如何正确实现可拖动的“抽屉”自定义 UIView

Question

我的视图控制器底部有一个自定义UIView，它充当“抽屉”控件。大约 90 像素的视图是可见的。当用户点击视图时，它会向上动画显示其他选项、​​控件等。再次点击后，视图会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);
    }
}

所有这些都按预期工作。但是，视图无法正确响应快速“轻弹”手势。在touchesEnded:withEvent: 方法中，我正在为用户将手指举到目的地的视图设置动画。如果用户缓慢拖动然后释放，这很有效。但是如果他们快速轻弹，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。这是所有自定义视图的代码：

-(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];
        }
    }
}

如何正确响应与“抽屉”视图相关的手势？有没有实现这种功能的标准方法？

Answer 1

使用手势识别器而不是自己实现触摸处理代码。您可以同时附加滑动手势识别器和平移手势识别，并设置平移手势，以便在触发平移之前滑动必须失败。使滑动手势的动画更快。像 0.1 或 0.2 秒这样的时间可能适合滑动手势。

不过需要注意的是：在 iOS 7 中，从屏幕底部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 有一个控制抽屉，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向上滑动我们的控制抽屉。我们有一个用于拖动的“拇指”区域，并且我们正在添加一个点击手势，它将在一个步骤中完全显示/隐藏它。