在视图接收到手势时做某事

Question

我想在接收 UILongPressGesture 时更改视图 backgroundColor，如何才能正确执行？使用下面的代码，一切都会永远冻结，即使我抬起手指也不会解冻。

- (void)longPress:(UILongPressGestureRecognizer *)gesture {
 while ([gestureRecognizer state] == UIGestureRecognizerStateChanged) {
        [self.Row2View setBackgroundColor:[UIColor colorWithWhite:0.5 alpha:0.2]];
    }
}

编辑我需要的是：当UILongPressGesture改变颜色时，当手指抬起屏幕时改变颜色。

Answer 1

你用while！当进入循环时，条件永远为真！

首先，将 while 更改为 if。然后根据苹果文档：

Long-press gestures are continuous. The gesture begins (UIGestureRecognizerStateBegan) when the number of allowable fingers (numberOfTouchesRequired) have been pressed for the specified period (minimumPressDuration) and the touches do not move beyond the allowable range of movement (allowableMovement). The gesture recognizer transitions to the Change state whenever a finger moves, and it ends (UIGestureRecognizerStateEnded) when any of the fingers are lifted.

我认为你应该使用开始状态（当手势被识别时）或结束状态（当识别的手势释放时）。如果你不想在触摸移动时连续调用方法。

if ([gesture state] == UIGestureRecognizerStateBegan) {
    [self.Row2View setBackgroundColor:[UIColor colorWithWhite:0.5 alpha:0.2]];
}

--- 编辑 ---

根据您的描述，您希望触摸时变色，松开时恢复。所以它将是：

if ([gesture state] == UIGestureRecognizerStateBegan) {
    Row2ViewOriginColor = self.Row2View.backgroundColor; // you can declare this var in the class.
    [self.Row2View setBackgroundColor:[UIColor colorWithWhite:0.5 alpha:0.2]];
}
else if ([gesture state] == UIGestureRecognizerStateEnded ||
         [gesture state] == UIGestureRecognizerStateCancelled) {
    [self.Row2View setBackgroundColor: Row2ViewOriginColor];
}

Answer 2

因为"while"块永远不会破！只需将 "while" 块更改为 "if"!

Answer 3

添加一个属性

@property (copy) UIColor *initialBackgroundColor;

处理长按

- (void)longPress:(UILongPressGestureRecognizer *)gesture
{
    if ([gesture state] == UIGestureRecognizerStateBegan)
    {
        self.initialBackgroundColor = self.Row2View.backgroundColor;
        [self.Row2View setBackgroundColor:[UIColor colorWithWhite:0.5 alpha:0.2]];
    }
    else if ([gesture state] == UIGestureRecognizerStateEnded ||
             [gesture state] == UIGestureRecognizerStateCancelled ||
             [gesture state] == UIGestureRecognizerStateFailed)
    {
        [self.Row2View setBackgroundColor:self.initialBackgroundColor];
    }
}

在视图接收到手势时做某事

Do something While view receives gestures

objective-c

uigesturerecognizer

ios