cocoa - 当父级不是窗口时，有没有办法获取相对于最里面的 NSView 的坐标？

Question

我对 NSView 有疑问:

想象一个自定义 View ，其中 mouseDown、mouseDrag 和 mouseUp 方法被重写，以便用户可以在屏幕上拖动点 (NSRect)。要拖动它，我需要相对于当前 View 的鼠标坐标。当 View 的父级是窗口时这不是问题，但是当 View 位于另一个 View 内时如何获取它们？

@implementation MyView

- (id)initWithFrame:(NSRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        pointXPosition = 200.0f;
        pointYPosition = 200.0f;

        locked = NO;
    }
    return self;
}

- (void) drawRect:(NSRect)rect {

    NSRect point = NSMakeRect(pointXPosition, pointYPosition, 6.0f, 6.0f);
    [[NSColor redColor] set];
    NSRectFill(point);

}

- (void)mouseDown:(NSEvent *)theEvent {
    NSPoint mousePos = [theEvent locationInWindow];
    NSRect frame = [super frame];
    CGFloat deltaX = mousePos.x - frame.origin.x - pointXPosition;
    CGFloat deltaY = mousePos.y - frame.origin.y - pointYPosition;
    if(sqrtf(deltaX * deltaX + deltaY * deltaY) < 100.0f)
        locked = YES;
}

- (void)mouseUp:(NSEvent *)theEvent {
    locked = NO;
}

- (void)mouseDragged:(NSEvent *)theEvent {

    if(locked) {
        NSPoint mousePos = [theEvent locationInWindow];

        NSRect frame = [super frame];

        CGFloat oldXPos = pointXPosition;
        CGFloat oldYPos = pointYPosition;

        pointXPosition = mousePos.x - frame.origin.x;
        pointYPosition = mousePos.y - frame.origin.y;

        CGFloat rectToDisplayXMin = MIN(oldXPos, pointXPosition);
        CGFloat rectToDisplayYMin = MIN(oldYPos, pointYPosition);

        CGFloat rectWidthToDisplay = MAX(oldXPos, pointXPosition) - rectToDisplayXMin;
        CGFloat rectHeigthToDisplay = MAX(oldYPos, pointYPosition) - rectToDisplayYMin;

        NSRect dirtyRect = NSMakeRect(rectToDisplayXMin,
                                      rectToDisplayYMin,
                                      rectWidthToDisplay + 6.0f,
                                      rectHeigthToDisplay + 6.0f);

        [self setNeedsDisplayInRect:dirtyRect];
    }
}

Answer 1

您不需要手动转换为本地坐标系。您可以通过向 View 发送 convertPoint:fromView: 消息将点转换为本地坐标系。将 nil 作为参数发送给 fromView 将从 View 的父窗口(无论在哪里)转换点。您还可以发送任何其他 View 来获取从该空间转换的坐标:

// convert from the window's coordinate system to the local coordinate system
NSPoint clickPoint = [self convertPoint:[theEvent locationInWindow] fromView:nil];

// convert from some other view's cooridinate system
NSPoint otherPoint = [self convertPoint:somePoint fromView:someSuperview];