如何正确实现可拖拽的“抽屉”自定义UIView

Question

我在视图控制器的底部有一个自定义的UIView，它充当一个“抽屉”控件。视图的大约90个像素是可见的。当用户点击视图时，它会向上显示其他选项、控件等。再次点击后，视图会向下动画回到其原始位置。有效地“关闭抽屉”。

我还实现了代码，以便视图可以通过拖动手势进行跟踪：

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

    if(self.frame.origin.y >= 80) {
        UITouch *theTouch = [touches anyObject];
        CGPoint location = [theTouch locationInView:self];
        CGPoint previousLocation = [theTouch previousLocationInView:self];
        CGFloat target = location.y - previousLocation.y;
        self.frame = CGRectOffset(self.frame, 0, target);
    }
}

所有这些都像预期的那样工作。但是，视图不能正确响应快速的“轻击”手势。在touchesEnded:withEvent:方法中，我对用户将手指指向其目的地的位置进行了动画处理。如果用户拖得很慢，然后松开，这样做效果很好。但如果它们快速闪烁，视图仍然需要处理0.5秒的持续时间，这对眼睛来说并不平滑。下面是自定义视图的所有代码：

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

    if(self.frame.origin.y >= 80) {
        UITouch *theTouch = [touches anyObject];
        CGPoint location = [theTouch locationInView:self];
        CGPoint previousLocation = [theTouch previousLocationInView:self];
        CGFloat target = location.y - previousLocation.y;
        self.frame = CGRectOffset(self.frame, 0, target);
    }
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    if(self.frame.origin.y == kDefaultUpY) {
        _comingFromUp = YES;
        _comingFromDown = NO;
    }
    else if(self.frame.origin.y == kDefaultDownY) {
        _comingFromUp = NO;
        _comingFromDown = YES;
    }
}

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

    //responding to tap
    if(self.frame.origin.y == kDefaultUpY) {
        [UIView animateWithDuration:0.5f delay:0.0f usingSpringWithDamping:0.75f initialSpringVelocity:1.0f options:UIViewAnimationOptionCurveEaseIn animations:^{
            self.frame = CGRectMake(0, kDefaultDownY, self.frame.size.width, self.frame.size.height);
        } completion:nil];

        return;
    }
    else if(self.frame.origin.y == kDefaultDownY) {
        [UIView animateWithDuration:0.5f delay:0.0f usingSpringWithDamping:0.75f initialSpringVelocity:1.0f options:UIViewAnimationOptionCurveEaseIn animations:^{
            self.frame = CGRectMake(0, kDefaultUpY, self.frame.size.width, self.frame.size.height);
        } completion:nil];

        return;
    }

    //responding to drag
    if(_comingFromDown) {
        if(self.frame.origin.y < kDefaultDownY) {
            //dragging up -- go up
            [UIView animateWithDuration:0.5f delay:0.0f usingSpringWithDamping:0.75f initialSpringVelocity:1.0f options:UIViewAnimationOptionCurveEaseIn animations:^{
                self.frame = CGRectMake(0, kDefaultUpY, self.frame.size.width, self.frame.size.height);
            } completion:nil];
        }
        else if(self.frame.origin.y > kDefaultDownY) {
            //dragging down -- stay down
            [UIView animateWithDuration:0.5f delay:0.0f usingSpringWithDamping:0.75f initialSpringVelocity:1.0f options:UIViewAnimationOptionCurveEaseIn animations:^{
                self.frame = CGRectMake(0, kDefaultDownY, self.frame.size.width, self.frame.size.height);
            } completion:nil];
        }
    }
    else if(_comingFromUp) {
        if(self.frame.origin.y < kDefaultUpY) {
            //dragging up -- stay up
            [UIView animateWithDuration:0.5f delay:0.0f usingSpringWithDamping:0.75f initialSpringVelocity:1.0f options:UIViewAnimationOptionCurveEaseIn animations:^{
                self.frame = CGRectMake(0, kDefaultUpY, self.frame.size.width, self.frame.size.height);
            } completion:nil];
        }
        else if(self.frame.origin.y > kDefaultUpY) {
            //dragging down -- go down
            [UIView animateWithDuration:0.5f delay:0.0f usingSpringWithDamping:0.75f initialSpringVelocity:1.0f options:UIViewAnimationOptionCurveEaseIn animations:^{
                self.frame = CGRectMake(0, kDefaultDownY, self.frame.size.width, self.frame.size.height);
            } completion:nil];
        }
    }
}

如何正确地响应与“折叠式”视图关联的手势？有没有一种标准的方法来实现这种功能？

Answer 1

使用手势识别器，而不是自己实现触摸处理代码。您可以附加一个滑动手势识别器和一个平移手势识别器，并设置平移手势，以便在触发平移之前滑动必须失败。使划动手势的动画速度更快。像0.1秒或0.2秒这样的时间可能是正确的滑动手势。

不过，需要注意的是:在iOS 7中，屏幕底部的滑动手势会触发系统设置抽屉从屏幕底部弹出。我们的应用程序Face Dancer有一个控件抽屉，我们最近发现在iOS 7下很难在不触发系统设置抽屉的情况下将控件抽屉向上滑动。我们有一个用于拖动的“拇指”区域，我们正在添加一个点击手势，它将在一步中完全显示/隐藏它。