NSView子类-drawRect：未调用 [英] NSView subclass - drawRect: not called

问题描述

我创建了一个名为 DAView 的 NSView 子类，其中包含了一系列有用的方法供以后重用。这很好用，但是 drawRect：绝不会在使用 DAView 的任何类中或在类本身中被调用。为什么？

I have created a NSView subclass called DAView, incorporating an array of useful methods for later re-use. This works great, however, drawRect: is never called in any classes that use DAView, nor in the class itself. Why?

这是 DAView 的样子：

DAView

@interface DAView：NSView

- (id)initWithFrame:(NSRect)frame
{
    self = [super initWithFrame:frame];

    if (self)
    {
        self.backgroundColor = [NSColor clearColor];

        // Make layer-backed by default
        self.wantsLayer = YES;

        // Create a root layer
        CALayer *_rootLayer = [CALayer layer];

        _rootLayer.shouldRasterize = YES;

        _rootLayer.name = DAViewRootLayerDefaultName;

        self.layer = _rootLayer;
    }

    return self;
}

- (void)drawRect:(NSRect)dirtyRect // never called
{
    NSLog(@"Draw Rect called");
}

现在，如果我想利用此 DAView的附加方法/方法，我遇到了同样的问题。一切正常，除了 drawRect：，就像在 DAView 的情况下一样，永远不会调用它：

Now, if I wanted to make use of this DAView's additions/methods, I face the same problem. Everything works fine, except for drawRect:, which, as in DAView's case, is never called:

DATableView

@interface DATableView：DAView

- (void)drawRect:(NSRect)dirtyRect // never called either
{
    [[NSColor grayColor] set];

    NSBezierPath *_cellSeparator = [NSBezierPath bezierPath];

    [_cellSeparator lineToPoint:dirtyRect.origin];

    [_cellSeparator closePath];

    [_cellSeparator stroke];

    NSLog(@"Draw rect");
}

但是如果我更改 DATableView 的标题是 NSView 的子类，调用 drawRect：。
我缺少什么？

However If I change DATableView's header to be a subclass of NSView, drawRect: is called. What am I missing?

推荐答案

您必须设置 _rootLayer code>到 self 。

you have to set the delegate of _rootLayer to self.

编辑
对我如何工作：

EDIT How it works for me:

- (id)initWithFrame:(NSRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        self.wantsLayer = YES;
        self.layer = [self makeBackingLayer];
        [self.layer setDelegate:self];
    }

    return self;
}

- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx {
    NSRect rect = self.bounds;
    rect.origin.x = 0;
    rect.origin.y = 0;
    [self drawRect:rect];
}

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