the X location of the object here
    // if the object can't be moved further left then invalidate the timer
    // you don't need to check whether the button is still being pressed
    //[timer invalidate];
    //return;

    // the object moves gradually faster as you hold the button down for longer
    NSNumber *moveOffset = (NSNumber *)[timer userInfo];
    NSUInteger stepSize = 1;
    if(moveOffset >= 40)
        stepSize = 10;
    else if(moveOffset >= 15)
        stepSize = 5;
    else if(moveOffset >= 5)
        stepSize = 2;

    // move the object
    object.center = CGPointMake(object.center.x - stepSize, object.center.y);

    // store the new total move offset for this press
    moveOffset += stepSize;
    [timer setUserInfo:moveOffset];
}

在当前类中创建一个计时器属性 .h ：

@property (nonatomic, retain) NSTimer *moveTimer;

在您的 .m ：

@synthesize moveTimer;

在按下按钮时创建计时器对象。在 touchesBegan：withEvent：中执行此操作并检查它是否为Touch Down事件，或者将Interface Builder中的Touch Down事件连接到 IBAction 方法。

Create your timer object when the button is pressed. Either do this in touchesBegan:withEvent: and check it's a Touch Down event, or connect the Touch Down event in Interface Builder to an IBAction method.

NSNumber *moveOffset = [NSNumber numberWithUnsignedInt:0];
self.moveTimer =
    [NSTimer
     scheduledTimerWithTimeInterval:0.2
     target:self
     selector:@selector(moveObject:)
     userInfo:moveOffset
     repeats:YES];

释放按钮时（再次使用上述方法之一， touchesEnded：withEvent：进行内部触摸甚至可能进行外部触摸，或者在这两个事件上使用另一个 IBAction ），均无效外部计时器：

When the button is released (using one of the above methods again, touchesEnded:withEvent: for a Touch Up Inside or probably even a Touch Up Outside, or another IBAction on both of those events), invalidate the timer externally:

[self.moveTimer invalidate];
self.moveTimer = nil;

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