手势开始时
在这里我们要根据手势的 beginPoint 判断触发对象是边线还是 UIImageView
// 开始滑动时判断滑动对象是 ImageView 还是 Layer 上的 Line
if (panGesture.state == UIGestureRecognizerStateBegan) {
if (beginPoint.x >= self.cropAreaX - judgeWidth && beginPoint.x <= self.cropAreaX + judgeWidth && beginPoint.y >= self.cropAreaY && beginPoint.y <= self.cropAreaY + self.cropAreaHeight && self.cropAreaWidth >= 50) {
self.activeGestureView = CROPVIEWLEFT;
} else if (beginPoint.x >= self.cropAreaX + self.cropAreaWidth - judgeWidth && beginPoint.x <= self.cropAreaX + self.cropAreaWidth + judgeWidth && beginPoint.y >= self.cropAreaY && beginPoint.y <= self.cropAreaY + self.cropAreaHeight && self.cropAreaWidth >= 50) {
self.activeGestureView = CROPVIEWRIGHT;
} else if (beginPoint.y >= self.cropAreaY - judgeWidth && beginPoint.y <= self.cropAreaY + judgeWidth && beginPoint.x >= self.cropAreaX && beginPoint.x <= self.cropAreaX + self.cropAreaWidth && self.cropAreaHeight >= 50) {
self.activeGestureView = CROPVIEWTOP;
} else if (beginPoint.y >= self.cropAreaY + self.cropAreaHeight - judgeWidth && beginPoint.y <= self.cropAreaY + self.cropAreaHeight + judgeWidth && beginPoint.x >= self.cropAreaX && beginPoint.x <= self.cropAreaX + self.cropAreaWidth && self.cropAreaHeight >= 50) {
self.activeGestureView = CROPVIEWBOTTOM;
} else {
self.activeGestureView = BIGIMAGEVIEW;
[view setCenter:CGPointMake(view.center.x + translation.x, view.center.y + translation.y)];
[panGesture setTranslation:CGPointZero inView:view.superview];
}
}
手势进行时
在这里，如果触发对象是边线，则计算边线需要移动的距离和方向，以及对于边界条件的限制以防止边线之间交叉错位的情况，具体来说就是获得坐标差值，更新 cropAreaX、cropAreaWidth 等值，然后更新 CAShapeLayer 上的空心蒙层。
如果触发对象是 UIImageView 则只需要将其位置进行改变即可。
// 滑动过程中进行位置改变
if (panGesture.state == UIGestureRecognizerStateChanged) {
CGFloat diff = 0;
switch (self.activeGestureView) {
case CROPVIEWLEFT: {
diff = movePoint.x - self.cropAreaX;
if (diff >= 0 && self.cropAreaWidth > 50) {
self.cropAreaWidth -= diff;
self.cropAreaX += diff;
} else if (diff < 0 && self.cropAreaX > self.bigImageView.frame.origin.x && self.cropAreaX >= 15) {
self.cropAreaWidth -= diff;
self.cropAreaX += diff;
}
[self setUpCropLayer];
break;
}
case CROPVIEWRIGHT: {
diff = movePoint.x - self.cropAreaX - self.cropAreaWidth;
if (diff >= 0 && (self.cropAreaX + self.cropAreaWidth) < MIN(self.bigImageView.frame.origin.x + self.bigImageView.frame.size.width, self.cropView.frame.origin.x + self.cropView.frame.size.width - 15)){
self.cropAreaWidth += diff;
} else if (diff < 0 && self.cropAreaWidth >= 50) {
self.cropAreaWidth += diff;
}
[self setUpCropLayer];
break;
}
case CROPVIEWTOP: {
diff = movePoint.y - self.cropAreaY;
if (diff >= 0 && self.cropAreaHeight > 50) {
self.cropAreaHeight -= diff;
self.cropAreaY += diff;
} else if (diff < 0 && self.cropAreaY > self.bigImageView.frame.origin.y && self.cropAreaY >= 15) {
self.cropAreaHeight -= diff;
self.cropAreaY += diff;
}
[self setUpCropLayer];
break;
}
case CROPVIEWBOTTOM: {
diff = movePoint.y - self.cropAreaY - self.cropAreaHeight;
if (diff >= 0 && (self.cropAreaY + self.cropAreaHeight) < MIN(self.bigImageView.frame.origin.y + self.bigImageView.frame.size.height, self.cropView.frame.origin.y + self.cropView.frame.size.height - 15)){
self.cropAreaHeight += diff;
} else if (diff < 0 && self.cropAreaHeight >= 50) {
self.cropAreaHeight += diff;
}
[self setUpCropLayer];
break;
}
case BIGIMAGEVIEW: {
[view setCenter:CGPointMake(view.center.x + translation.x, view.center.y + translation.y)];
[panGesture setTranslation:CGPointZero inView:view.superview];
break;
}
default:
break;
}
}
